be demonstrated by good reason to be so CHAP. III. Of Proposition 1 Divers Kinds of Speech 2 Proposition defined 3 Subject Praedicate and Copula what they are and Abstract and Concrete what The Use and Abuse of Names Abstract 5 Proposition Universal and Particular 6 Affirmative and Negative 7 True and False 8 True and False belongs to Speech and not to Things 9 Proposition Primary not Primary Definion Axiome Petition 10 Proposition Necessary and Contingent 11 Categoricall and Hypotheticall 12 The same Proposition diversly pronounced 13 Propositions that may be reduced to the same Categoricall Proposition are Equipollent 14 Universal Propositions converted by Contradictory Names are Equipollent 15 Negative Propositions are the same whether the Negation be before or after the Copula 16 Particular Propositions simply converted are Equipollent 17 What are Subaltern Contrary Subcontrary and Contradictory Propositions 18 Consequence what it is 19 Falsity cannot follow from Truth 20 How one Proposition is the Cause of another 1_FRom the Connection or Contexture of Names arise diverse kinds of Speech whereof some signifie the Desires and Affections of Men such are first Interrogations which denote the desire of Knowing as Who is a good Man In which speech there is one Name expressed another desired and expected from him of whom we aske the same Then Prayers which signifie the desire of having something Promises Threats Wishes Commands Complaints and other significations of other Affections Speech may also be Absurd and Insignificant as when there is a succession of Words to which there can be no succession of Thoughts in the mind to answer them and this happens often to such as understanding nothing in some subtil matter doe neverthelesse to make others beleeve they understand speake of the same incoherently For the connection of incoherent Words though it want the end of Speech which is Signification yet it is Speech and is used by the Writers of Metaphysicks almost as frequently as Speech significative In Philosophy there is but one kinde of Speech usefull which some call in Latine Dictum others Enuntiatum Pronunciatum but most men call it Proposition and is the speech of those that Affirm or Deny and expresseth Truth or Falsity 2 A PROPOSITION is a Speech consisting of two Names copulated by which he that speaketh signifies he conceives the later Name to be the Name of the same thing whereof the former is the Name or which is all one that the former Name is comprehended by the later For example this speech Man is a Living Creature in which two Names are copulated by the verb Is is a Proposition for this reason that he that speakes it conceives both Living Creature and Man to be Names of the same thing or that the former Name Man is comprehended by the later Name Living Creature Now the former Name is commonly called the Subject or Antecedent or the Contained Name and the later the Praedicat Consequent or Containing Name The signe of Connection amongst most Nations is either some word as the word is in the Proposition Man is a living Creature or some Case or Termination of a word as in this Proposition Man walketh which is equivalent to this Man is walking the Termination by which it is said he walketh rather then he is walking signifieth that those two are understood to be copulated or to be Names of the same Thing But there are or certainly may be some Nations that have no word which answers to our Verbe Is who neverthelesse forme Propositions by the position onely of one Name after another as if instead of Man is a Living Creature it should be said Man a Living Creature for the very order of the Names may sufficiently shew their connection and they are as apt and usefull in Philosophy as if they were copulated by the Verbe Is. 3 Wherefore in every Proposition three things are to be considered viz. the two Names which are the Subject and the Praedicate and their Copulation both which Names raise in our Minde the Thought of one and the same Thing but the Copulation makes us thinke of the Cause for which those Names were imposed on that Thing As for example when we say a Body is moveable though we conceive the same thing to be designed by both those Names yet our Minde rests not there but searches further what it is to be a Body or to be Moveable that is wherein consists the difference betwixt these and other Things for which these are so called others are not so called They therefore that seeke what it is to be any thing as to be Moveable to be Hot c. seek in Things the causes of their Names And from hence arises that distinction of Names touched in the last Chap. into Concrete and Abstract For Concrete is the Name of any thing which we suppose to have a being and is therefore called the Subject in Latine Suppositum and in Greek 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 as Body Moveable Moved Figurate a Cubit high Hot Cold Like Equal Appius Lentulus and the like and Abstract is that which in any Subject denotes the Cause of the Concrete Name as to be a Body to be Moveable to be Moved to be Figurate to be of such Quantity to be Hot to be Cold to be Like to be Equall to be Appius to be Lentulus c. Or Names equivalent to these which are most commonly called Abstract Names as Corporeity Mobility Motion Figure Quantity Heat Cold Likenesse Equality and as Cicero has it Appiety and Lentulity Of the same kind also are Infinitives for to Live and to Move are the same with Life and Motion or to be Living and to be Moved But Abstract Names denote onely the Causes of Concrete Names and not the Things themselves For example when we see any thing or conceive in our Minde any Visible thing that Thing appears to us or is conceived by us not in one Point but as having Parts distant from one another that is as being extended and filling some space Seeing therefore we call the Thing so conceived Body the cause of that name is that that Thing is extended or the Extension or Corporeity of it So when we see a Thing appeare sometimes here sometimes there and call it Moved or Removed the Cause of that Name is that it is Moved or the Motion of the same And these Causes of Names are the same with the Causes of our Conceptions namely some Power or Action or Affection of the Thing conceived which some call the Manner by which any thing workes upon our senses but by most men they are called Accidents I say Accidents not in that sense in which Accident is opposed to Necessary but so as being neither the Things themselves nor parts thereof do neverthelesse accompany the Things in such manner that saving Extension they may all perish and 〈◊〉 destroyed but can never be abstracted 4 There is also this difference betwixt Concrete and Abstract Names that those
the Names of the parts of any Speech be explicated is it not necessary that the Definition should be a Name Compounded of them For example when these Names Aequilaterall Quadrilaterall Right-angled are sufficiently understood it is not necessary in Geometry that there should be at all such a Name as Square for defined Names are received in Philosophy for brevities sake onely Fiftly That Compounded Names which are defined one way in some one part of Philosophy may in another part of the same be otherwise defined as a Parabola and an Hyperbole have one Definition in Geometry and another in Rhetorique for Definitions are instituted and serve for the understanding of the Doctrine which is treated of And therefore as in one part of Philosophy a Definition may have in it some one fit Name for the more briefe explanation of some proposition in Geometry so it may have the same liberty in other parts of Philosophy for the use of Names is particular even where many agree to the setling of them and arbitrary Sixtly That no Name can be defined by any one Word because no one Word is sufficient for the Resolving of one or more words Seventhly That a defined Name ought not to be repeated in the Definition For a defined Name is the whole Compound and a Definition is the Resolution of that Compound into parts but no Totall can be part of it selfe 16 Any two Definitions that may be compounded into a Syllogisme produce a Conclusion which because it is derived from Principles that is from Definitions is said to be Demonstrated and the Derivation or Composition it selfe is called a Demonstration In like manner if a Syllogisme be made of two Propositions whereof one is a Definition the other a Demonstrated Conclusion or neither of them is a Definition but both formerly demonstrated that Syllogisme is also called a Demonstration and so successively The Definition therefore of a Demonstration is this A DEMONSTRATION is a Syllogism or Series of Syllogisms derived and continued from the Definitions of Names to the last Conclusion And from hence it may be understood that all true Ratiocination which taketh its beginning from true Principles produceth Science and is true Demonstration For as for the Originall of the Name although that which the Greeks called 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 and the Latines Demonstratio was understood by them for that sort onely of Ratiocination in which by the describing of certaine Lines and Figures they placed the thing they were to prove as it were before mens Eyes which is properly 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 or to shew by the Figure yet they seem to have done it for this reason that unlesse it were in Geometry in which only there is place for such Figures there was no Ratiocination certaine and ending in Science their Doctrines concerning all other things being nothing but Controversie and Clamour which neverthelesse hapned not because the Truth to which they pretended could not be made evident without Figures but because they wanted true Principles from which they might derive their Ratiocination and therefore there is no reason but that if true Definitions were praemised in all sorts of Doctrines the Demonstrations also would be true 17 It is proper to Methodical Demonstration First That there be a true Succession of one Reason to another according to the Rules of Syllogizing delivered above Secondly That the Praemisses of all Syllogismes be demonstrated from the first Definitions Thirdly That after Definitions he that Teaches or Demonstrates any thing proceed in the same Method by which he found it out namely that in the first place those things be demonstrated which immediately succeed to Universal Definitions in which is contained that part of Philosophy which is called Philosophia Prima Next those things which may be demonstrated by Simple Motion in which Geometry consists After Geome try such things as may be taught or shewed by manifest Action that is by Thrusting from or Pulling towards And after these the Motion or Mutation of the invisible parts of Things and the Doctrine of Sense Imagination of the internal Passions especially those of Men in which are comprehended the Grounds of Civil Duties or Civil Philosophy which takes up the last place And that this Method ought to be kept in all sorts of Philosophy is evident from hence that such things as I have said are to be taught last cannot be demonstrated till such as are propounded to be first treated of be fully understood Of which Method no other Example can be given but that Treatise of the Elements of Philosophy which I shall begin in the next Chapter and continue to the end of the worke 18 Besides those Paralogismes whose fault lies either in the Falsity of the Praemisses or the want of true Composition of which I have spoken in the praecedent Chapter there are two more which are frequent in Demonstration one whereof is commonly called Petitio Principii the other is the supposing of a False Cause and these do not onely deceive Unskilfull Learners but sometimes Masters themselves by making them take that for well demonstrated which is not demonstrated at all Petitio Principii is when the Conclusion to be proved is disguised in other Words and put for the Definition or Principle from whence it is to be demonstrated and thus by putting for the Cause of the Thing sought either the Thing it selfe or some Effect of it they make a Circle in their Demonstration As for example He that would Demonstrate that the Earth stands still in the Center of the World and should suppose the Earths Gravity to be the Cause thereof and define Gravity to be a quality by which every heavy Body tends towards the Center of the World would lose his labour for the question is What is the Cause of that quality in the Earth and therefore he that supposes Gravity to be the Cause puts the Thing it selfe for its own Cause Of a False Cause I find this example in a certaine Treatise where the thing to be demonstrated is the Motion of the Earth He begins therefore with this that seeing the Earth and the Sun are not alwayes in the same scituation it must needs be that one of them be locally moved which is true next he affirms that the Vapours which the Sun raises from the Earth and Sea are by reason of this Motion necessarily moved which also is true from whence he infers the Winds are made and this may passe for granted and by these Winds he sayes the Waters of the Sea are moved and by their Motion the bottome of the Sea as if it were beaten forwards moves round and let this also be granted wherefore he concludes the Earth is moved which is neverthelesse is a Paralogisme For if that wind were the Cause why the Earth was from the beginning moved round and the Motion either of the Sunne or the Earth were the Cause of that Wind then the Motion of the Sunne or
end that the Reader may know that those Axioms are not indemonstrable therefore not Principles of Demonstration and from hence learn to be wary how he admits any thing for a Principle which is not at least as evident as these are Greater is defined to be that whose Part is Equal to the Whole of another Now if we suppose any Whole to be A and a Part of it to be B seeing the Whole B is Equal to it self and the same B is a Part of A therefore a Part of A will be Equal to the Whole B. Wherefore by the Definition above A is Greater then B which was to be proved CHAP. IX Of Cause and Effect 1 Action and Passion what they are 2 Action and Passion Mediate and Immediate 3 Cause simply taken Cause without which no Effect follows or Cause Necessary by Supposition 4 Cause Efficient and Material 5 An Entire Cause is alwayes sufficient to produce its Effect At the same instant that the Cause is Entire the Effect is produced Every Effect has a Necessary Cause 6 The Generation of Effects is Continual What is the Beginning in Causation 7 No Cause of Motion but in a Body Contiguous and Moved 8 The same Agents and Patients if alike disposed produce like Effects though at different times 9 All Mutation is Motion 10 Contingent Accidents what they are 1 A Body is said to Work upon or Act that is to say Do some thing to another Body when it either generates or destroys some Accident in it and the Body in which an Accident is generated or destroyed is said to Suffer that is to have something Done to it by another Body As when one Body by putting forwards another Body generates Motion in it it is called the AGENT and the Body in which Motion is so generated is called the PATIENT so Fire that warms the Hand is the Agent and the Hand which is warmed is the Patient That Accident which is generated in the Patient is called the EFFECT 2 When an Agent and Patient are Contiguous to one another their Action and Reason are then said to be Immediate otherwise Mediate and when another Body lying betwixt the Agent and Patient is Contiguous to them both it is then it self both an Agent and a Patient an Agent in respect of the Body next after it upon which it Works and a Patient in respect of the Body next before it from which it suffers Also if many Bodies be so ordered that every two which are next to one another be contiguous then all those that are betwixt the first and the last are both Agents and Patients and the first is an Agent onely and the last a Patient onely 3 An Agent is understood to produce its determined or certain Effect in the Patient according to some certain Accident or Accidents with which both it and the Patient are affected that is to say the Agent hath its Effect precisely such not because it is a Body but because such a Body or so Moved For otherwise all Agents seeing they are all Bodies alike would produce like Effects in all Patients and therefore the Fire for example does not warm because it is a Body but because it is Hot nor does one Body put forward another Body because it is a Body but because it is moved into the place of that other Body The Cause therefore of all Effects consists in certain Accidents both in the Agents and in the Patient which when they are all present the Effect is produced but if any one of them be wanting it is not produced and that Accident either of the Agent or Patient without which the Effect cannot be produced is called Causa sine qua non or Cause Necessary by Supposition as also the Cause Requisite for the Production of the Effect But a CAUSE simply or An Entire Cause is the Aggregate of all the Accidents both of the Agents how many soever they be and of the Patient put together which when they are all supposed to be present it cannot be understood but that the Effect is produced at the same instant and if any one of them be wanting it cannot be understood but that the Effect is not produced 4 The Aggregate of Accidents in the Agent or Agents requisite for the production of the Effect the Effect being produced is called the Efficient Cause thereof and the Aggregate of Accidents in the Patient the Effect being produced is usually called the Material Cause I say the Effect being produced for where there is no Effect there can be no Cause for nothing can be called a Cause where there is nothing that can be called an Effect But the Efficient and Material Causes are both but Partial Causes or Parts of that Cause which in the next precedent article I called an Entire Cause And from hence it is manifest that the Effect we expect though the Agents be not defective on their part may nevertheless be frustrated by a defect in the Patient and when the Patient is sufficient by a defect in the Agents 5 An Entire Cause is alwayes sufficient for the production of its Effect if the Effect be at all possible For let any Effect whatsoever be propounded to be produced if the same be produced it is manifest that the Cause which produced it was a sufficient Cause but if it be not produced and yet be possible it is evident that something was wanting either in some Agent or in the Patient without which it could not be produced that is that some Accident was wanting which was requisite for its Production and therefore that Cause was not Entire which is contrary to what was supposed It follows also from hence that in whatsoever instant the Cause is Entire in the same instant the Effect is produced For if it be not produced something is still wanting which is requisite for the production of it and therefore the Cause was not Entire as was supposed And seeing a Necessary Cause is defined to be that which being supposed the Effect cannot but follow this also may be collected that whatsoever Effect is produced at any time the same is produced by a Necessary Cause For whatsoever is produced in as much as it is produced had an Entire Cause that is had all those things which being supposed it cannot be understood but that the Effect follows that is it had a Necessary Cause And in the same manner it may be shewn that whatsoever Effects are hereafter to be produced shall have a Necessary Cause so that all the Effects that have been or shall be produced have their Ne cessity in things antecedent 6 And from this that whensoever the Cause is Entire the Effect is produced in the same instant it is manifest that Causation and the Production of Effects consist in a certain continual Progress so that as there is a continual Mutation in the Agent or Agents by the working of other Agents upon them so also the Patient upon
which they work is continually altered and changed For example as the Heat of the Fire encreases more and more so also the Effects thereof namely the Heat of such Bodies as are next to it again of such other Bodies as are next to them encreases more more accordingly which is already no litle argument that all Mutation consists in Motion onely the truth whereof shall be further demonstrated in the ninth Article But in this Progress of Causation that is of Action and Passion if any man comprehend in his imagination a part thereof and divide the same into parts the first part or Beginning of it cannot be considered otherwise then as Action or Cause for if it should be considered as Effect or Passion then it would be necessary to consider something before it for its Cause or Action which cannot be for nothing can be before the Beginning And in like manner the last part is considered onely as Effect for it cannot be called Cause if nothing follow it but after the last nothing follows And from hence it is that in all Action the Beginning and Cause are taken for the same thing But every one of the intermediate parts are both Action and Passion and Cause and Effect according as they are compared with the antecedent or subsequent part 7 There can be no Cause of Motion except in a Body Contiguous and Moved For let there be any two Bodies which are not contiguous and betwixt which the intermediate Space is empty or if filled filled with another Body which is at Rest and let one of the propounded Bodies be supposed to be at Rest I say it shall always be at Rest. For if it shall be Moved the Cause of that Motion by the 8th Chapter 19th Article will be in some external Body and therefore if between it and that external Body there be nothing but empty Space then whatsoever the disposition be of that external Body or of the Patient it self yet if it be supposed to be now at Rest we may conceive it wil continue so til it be touched by some other Body but seeing Cause by the Definition is the Aggregate of all such Accidents which being supposed to be present it cannot be conceived but that the Effect will follow those Accidents which are either in external Bodies or in the Patient it self cannot be the Cause of future Motion and in like manner seeing we may conceive that whatsoever is at Rest will still be at Rest though it be touched by some other Body except that other Body be moved therefore in a contiguous Body which is at Rest there can be no Cause of Motion Wherefore there is no Cause of Motion in any Body except it be Contiguous and Moved The same reason may serve to prove that whatsoever is Moved will alwayes be Moved on in the same way and with the same Velocity except it be hindered by some other Contiguous and Moved Body and consequently that no Bodies either when they are at Rest or when there is an interposition of Vacuum can generate or â—â—tinguish or lesson Motion in other Bodies There is one that has written that things Moved are more resisted by things at Rest then by things contrarily Moved for this reason that he conceived Motion not to be so contrary to Motion as Rest. That which deceived him was that the words Rest and Motion are but contradictory Names whereas Motion indeed is not resisted by Rest but by contrary Motion 8 But if a Body work upon another Body at one time and afterwards the same Body work upon the same Body at another time so that both the Agent and Patient and all their parts be in all things as they were and there be no difference except onely in time that is that one Action be former the other later in time it is manifest of it self that the Effects will be Equal and Like as not differing in any thing besides time And as Effects themselves proceed from their Causes so the diversity of them depends upon the diversity of their Causes also 9 This being true it is necessary that Mutation can be nothing else but Motion of the Parts of that Body which is Changed For First we do not say any thing is Changed but that which appears to our Senses otherwise then it appeared formerly Secondly both those Appearances are Effects produced in the Sentient therefore if they be differeÌ„t it is necessary by the preceding article that either some part of the Agent which was formerly at Rest is now Moved and so the Mutation consists in this Motion or some part which was formerly Moved is now otherwise Moved and so also the Mutation consists in this new Motion or which being formerly Moved is now at Rest which as I have shewn above cannot come to pass without Motion and so again Mutation is Motion or lastly it happens in some of these manners to the Patient or some of its parts so that Mutation howsoever it be made will consist in the Motion of the parts either of the Body which is perceived or of the Sentient Body or of both Mutation therefore is Motion namely of the parts either of the Agent or of the Patient which was to be demonstrated And to this it is consequent that Rest cannot be the Cause of any thing nor can any Action proceed from it seeing neither Motion nor Mutation can be caused by it 10 Accidents in respect of other Accidents which precede them or are before them in time upon which they do not depend as upon their Causes are called Contingent Accidents I say in respect of those Accidents by which they are not generated for in respect of their Causes all things come to pass with equal necessity for otherwise they would have no Causes at all which of things generated is not intelligible CHAP. X. Of Power and Act. 1 Power and Cause are the same thing 2 An Act is produced at the same instant in which the Power is Plenary 3 Active and Passive Power are parts onely of Plenary Power 4 An Act when said to be Possible 5 An Act Necessary and Contingent what 6 Active Power consists in Motion 7 Cause Formal and Final what they are 1_COrrespondent to Cause and Effect are POWER and ACT Nay those and these are the same things though for divers considerations they have divers names Forwhensoever any Agent has all those Accidents which are necessarily requisite for the production of some Effect in the Patient then we say that Agent has Power to produce that Effect if it be applyed to a Patient But as I have shewn in the precedent Chapter those Accidents constitute the Efficient Cause and therefore the same Accidents which constitute the Efficient Cause constitute also the Power of the Agent Wherefore the Power of the Agent and the Efficient Cause are the same thing But they are considered with this difference that Cause is so called in respect of the Effect already
same Chapter I have shewn that Whatsoever is at Rest will alwayes be at Rest unless there be some other Body besides it which by getting into its place suffers it no longer to remain at Rest. And that Whatsoever is Moved will alwayes be Moved unless there be some other Body besides it which hinders its Motion Tenthly In the 9 Chapter and 7 Article I have demonstrated that When any Body is moved which was formerly at Rest the immediate efficient cause of that Motion is in some other Moved and Contiguou◠Body Eleventhly I have shewn in the same place that Whatsoever is Moved will always be Moved in the same way and with the same Swiftness if it be not hindered by some other Moved and Contiguou◠Body 2 To which Principles I shall here add these that follow First I define ENDEAVOUR to be Motion made in less Space and Time then can be given that is less then can be determined or assigned by Exposition or Number that is Motion made through the length of a Point and in an Instant or Point of Time For the explayning of which Definition it must be remembred that by a Point is not to be understood that which has no quantity or which cannot by any means be divided for there is no such thing in Nature but that whose quantity is not at all considered that is whereof neither quantity nor any part is computed in demonstration so that a Point is not to be taken for an Indivisible but for an Undivided thing as also an Instant is to be taken for an Undivided and not for an Indivisible Time In like manner Endeavour is to be conceived as Motion but so as that neither the quantity of the Time in which nor of the Line in which it is made may in demonstration be at all brought into comparison with the quantity of that Time or of that Line of which it is a part And yet as a Point may be compared with a Point so one Endeavour may be compared with another Endeavour and one may be found to be greater or lesse then another For if the Vertical points of two Angles be compared they will be equal or unequal in the same proportion which the Angles themselves have to one another Or if a straight Line cut many Circumferences of Concentrick Circles the inequality of the points of intersection will be in the same proportion which the Perimeters have to one another And in the same manner if two Motions begin and end both together their Endeavours will be Equal or Unequal according to the proportion of their Velocities as we see a bullet of Lead descend with greater Endeavour then a ball of Wooll Secondly I define IMPETUS or Quickness of Motion to be the Swiftness or Velocity of the Body moved but considered in the several points of that time in which it is moved In which sense Impetus is nothing else but the quantity or velocity of Endeavour But considered with the whole time it is the whole velocity of the Body moved taken together throughout all the time and equal to the Product of a Line representing the time multiplyed into a Line representing the arithmetically mean Impetus or Quickness Which Arithmetical Mean what it is is defined in the 29th Article of the 13th Chapter And because in equal times the wayes that are passed are as the Velocities and the Impetus is the Velocity they go withal reckoned in all the several points of the times it followeth that during any time whatsoever howsoever the Impetus be encreased or decreased the length of the way passed over shall be encreased or decreased in the same proportion and the same Line shall represent both the way of the Body moved and the several Impetus or degrees of Swiftness wherewith the way is passed over And if the Body moved be not a point but a straight line moved so as that every point thereof make a several straight line the Plain described by its motion whether Uniform Accelerated or Retarded shall be greater or less the time being the same in the same proportion with that of the Impetus reckoned in one motion to the Impetus reckoned in the other For the reason is the same in Parallelograms and their Sides For the same cause also if the Body moved be a Plain the Solid described shall be still greater or less in the proportions of the several Impetus or Quicknesses reckoned through one Line to the several Impetus reckoned through another This understood let ABCD in the first figure of the 17th Chapter be a Parallelogram in which suppose the side AB to be moved parallelly to the opposite side CD decreasing al the way till it vanish in the point C and so describing the figure ABEFC the point B as AB decreaseth will therefore describe the Line BEFC and suppose the time of this motion designed by the line CD and in the same time CD suppose the side AC to be moved parallelly and uniformly to BD. From the point O taken at adventure in the Line CD draw OR parallel to BD cutting the Line BEFC in E and the side AB in R. And again from the point Q taken also at adventure in the Line CD draw QS parallel to BD cutting the Line BEFC in F and the side AB in S and draw EG and FH parallel to CD cutting AC in G and H. Lastly suppose the same construction done in all the points possible of the Line BEFC I sa◠that as the proportions of the Swiftnesses wherewith QF OE DB and all the rest supopsed to be drawn parallel to DB and terminated in the Line BEFC are to the proportions of their several Times designed by the several parallels HF GE AB and all the rest supposed to be drawn parallel to the Line of time CD and terminated in the Line BEFC the aggregate to the aggregate so is the Area or Plain DBEFC to the Area or Plain ACFEB For as AB decreasing continually by the line BEFC vanisheth in the time CD into the point C so in the same time the line DC continually decreasing vanisheth by the same line CFEB into the point B and the point D describeth in that decreasing motion the line DB equall to the line AC described by the point A in the decreasing motion of A B their swiftnesses are therefore equal Again because in the time GE the point O describeth the line OE and in the same time the point R describeth the line RE the line OE shall be to the line RE as the swiftness wherewith OE is described to the swiftness wherwith RE is described In like māner because in the same time HF the point Q describeth the Line QF and the point S the Line SF it shall be as the swiftness by which QF is described to the swiftness by which SF is described so the Line it self QF to the Line it self SF and so in all the Lines that can possibly be
Axis IG the same with BC departed from its own former situation Wherefore in what time BC comes to IG by the motion from B to I upon the center A in the same time G will come to F by the contrary motion of the Epicycle that is it will be turned backwards to F IG will lie in IF But the angles FIG and GAC are equal and therefore AC that is BC and IG that is the Axis though in different places will be parallel Wherefore the Axis of the Epicycle EDC will be carried alwayes parallel to it self which was to be proved Coroll From hence it is manifest that those two annual Motions which Copernicus ascribes to the Earth are reducible to this one Circular Simple Motion by which all the points of the moved Body are carried always with equal velocity that is in equal times they make equal revolutions uniformly This as it is the most simple so it is the most frequent of all Circular Motions being the same which is used by all men when they turn any thing round with their arms as they do in grinding or sifting For all the points of the thing moved describe lines which are like and equal to one another So that if a man had a Ruler in which many Pens points of equal length were fastned he might with this one Motion write many lines at once 3 Having shewed what Simple Motion is I will here also set down some properties of the same First when a Body is moved with Simple Motion in a fluid Medium which hath no vacuity it changes the situation of all the parts of the fluid ambient which resist its motion I say there are no parts so small of the fluid ambient how farre soever it be continued but do change their situation in such manner as that they leave their places continually to other small parts that come into the same For in the same second figure let any Body as KLMN be understood to be moved with Simple Circular Motion and let the Circle which every point thereof describes have any determined quantity suppose that of the same KLMN Wherefore the Center A and every other point and consequently the moved Body it self will be carried sometimes towards the side where is K and sometimes towards the other side where is M. When therefore it is carried to K the parts of the fluid Medium on that side will go back and supposing all space to be full others on the other side will succeed And so it will be when the Body is carried to the side M and to N and every way Now when the neerest parts of the fluid Medium go back it is necessary that the parts next to those neerest parts go back also and supposing still all space to be full other parts will come into their places with succession perpetual and infinite Wherefore all even the least parts of the fluid Medium change their places c. which was to be proved It is evident from hence that Simple Motion whether Circular or not Circular of Bodies which make perpetual returns to their former places hath greater or less force to dissipate the parts of resisting Bodies as it is more or less swift and as the lines described have greater or less magnitude Now the greatest Velocity that can be may be understood to be in the least circuit and the least in the greatest and may be so supposed when there is need 4 Secondly supposing the same Simple Motion in the Aire Water or other fluid Medium the parts of the Medium which adhere to the Moved Body will be carried about with the same Motion and Velocity so that in what time soever any point of the Movent finishes its Circle in the same time every part of the Medium which adheres to the Movent shall also describe such a part of its Circle as is equal to the whole Circle of the Movent I say it shall describe a part and not the whole Circle because all its parts receive their motion from an interiour concentrique Movent and of Concentrique Circles the exteriour are alwayes greater then the interiour nor can the motion imprinted by any Movent be of greater Velocity then that of the Movent it self From whence it follows that the more remote parts of the fluid ambient shall finish their Circles in times which have to one another the same proportion with their distances from the Movent For every point of the fluid ambient as long as it toucheth the Body which carries it about is carried about with it and would make the same Circle but that it is left behind so much as the exteriour Circle exceeds the interiour So that if we suppose some thing which is not fluid to float in that part of the fluid ambient which is neerest to the Movent it will together with the Movent be carried about Now that part of the fluid ambient which is not the neerest but almost the neerest receiving its degree of velocity from the neerest which degree cannot be greater then it was in the giver doth therefore in the same time make a Circular Line not a whole Circle yet equal to the whole Circle of the neerest Therefore in the same time that the Movent describes its Circle that which doth not touch it shall not describe its Circle yet it shall describe such a part of it as is equal to the whole Circle of the Movent And after the same manner the more remote parts of the ambient will describe in the same time such parts of their Circles as shall be severally equal to the whole Circle of the Movent and by consequent they shall finish their whole Circles in times proportional to their distances from the Movent which was to be proved 5 Thirdly The same Simple Motion of a Body placed in a fluid Medium congregates or gathers into one place such things as naturally float in that Medium if they be Homogeneous and if they be Heterogeneous it separates and dissipates them But if such things as be Heterogeneous do not float but settle then the same Motion stirs and mingles them disorderly together For seeing Bodies which are unlike to one another that is Heterogeneous Bodies are not unlike in that they are Bodies for Bodies as Bodies have no difference but onely from some special Cause that is from some internal Motion or Motions of their smallest parts for I have shewn in the 9th Chapter and 9th Article that all Mutation is such Motion it remains that Heterogeneous Bodies have their unlikeness or difference from one another from their internal or specifical Motions Now Bodies w ch have such difference receive unlike different Motions from the same external common Movent and therefore they will not be moved together that is to say they will be dissipated And being dissipated they will necessarily at some time or other meet with Bodies like themselves and be moved
nor can they go directly backwards against the force of the Movent it remayns therefore that they diffuse themselves upon the Superficies of that Body as towards O and P Which was to be proved 9 Compounded Circular Motion in which all the parts of the moved Body do at once describe Circumferences some greater others less according to the proportion of their several distances from the common Center carries about with it such Bodies as being not fluid adhere to the Body so moved and such as do not adhere it casteth forwards in a Straight Line which is a Tangent to the point from which they are cast off For let there be a Circle whose Radius is AB in the fourth figure and let a Body be placed in the Circumference in B which if it be fixed there will necessarily be carried about with it as is manifest of it self But whilest the motion proceeds let us suppose that Body to be unfixed in B. I say the Body wil cōtinue its motion in the Tangent BC. For let both the Radius AB and the Sphere B be conceived to consist of hard matter and let us suppose the Radius AB to be stricken in the point B by some other Body which falls upon it in the Tangent DB. Now therefore there will be a motion made by the concourse of two things the one Endeavour towards C in the Straight Line DB produced in which the Body B would proceed if it were not retained by the Radius AB the other the Retention it self But the Retention alone causeth no endeavour towards the Center and therefore the Retention being taken away which is done by the unfixing of B there will remain but one Endeavour in B namely that in the Tangent BC. Wherefore the Motion of the Body B unfixed will proceed in the Tangent BC which was to be proved By this demonstration it is manifest that Circular Motion about an unmoved Axis shakes off and puts further from the Center of its motion such things as touch but do not stick fast to its Superficies and the more by how much the distance is greater from the Poles of the Circular Motion and so much the more also by how much the things that are shaken off are less driven towards the Center by the fluid ambient for other Causes 10 If in a fluid Medium a Spherical Body be moved with simple Circular Motion and in the same Medium there float another Sphere whose matter is not fluid this Sphere also shall be moved with simple Circular Motion Let BCD in the 5th figure be a Circle whose Center is A and in whose Circumference there is a Sphere so moved that it describes with Simple Motion the Perimeter BCD Let also EFG be another Sphere of Consistent matter whose Semidiameter is EH and Center H and with the Radius AH let the Circle HI be described I say the Sphere EFG will by the Motion of the Body in BCD be moved in the Circumference HI with Simple Motion For seeing the Motion in BCD by the 4th Article of this Chapter makes all the points of the fluid Medium describe in the same time Circular Lines equal to one another the points E H and G of the Straight Line EHG will in the same time describe with equal Radii equal Circles Let EB be drawn equal and parallel to the Straight Line AH and let AB be connected which will therefore be equal and parallel to EH and therefore also if upon the Center B and Radius BE the arch EK be drawn equal to the arch HI and the straight Lines AI BK and IK be drawn BK and AI will be equal and they will also be parallel because the two arches EK and HI that is the two angles KBE and IAH are equal and consequently the Straight Lines AB and KI which connect them will also be equal and parallel Wherefore KI and EH are parallel Seeing therefore E and H are carried in the same time to K and I the whole Straight Line IK will be parallel to EH from whence it departed And therefore seeing the Sphere EFG is supposed to be of consistent matter so as all its points keep alwayes the same situation it is necessary that every other Straight Line taken in the same Sphere be carried alwayes parallel to the places in which it formerly was Wherefore the Sphere EFG is moved with simple Circular Motion which was to be demonstrated 11 If in a fluid Medium whose parts are stirred by a Body moved with Simple Motion there float annother Body which hath its Superficies either wholly hard or wholly fluid the parts of this Body shall approach the Center equally on all sides that is to say the motion of the Body shall be Circular and Concentrique with the motion of the Movent But if it have one side hard and the other side fluid then both those Motions shall not have the same center nor shall the floating Body be moved in the Circumference of a perfect Circle Let a Body be moved in the Circumference of the Circle KL MN in the 2d figure whose center is A. And let there be another Body at I whose Superficies is either all hard or all fluid Also let the Medium in which both the Bodies are placed be fluid I say the Body at I will be moved in the Circle IB about the Center A. For this has been demonstrated in the last Article Wherefore let the Superficies of the Body at I be fluid on one side and hard on the other And first let the fluid side be towards the Center Seeing therefore the Motion of the Medium is such as that its parts do continually change their places as hath been shewn in the 5th Article if this change of place be considered in those parts of the Medium which are contiguous to the fluid Superficies it must needs be that the small parts of that Superficies enter into the places of the small parts of the Medium which are contiguous to them And the like change of place will be made with the next contiguous parts towards A. And if the fluid parts of the Body at I have any degree at all of tenacity for there are degrees of tenacity as in the Aire and Water the whole fluid side will be lifted up a little but so much the less as its parts have less tenacity whereas the hard part of the Superficies which is contiguous to the fluid part has no cause at all of elevation that is to say no endeavour towards A. Secondly let the hard Superficies of the Body at I be towards A. By reason therefore of the said change of place of the parts which are contiguous to it the hard Superficies must of necessity seeing by Supposition there is no empty Space either come neerer to A or else its smallest parts must supply the contiguous places of the Medium which otherwise would be empty But this cannot be by reason of
been shewn at the end of the 3d Article of the 15th Chapter The Cause therefore of their Restitution is some motion either of the parts of the Ambient or of the parts of the Body compressed or extended But the parts of the Ambient have no endeavour which contributes to their Compression or Extension nor to the setting of them at liberty or Restitution It remayns therefore that from the time of their Compression or Extension there be left some endeavour or motion by which the impediment being removed every part resumes its former place that is to say the whole Restores it self 14 In the Carriage of Bodies if that Body which carries another hit upon any obstacle or be by any means suddenly stopped and that which is carried be not stopped it will go on till its motion be by some external impediment taken away For I have demonstrated in the 8th Chapter at the 19th Article that Motion unless it be hindred by some external resistance will be continued eternally with the same celerity and in the 7th Article of the 9th Chap. that the action of an external Agent is of no effect without contact When therefore that which carrieth another thing is stopped that stop doth not presently take away the motion of that which is carried It will therefore proceed till its motion be by little and little extinguished by some external resistance Which was to be proved Though experience alone had been sufficient to prove this In like manner if that Body which carrieth another be put from rest into sudden motion that which is carried will not be moved forwards together with it but will be left behind For the contiguous part of the Body carried hath almost the same motion with the Body which carries it and the remote parts will receive different Velocities according to their different distances from the Body that carries them namely the more remote the parts are the less will be their degrees of Velocity It is necessary therefore that the Body which is carried be left accordingly more or less behind And this also is manifest by experience when at the starting forward of the Horse the Rider falleth backwards 15 In Percussion therefore when one hard Body is in some small â—art of it stricken by another with great force it is not necessary that the whole Body should yeild to the stroke with the same celerity with which the stricken part yeilds For the rest of the parts receive their motion from the motion of the part stricken and yeilding which motion is less propagated every way towards the sides then it is directly forwards And hence it is that sometimes very hard Bodies which being erected can hardly be made to stand are more easily broken then thrown down by a violent stroke when nevertheless if all their parts together were by any weak motion thrust forwards they would easily be cast down 16 Though the difference between Trusion and Percussion consist onely in this that in Trusion the motion both of the Movent and Moved Body begin both together in their very contact and in Percussion the striking Body is first moved and afterwards the Body stricken Yet their Effects are so different that it seems scarce possible to compare their forces with one another I say any effect of Percussion being propounded as for example the stroke of a Beetle of any weight assigned by which a Pile of any given length is to be driven into earth of any tenacity given it seems to me very hard if not impossible to define with what weight or with what stroke and in what time the same pile may be driven 〈◊〉 a depth assigned into the same earth The cause of which difficulty is this that the velocity of the Percutient is to be compared with the magnitude of the Ponderant Now Velocity seeing it is computed by the length of space transmitted is to be accounted but as one Dimension but Waight is as a solid thing being measured by the dimension of the whole Body And there is no comparison to be made of a Solid Body with a Length that is with a Line 17 If the internal parts of a Body be at rest or retain the same situation with one another for any time how little soever there cannot in those parts be generated any new motion or endeavour whereof the efficient cause is not without the Body of which they are parts For if any small part which is comprehended within the Superficies of the whole Body be supposed to be now at rest and by and by to be moved that part must of necessity receive its motion from some moved and contiguous Body But by supposition there is no such moved and contiguous part within the Body Wherefore if there be any Endeavour or Motion or change of situation in the internal parts of that Body it must needs arise from some efficient cause that is without the Body which contains them Which was to be proved 18 In hard Bodies therefore which are compressed or extended if that which compresseth or extendeth them being taken away they restore themselves to their former place or situation it must needs be that that Endeavour or Motion of their internal parts by which they were able to recover their former places or situations was not extinguished when the force by which they were compressed or extended was taken away Therefore when the Lath of a Cross-bow bent doth as soon as it is at liberty restore it self though to him that judges by Sense both it and all its parts seem to be at rest yet he that judging by Reason doth not account the taking away of impediment for an efficient cause nor conceives that without an efficient cause any thing can pass from Rest to Motion will conclude that the parts were already in motion before they began to restore themselves 19 Action and Reaction proceed in the same Line but from opposite Terms For seeing Reaction is nothing but Endeavour in the Patient to restore it self to that situation from which it was forced by the Agent the endeavour or motion both of the Agent and Patient or Reagent will be propagated between the same terms yet so as that in Action the Term from which is in Reaction the Term to which And seeing all Action proceeds in this manner not onely between the opposite Terms of the whole line in which it is propagated but also in all the parts of that line the Terms from which and to which both of the Action and Reaction will be in the same line Wherefore Action and Reaction proceed in the same line c. 20 To what has been said of Motion I will add what I have to say concerning Habit. Habit therefore is a generation of Motion not of Motion simply but an easie conducting of the moved Body in a certain and designed way And seeing it is attained by the weakning of such endeavours as divert its motion therefore such endeavours are to be
that which the Line of Incidence makes with that Line which from the point of Refraction is drawn perpendicular to the separating Superficies 8 The Angle of Incidence is the Complement to a right Angle of the Angle of Inclination And so in the first Figure the Refraction is made in A B F. The Refracted Line is B F. The Line of Incidence is A B. The Point of Incidence and of Refraction is B. The Refracting or Separating Superficies is D B E. The Line of Incidence produced directly is A B C The Perpendicular to the separating Superficies is B H. The Angle of Refraction is C B F. The Angle Refracted is H B F. The Angle of Inclination is A B G or H B C. The Angle of Incidence is A B D. 9 Moreover the Thinner Medium is understood to be that in which there is less resistance to Motion or to the generation of Motion the Thicker that wherin there is greater resistance 10 And that Medium in which there is equal resistance every where is a Homogeneous Medium All other Mediums are Heterogeneous 2 If a Body pass or there be generation of Motion from one Medium to another of different Density in a line perpendicular to the Separating Superficies there will be no Refraction For seeing on every side of the perdendicular all things in the Mediums are supposed to be like and equal if the Motion it self be supposed to be perpendicular the Inclinations also will be equal or rather none at all and therefore there can be no cause from which Refraction may be inferred to be on one side of the perpendicular which wil not cōclude the same Refraction to be on the other side Which being so Refraction on one side will destroy Refraction on the other side and consequently either the Refracted line will be every where which is absurd or there will be no Refracted line at all which was to be demonstrated Corol. It is manifest from hence that the cause of Refraction consisteth onely in the obliquity of the line of Incidence whether the Incident Body penetrate both the Mediums or without penetrating propagate motion by Pressure onely 3 If a Body without any change of situation of its internal parts as a stone be moved obliquely out of the thinner Medium and proceed penetrating the thicker Medium and the thicker Medium be such as that its internal parts being moved restore themselves to their former situation the angle Refracted will be greater then the angle of Inclination For let D B E in the same first figure be the separating Superficies of two Mediums and let a Body as a stone thrown be understood to be moved as is supposed in the straight line A B C and let A B be in the thinner Medium as in the Aire and B C in the thicker as in the Water I say the stone w ch being thrown is moved in the line A B will not proceed in the line B C but in some other line namely that with which the perpendicular B H makes the Refracted angle H B F greater then the angle of Inclination H B C. For seeing the stone coming from A and falling upon B makes that which is at B proceed towards H and that the like is done in all the straight lines which are parallel to B H and seeing the parts moved restore themselves by contrary motion in the same line there will be contrary motion generated in H B and in all the straight lines which are parallel to it Wherefore the motion of the stone will be made by the concourse of the motions in A G that is in D B and in G B that is in B H and lastly in H B that is by the concourse of three motions But by the concourse of the motions in A G and B H the stone will be carried to C and therefore by adding the motion in H B it will be carried higher in some other line as in B F and make the angle H B F greater then the angle H B C. And from hence may be derived the cause why Bodies which are thrown in a very oblique line if either they be any thing flat or be thrown with great force will when they fall upon the water be cast up again from the water into the aire For let A B in the 2d figure be the superficies of the water into which from the point C let a stone be thrown in the straight line C A making with the line B A produced a very little angle C A D and producing B A indefinitely to D let C D be drawn perpendicular to it and A E parallel to C D. The stone therefore will be moved in C A by the concourse of two motions in C D and D A whose velocities are as the lines themselves C D and D A. And from the motion in C D and all its parallels downwards as soon as the stone falls upon A there will be Reaction upwards because the water restores it self to its former situation If now the stone be thrown with sufficient obliquity that is if the straight line C D be short enough that is if the endeavour of the stone downwards be less then the Reaction of the water upwards that is less then the endeavour it hath from its own gravity for that may be the stone will by reason of the excess of the endeavour which the water hath to restore it self above that which the stone hath downwards be raised again above the Superficies A B and be carried higher being reflected in a line which goes higher as the line A G. 4 If from a point whatsoever the Medium be Endeavour be propagated every way into all the parts of that Medium and to the same Endeavour there be obliquely opposed another Medium of a different nature that is either thinner or thicker that Endeavour will be so refracted that the sine of the angle Refracted to the sine of the angle of Inclination will be as the density of the first Medium to the density of the second Medium reciprocally taken First let a Body be in the thinner Medium in A Figure 3d. and let it be understood to have endeavour every way and consequently that its endeavour proceed in the lines A B and A b to which let B b the superficies of the thicker Medium be obliquely opposed in B and b so that A B and A b be equal and let the straight line B b be produced both wayes From the points B and b let the perpendiculars B C and b c be drawn and upon the centers B and b and at the equal distances B A and b A let the Circles A C and A c be described cutting B C and b c in C and c and the same C B and c b produced in D and d as also A B and A b produced in E and e. Then from the point A to the straight lines B C and b c let the perpendiculars
by true Ratiocination from knowledge first had of their Causes and Generation and of such Causes or Generations as may be from former knowledge of their Effects or Appearances There are therefore two Methods of Philosophy One from the Generation of things to their possible Effects and the other from their Effects or Appearances to some possible Generation of the same In the former of these the Truth of the first Principles of our ratiocination namely Definitions is made and constituted by our selves whilest we consent and agree about the Appellations of things And this part I have finished in the foregoing Chapters in which if I am not deceived I have affirmed nothing saving the Definitions themselves which hath not good coherence with the Definitions I have given that is to say which is not sufficiently demonstrated to all those that agree with me in the use of Words and Appellations for whose sake onely I have written the same I now enter upon the other part which is the finding out by the Appearances or Effects of Nature which we know by Sense some wayes and means by which they may be I do not say they are generated The Principles therefore upon which the following discourse depends are not such as we our selves make and pronounce in general terms as Definitions but such as being placed in the things themselves by the Authour of Nature are by us observed in them and we make use of them in single and particular not universal propositions Nor do they impose upon us any necessity of constituting Theoremes their use being onely though not without such general Propositions as have been already demonstrated to shew us the possibility of some production or generation Seeing therefore the Science which is here taught hath its Principles in the Appearances of Nature and endeth in the attayning of some knowledge of Natural causes I have given to this Part the title of PHYSIQUES or the PHAENOMENA of NATURE Now such things as appear or are shewn to us by Nature we call Phaenomena or Appearances Of all the Phaenomena or Appearances which are neer us the most admirable is Apparition it self 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 namely that some Natural Bodies have in themselves the patterns almost of all things and others of none at all So that if the Appearances be the Principles by which we know all other things we must needs acknowledge Sense to be the Principle by which we know those Principles that all the knowledge we have is derived from it And as for the causes of Sense we cannot begin our search of them from any other Phaenomenon then that of Sense it self But you will say by what Sense shall we take notice of Sense I answer by Sense it self namely by the Memory which for some time remains in us of things sensible though they themselves pass away For he that perceiues that he hath perceived remembers In the first place therefore the causes of our Perception that is the causes of those Ideas and Phantasmes which are perpetually generated within us whilest we make use of our Senses are to be enquired into and in what manner their generation proceeds To help which Inquisition we may observe first of all that our Phantasmes or Ideas are not alwayes the same but that new ones appear to us and old ones vanish according as we apply our Organs of Sense now to one Object now to another Wherefore they are generated and perish And from hence it is manifest that they are some change or mutation in the Sentient 2 Now that all Mutation or Alteration is Motion or Endeavour and Endeavour also is Motion in the internal parts of the thing that is altered hath been proved in the 9th Article of the 8th Chapter from this that whilest even the least parts of any Body remain in the same situation in respect of one another it cannot be said that any alteration unless perhaps that the whole Body together hath been moved hath hapned to it but that it both appeareth and is the same it appeared was before Sense therefore in the Sentient can be nothing else but motion in some of the internal parts of the Sentient and the parts so moved are parts of the Organs of Sense For the parts of our Body by which we perceive any thing are those we commonly call the Organs of Sense And so we find what is the Subject of our Sense namely that in which are the Phantasmes and partly also we have discovered the nature of Sense namely that it is some internal Motion in the Sentient I have shewn besides in the 8th Chap. at the 7th Article that no Motion is generated but by a Body contiguous and Moved From whence it is manifest that the immediate cause of Sense or Perception consists in this that the first Organ of Sense is touched and pressed For when the uttermost part of the Organ is pressed it no sooner yeilds but the part next within it is pressed also and in this manner the pressure or Motion is propagated through all the parts of the Organ to the innermost And thus also the pressure of the uttermost part proceeds from the pressure of some more remote Body and so continually till we come to that from which as from its fountain we derive the Phantasme or Idea that is made in us by our Sense And this whatsoever it be is that we commonly call the Object Sense therefore is some internal Motion in the Sentient generated by some internal Motion of the parts of the Object and propagated through all the Media to the innermost part of the Organ By which words I have almost defined what Sense is Moreover I have shewn in the 2d Article of the 15 Chapter that all Resistance is Endeavour opposite to another Endeavour that is to say Reaction Seeing therefore there is in the whole Organ by reason of its own internal natural Motion some Resistance or Reaction against the Motion which is propagated from the Object to the innermost part of the Organ there is also in the same Organ an Endeavour opposite to the Endeavour which proceeds from the Object so that when that Endeavour inwards is the last action in the act of Sense then from the Reaction how little soever the duration of it be a Phantasme or Idea hath its being which by reason the Endeavour is now outwards doth alwayes appear as something situate without the Organ So that now I shall give you the whole Definition of Sense as it is drawn from the explication of the causes thereof and the order of its generation thus SENSE is a Phantasme made by the Reaction and endeavour outwards in the Organ of Sense caused by an Endeavour inwards from the Object remayning for some time more or less 3 The Subject of Sense is the Sentient it self namely some living Creature and we speak more correctly when we say a Living Creature seeth then when we say the Eye seeth The Object is
to it self so that in what part soever of the Ecliptick the Center of the Epicycle be found and in what part soever of the Epicycle the Center of the Earth be found at the same time the Axis of the Earth will be parallel to the place where the same Axis would have been if the Center of the Earth had never gone out of the Ecliptick Now as I have demonstrated the simple annual motion of the Earth from the supposition of Simple Motion in the Sunne so from the supposition of Simple Motion in the Earth may be demonstrated the monethly Simple Motion of the Moon For if the names be but changed the Demonstration will be the same and therefore need not be repeated 7 That which makes this supposition of the Sunnes Simple Motion in the Epicycle fghi probable is First that the Periods of all the Planets are not onely described about the Sunne but so described as that they are al contained within the Zodiack that is to say within the latitude of about 16 degrees for the cause of this seems to depend upon some power in the Sunne especially in that part of the Sunne which respects the Zodiack Secondly that in the whole coâ—passe of the heavens there appears no other Body from which the cause of this Phaenomenon can in probability be derived Besides I could not imagine that so many and such various motions of the Planets should have no dependance at all upon one another But by supposing motive power in the Sunne we suppose motion also for power to move without motion is no power at all I have therefore supposed that there is in the Sunne for the governing of the primary Planets and in the Earth for the governing of the Moon such motion as being received by the primary Planets and by the Moon makes them necessarily appear to us in such manner as we see them Whereas that circular motion which is commonly attributed to them about a fixed Axis which is called Conversion being a motion of their parts onely and not of their whole Bodies is insufficient to salve their Appearances For seeing whatsoever is so moved hath no endeavour at all towards those parts which are without the circle they have no power to propagate any endeavour to such Bodies as are placed without it And as for them that suppose this may be done by Magnetical Virtue or by incorporeall and immateriall Species they suppose no naturall cause nay no cause at all For there is no such thing as an Incorporeal Movent and Magnetical Virtue is a thing altogether unknown and whensoever it shall be known it will be found to be a motion of Body It remaines therefore that if the primary Planets be carried about by the Sunne and the Moon by the Earth they have the simple circular motions of the Sunne and the Earth for the causes of their circulations Otherwise if they be not carried about by the Sunne and the Earth but that every Planet hath been moved as it is now moved ever since it was made there will be of their motions no cause naturall For either these motions were concreated with their Bodies and their cause is supernatural or they are coeternal with them and so they have no cause at all For whatsoever is Eternall was never generated I may add besides to confirme the probability of this simple motion that allmost all learned men are now of the same opinion with Copernicus concerning the parallelisme of the Axis of the Earth it seemed to me to be more agreeable to truth or at least more handsome that it should be caused by simple Circular Motion alone than by two motions one in the Ecliptick and the other about the Earths own Axis the contrary way neither of them Simple nor either of them such as might be produced by any motion of the Sunne I thought best therefore to retain this Hypothesis of Simple Motion and from it to derive the causes of as many of the Phaenomena as I could and to let such alone as I could not deduce frm thence It will perhaps be objected that although by this supposition the reason may be given of the Parallelisme of the Axis of the Earth and of many other Appearances nevertheless seeing it is done by placing the Body of the Sunne in the Center of that Orbe which the Earth describes with its annual motion the supposition it self is false because this annual Orbe is excentrique to the Sunne In the first place therefore let us examine what that Excentricity is and whence it proceeds 8 Let the annual Circle of the Earth abcd in the same 3d figure be divided into four equal parts by the straight lines ac bd cutting one another in the Center e and let a be the beginning of Libra b of Capricorn c of Aries and d of Cancer and let the whole Orbe abcd be understood according to Copernicus to have every way so great distance from the Zodiack of the fixed Starres that it be in comparison with it but as a point Let the Earth be now supposed to be in the beginning of Libra at a. The Sunne therefore will appear in the beginning of Aries at c. Wherefore if the Earth be moved from a to b the apparent motion of the Sunne will be from c to the beginning of Cancer in d and the Earth being moved forwards from b to c the Sunne also will appear to be moved forwards to the beginning of Libra in a Wherefore cda will be the Summer Arch and the Winter Arch will be abc Now in the time of the Suns apparent motion in the Summer Arch there are numbred 186¾ dayes and consequently the Earth makes in the same time the same number of diurnal conversions in the Arch abc and therefore the Earth in its motion through the Arch cda will make onely 178½ diurnal conversions Wherefore the Arch a b c ought to be greater then the Arch c d a by 8¼ dayes that is to say by almost so many degrees Let the Arch a r as also c s be each of them an Arch of two degrees and 1 16. Wherefore the Arch r b s will be greater then the Semicircle a b c by 4 degrees and â…› and greater then the Arch s d r by 8 degrees and ¼ The Equinoxes therefore will be in the points r s and therefore also when the Earth is in r the Sunne will appear in s. Wherefore the true place of the Sunne will be in t that is to say without the Center of the Earths annual motion by the quantity of the Sine of the Arch a r or the Sine of two degrees and 16 minutes Now this Sine putting 100000 for the Radius will be neer 3580 parts thereof And so munh is the Excentricity of the Earths annual motion provided that that motion be in a perfect circle and s r are the Equinoctial points and the straight lines s r c a produced both wayes till they
the midst of the Heaven 15 The cause of Whiteness 16 The cause of Blackness 1 BEsides the Starres of which I have spoken in the last Chapt. whatsoever other Bodies there be in the World they may be all comprehended under the name of Intersidereal Bodies And these I have already supposed to be either the most fluid Aether or such Bodies whose parts have some degree of cohaesion Now these differ from one another in their several Consistencies Magnitudes Motions and Figures In Consistency I suppose some Bodies to be Harder others Softer through all the several degrees of Tenacity In Magnitude some to be Greater others Less and many unspeakably Little For we must remember that by the Understanding Quantity is divisible into divisibles perpetually And therefore if a man could do as much with his hands as he can with his Understanding he would be able to take from any given magnitude a part which should be less then any other magnitude given But the Omnipotent Creator of the World can actually from a part of any thing take another parâ— as farre as we by our Understanding can conceive the same to be divisible Wherefore there is no impossible Smalness of Bodies And what hinders but that we may think this likely For we know there are some living Creatures so small that we can scarce see their whole Bodies Yet even these have their young ones their little Veins and other Vessels and their Eyes so smal as that no Microscope can make them visible So that we cannot suppose any magnitude so little but that our very supposition is actually exceeded by Nature Besides there are now such Microscopes commonly made that the things we see with them appear a hundred thousand times bigger then they would do if we looked upon them with our bare Eyes Nor is there any doubt but that by augmenting the power of these Microscopes for it may be augmented as long as neither Matter nor the hands of Workmen are wanting every one of those hundred thousandth parts might yet appear a hundred thousand times geater then they did before Neither is the Smalness of some Bodies to be more admired then the vast Greatness of others For it belongs to the same infinite Power as well to augment infinitely as infinitely to diminish To make the great Orbe namely that whose Radius reacheth from the Earth to the Sunne but as a point in respect of the distance between the Sunne and the fixed Starres and on the contrary to make a Body so little as to be in the same proportion less then any other visible Body proceeds equally from one and the same Authour of Nature But this of the immense distance of the fixed Starres which for a long time was accounted an incredible thing is now believed by almost all the Learned Why then should not that other of the smalness of some Bodies become credible at some time or other For the Majesty of God appears no less in small things then in great and as it exceedeth humane sense in the immense greatness of the Universe so also it doth in the smalness of the parts thereof Nor are the first Elements of Compositions nor the first Beginnings of Actions nor the first Moments of Times more credible then that which is now believed of the vast distance of the fixed Starres Some things are acknowledged by mortal men to be very Great though Finite as seeing them to be such They acknowledge also that some things which they do not see may be of infinite magnitude But they are not presently nor without great study perswaded that there is any Mean between Infinite the Greatest of those things which either they see or imagine Nevertheless when after meditation contemplation many things which we wondred at before are now grown more familiar to us we then believe them and transferre our admiration from the Creatures to the Creator But how little soever some Bodies may be yet I will not suppose their quantity to be less then is requisite for the salving of the Phaenomena And in like manner I shall suppose their motion namely their Velocity and Slowness and the Variety of their Figures to be onely such as the explication of their natural causes requires And lastly I suppose that the parts of the pure Aether as if it were the First Matter have no motion at all but what they receive from Bodies which float in them and are not themselves fluid 2 Having laid these Grounds let us come to speake of Causes and in the first place let us inquire what may be the cause of the Light of the Sunne Seeing therefore the Body of the Sunne doth by its simple circular motion thrust away the ambient aethereall substance sometimes one way sometimes another so that those parts which are next the Sunne being moved by it doe propagate that motion to the next remote parts and these to the next and so on continually it must needs be that notwithstanding any distance the foremost part of the Eie will at last be pressed and by the pressure of that part the motion will be propagated to the innermost part of the Organ of Sight namely to the Heart and from the reaction of the Heart there will proceed an endeavour back by the same way ending in the endeavour outwards of the Coat of the Eie called the Retina But this endeavour outwards as has been defined in the 25 chapter is the thing which is called Light or the Phantasme of a Lucid Body For it is by reason of this Phantasme that an Object is called Lucid. Wherefore we have a possible cause of the Light of the Sunne which I undertook to find 3 The generation of the Light of the Sunne is accompanied with the generation of Heat Now every man knowes what Heat is in himselfe by feeling it when he growes Hot but what it is in other things he knowes onely by ratiocination For it is one thing to grow Hot and another thing to Heat or make Hot. And therefore though we perceive that the Fire or the Sunne Heateth yet we doe not perceive that it is it selfe Hot. That other living creatures whilest they make other things Hot are Hot themselves we inferre by reasoning from the like sense in our selves But this is not a necessary inference For though it may truly be said of living Creatures that They Heat therefore they are themselves Hot yet it cannot from hence be truly inferred that Fire Heateth therefore it is it selfe Hot no more then this Fire causeth Pain therefore it is it self in Pain Wherefore that is onely and properly called Hot which when we feel we are necessarily Hot. Now when we grow Hot we find that our Spirits and Blood and whatsoever is fluid within us is called out from the internall to the externall parts of our Bodies more or lesse according to the degree of the Heat and that our Skin swelleth He therefore that can give a possible cause
of this Evocation and Swelling and such as agreeth with the rest of the Phaenomena of Heat may be thought to have given the cause of the Heat of the Sunne It hath been shewn in the 5 article of the 21 chapter that the fluid Medium which we call the Aire is so moved by the simple circular motion of the Sunne as that all its parts even the least do perpetually change places with one another which change of places is that which there I called Fermentation From this Fermentation of the Aire I have in the 8 article of the last chapter demonstrated that the water may be drawn up into the clouds And I shall now shew that the fluid parts may in like manner by the same Fermentation be drawn out from the internall to the externall parts of our Bodies For seeing that wheresoever the fluid Medium is contiguous to the Body of any living creature there the parts of that Medium are by perpetuall change of place separated from one another the contiguous parts of the living creature must of necessity endeavour to enter into the spaces of the separated parts For otherwise those parts supposing there is no Vacuum would have no place to go into And therefore that which is most fluid and separable in the parts of the living creature which are contiguous to the Medium will go first out and into the place thereof will succeed such other parts as can most easily transpire through the poâ—es of the skin And from hence it is necessary that the rest of the parts which are not separated must all together be moved outwards for the keeping of all places full But this motion outwards of all parts together must of necessity press those parts of the ambient Aire which are ready to leave their places and therefore all the parts of the Body endeavouring at once that way makes the Body swell Wherefore a possible cause is given of Heat from the Sunne which was to be done 4 We have now seen how Light and Heat are generated Heat by the simple motion of the Medium making the parts perpetually change places with one another and Light by this that by the same simple motion Action is propagated in a straight line But when a Body hath its parts so moved that it sensibly both Heats and Shines at the same time then it is that we say Fire is generated Now by Fire I do not understand a Body distinct from matter combustible or glowing as Wood or Iron but the matter it self not simply and always but then onely when it shineth and heateth He therefore that renders a cause possible and agreeable to the rest of the Phaenomena namely whence and from what action both the Shining and Heating proceed may be thought to have given a possible cause of the generation of Fire Let therefore ABC in the first Figure be a Sphere or the portion of a Sphere whose Center is D and let it be transparent and homogeneous as Cristal Glass or Water and objected to the Sunne Wherefore the foremost part ABC will by the simple motion of the Sunne by which it thrusts forwards the Medium be wrought upon by the Sun-beams in the straight lines EA FB and GC which straight lines may in respect of the great distance of the Sunne be taken for parallels And seeing the Medium within the Sphere is thicker then the Medium without it those Beams will be refracted towards their perpendiculars Let the straight lines EA and GC be produced till they cut the Sphere in H and I and drawing the perpendiculars AD and CD the refracted Beams EA and GC will of necessity fall the one between AH and AD the other between CI and CD Let those refracted Beams be AK and CL. And again let the lines DKM DLN be drawn perâ—endicular to the Sphere and let AK and CL be produced till they meet with the straight line BD produced in O. Seeing therefore the Medium within the Sphere is thicker then that without it the refracted line AK will recede further from the perpendicular KM then KO will recede from the same Wherefore KO will fall between the refracted line and the perpendicular Let therefore the refracted line be KP cutting FO in P and for the same reason the straight line LP will be the refracted line of the straight line CL. Wherfore seeing the Beams are nothing else but the Wayes in which the motion is propagated the motion about P will be so much more vehement then the motion about ABC by how much the base of the portion ABC is greater then the base of a like portion in the Sphere whose Center is P and whose magnitude is equal to that of the little Circle about P which comprehendeth all the Beams that are propagated from ABC and this Sphere being much less then the Sphere ABC the parts of the Medium that is of the Aire about P will change places with one another with much greater celerity then those about ABC If therefore any matter Combustible that is to say such as may be easily dissipated be placed in P the parts of that matter if the proportion be great enough between AC and a like portion of the little circle about P wil be freed from their mutual cohaesion and being separated will acquire simple motion But vehement simple motion generates in the beholder a Phantasm of Lucid and Hot as I have before deâ—onstrated of the simple motion of the Sunne and therefore the combustible matter which is placed in P will be made Lucid and Hot that is to say will be Fire Wherefore I have rendered a possible cause of Fire which was to be done 5 From the manner by which the Sunne generateth Fire it is easy to explaine the manner by which Fire may be generated by the collision of two Flints For by that Collision some of those particles of which the stone is compacted are violently separated and thrown off and being withall swiftly turned round the Eie is moved by them as it is in the generation of Light by the Sunne Wherefore they shine and falling upon matter which is already halfe dissipated such as is Tinder they throughly dissipate the parts thereof and make them turn round From whence as I have newly shewn Light and Heat that is to say Fire is generated 6 The shining of Glow-worms some kinds of Rotten Wood and of a kinde of stone made at Bolognia may have one common cause namely the exposing of them to the hot Sunne We finde by experience that the Bolonian stone shines not unless it be so exposed and after it has been exposed it shines but for a little time namely as long as it retains a certain degree of heat And the cause may be that the parts of which it is made may together with heat have Simple Motion imprinted in them by the Sunne Which if it be so it is necessary that it shine in the dark as
long as there is sufficient heat in it but this ceasing it will shine no longer Also we find by experience that in the Glow-worm there is a certain thick humour like the Cristalline humour of the Eie which if it be taken out and held long enough in ones fingers and then be carried into the dark it will shine by reason of the warmth it received from the fingers but as soon as it is cold it will cease shining From whence therefore can these creatures have their Light but from lying all day in the Sun-shine in the hottest time of Summer In the same manner Rotten Wood except it grow rotten in the Sun-shine or be afterwards long enough exposed to the Sunne will not shine That this doth not happen in every Worm nor in all kinds of Rotten Wood nor in all Calcined Stones the cause may be that the parts of which those Bodies are made are different both in motion and figure from the parts of Bodies of other kinds 7 Also the Sea-water shineth when it is either dashed with the strokes of Oares or when a Ship in its course breaks strongly through it but more or less according as the Winde blows from different points The cause whereof may be this that the particles of salt though they never shine in the Salt-pits where they are but slowly drawn up by the Sunne being here beaten up into the aire in greater quantities and with more force are withall made to turn round and consequently to shine though weakly I have therefore given a possible cause of this Phaenomenon 8 If such matter as is compounded of hard little Bodies be set on fire it must needs be that as they flye out in greater or lesse quantities the Flame which is made by them will be greater or less And if the aethereal or fluid part of that matter fly out together with them their motion will be the Swifter as it is in Wood and other things which flame with a manifest mixture of Winde When therefore these hard particles by their flying out move the Eye strongly they shine bright and a great quantity of them flying out together they make a great shining Body For Flame being nothing but an aggregate of shining particles the greater the aggregate is the greater and more manifest will be the Flame I have therefore shewn a possible cause of Flame And from hence the cause appears evidently why Glass is so easily and quickly melted by the small Flame of a candle blown which will not be melted without blowing but by a very strong Fire Now if from the same matter there be a part broken off namely such a part as consisteth of many of the small particles of this is made a Spark For from the breaking off it hath a violent turning round and from hence it shines But though from this matter there fly neither Flame nor Sparks yet some of the smallest parts of it may be carried out as farre as to the Superficies and remain there as Ashes the parts whereof are so extremely small that it cannot any longer be doubted how farre Nature may proceed in Dividing Lastly though by the application of fire to this matter there fly little or nothing from it yet there will be in the parts an endeavour to Simple motion by which the whole Body will either be Melted or which is a degree of Melting Softned For all Motion has some effect upon all Matter whatsoever as has been shewn at the 3d Article of the 16th Chapter Now if it be softned to such a degree as that the stubborness of the parts be exceeded by their gravity then we say it is Melted otherwise Softned and made Pliant and Ductile Again the matter having in it some particles hard others aethereal or watery if by the application of fire these later be called out the former will thereby come to a more full contact with one another and consequently will not be so easily separated that is to say the whole Body will be made Harder And this may be the cause why the same Fire makes some things Soft others Hard. 9 It is known by experience that if Hay be laid wet together in a heap it will after a time begin to smoke and then burn as it were of it self The cause whereof seems to be this that in the Aire which is enclosed within the Hay there are those little Bodies which as I have supposed are moved freely with simple Motion But this Motion being by degrees hindred more and more by the descending moisture which at the last fils and stops all the passages the thinner parts of the Aire ascend by penetrating the water and those hard little Bodâ—â— being so thrust together that they touch and press one another acquire stronger motion till at last by the increased strength of this motion the watery parts are first driven outwards from whence appears Vapour and by the continued increase of this motion the smallest particles of the dryed Hay are forced out and recovering their natural simple Motion they grow Hot and Shine that is to say they are set on Fire The same also may be the cause of Lightning which happens in the hottest time of the yeare when the water is raised up in greatest quantity and carried highest For after the first Clouds are raised others after others follow them and being congeled above they happen whilest some of them ascend and others descend to fall upon another in such manner as that in some places all their parts are joyned together in others they leave hollow Spaces between them aud into these spaces the aethereall parts being forced out by the compressure of the Clouds many of the harder little Bodies are so pent together as that they have not the liberty of such motion as is naturall to the Aire Wherefore their endeavour growes more vehement till at last they force their way through the Clouds sometimes in one place sometimes in another and breaking through with great noise they move the aire violently striking our Eies generate Light that is to say they Shine And this Shining is that we call Lightning 10 The most common Phaenomenon proceeding from Fire and yet the most admirable of all others is the force of Gunpowder fired which being compounded of Niter Brimstone and Coles beaten small hath from the Coles its first taking fire from the Brimstone its nourishment and flame that is to say Light and motion and from the Niter the vehemence of both Now if a piece of Niter before it is beaten be laid upon a burning Cole first it melts and like water quencheth that part of the Cole it toucheth Then Vapor or Aire flying out where the Cole and Niter joyne bloweth the Cole with great swiftnesse and vehemence on all sides And from hence it comes to passe that by two contrary motions the one of the particles which go out of the burning Cole the other of those of the aethereall and watery substance
as Water 8 Another cause of Hardness from the fuller contact of Atomes Also how Hard things are broken 9 A third cause of Hardness from Heat 10 A fourth cause of Hardness from the motion of Atomes enclosed in a narrow space 11 How Hard things are Softned 12 Whence proceeds the spontaneous Restitution of things Bent. 13 Diaphanous and Opacous what they are and whence 14 The cause of Lightning and Thunder 15 Whence it proceeds that Clouds can fall again after they are once elevated and frozen 16 How it could be that the Moon was eclipsed when she was not diametrally opposite to the Sunne 17 By what means many Sunnes may appear at once 18 Of the Heads of Rivers 1 AS when the motion of the ambient aethereal substance makes the Spirits and fluid parts of our Bodies tend outwards we acknowledge Heat so by the endeavour inwards of the same spirits and humours we feel Cold. So that to Cool is to make the exterior parts of the Body endeavour inwards by a motion contrary to that of Calefaction by which the internal parts are called outwards He therefore that would know the cause of Cold must find by what motion or motions the exterior parts of any Body endeavour to retire inwards To begin with those Phaenomena which are the most familiar There is almost no man but knows that breath blown strongly and which comes from the mouth with violence that is to say the passage being straight will Cool the hand and that the same breath blown gently that is to say through a greater aperture wil warm the same The cause of which Phaenomenon may be this The breath going out hath two motiōs the one of the whole and direct by which the formost parts of the hand are driven inwards the other simple motion of the small particles of the same breath which as I have shewn in the 3d Article of the last Chapter causeth Heat According therefore as either of these Motions is predominant so there is the sense sometimes of Cold sometimes of Heat Wherefore when the breath is softly breathed out at a large passage that simple Motion which causeth Heat prevaileth and consequently Heat is felt and when by compressing the lips the breath is more strongly blown out then is the direct motion prevalent which makes us feel Cold. For the direct motion of the breath or aire is Wind and all Wind Cools or diminisheth former heat 2 And seeing not onely great Wind but almost any Ventilation and stirring of the Aire doth refrigerate the reason of many experiments concerning Cold cannot well be given without finding first what are the causes of Wind. Now Wind is nothing else but the direct motion of the Aire thrust forwards which nevertheless when many Winds concurre may be circular or otherwise indirect as it is in Whirle-winds Wherefore in the first place we are to enquire into the Causes of Winds Wind is Aire moved in a considerable quantity and that either in the manner of Waves which is both forwards also up down or else forwards onely Supposing therefore the Aire both cleer and calm for any time how little soever yet the greater Bodies of the World being so disposed and ordered as has been said it will be necessary that a Wind presently arise some where For seeing that motion of the parts of the Aire which is made by the Simple Motion of the Sunne in his own Epicycle causeth an exhalation of the particles of water from the Seas and all other moist Bodies and those particles make Clouds it must needs follow that whilest the particles of water pass upwards the particles of Aire for the keeping of all Spaces full be justled out on every side and urge the next particles and these the next till having made their circuit there comes continually so much Aire to the hinder parts of the Earth as there went water from before it Wherefore the ascending Vapours move the Aire towards the sides every way and all direct motion of the Aire being Wind they make a Wind. And if this Wind meet often with other Vapours which arise in other places it is manifest that the force thereof will be augmented the way or course of it changed Besides according as the Earth by its diurnal motion turns sometimes the drier sometimes the moister part towards the Sunne so sometimes a greater sometimes a less quantity of Vapours will be raised that is to say sometimes there will be a less sometimes a greater Wind. Wherefore I have rendred a possible cause of such Winds as are generated by Vapours and also of their Inconstancy From hence it follows that these Winds cannot be made in any place which is higher then that to which Vapours may ascend Nor is that incredible which is reported of the highest Mountains as the Pique of Tenariffe and the Andes of Peru namely that they are not at all troubled with these inconstant Winds And if it were certain that neither Rain nor Snow were ever seen in the highest tops of those Mountains it could not be doubted but that they are higher then any place to which Vapours use to ascend 3 Nevertheless there may be Wind there though not that which is made by the ascent of Vapours yet a less more constant Wind like the continued blast of a pair of bellows blowing from the East And this may have a double cause the one the diurnal mo tion of the Earth the other its simple motion in its own Epicycle For these Mountains being by reason of their height more eminent then all the rest of the parts of the Earth do by both these Motions drive the Aire from the West Eastwards To which though the diurnal Motion contribute but little yet seeing I have supposed that the simple Motion of the Earth in its own Epicycle makes two revolutions in the same time in which the diurnal Motion makes but one and that the Semidiameter of the Epicycle is double to the Semidiameter of the diurnal Conversion the Motion of every point of the Earth in its own Epicycle will have its velocity quadruple to that of the diurnal Motion so that by both these Motions together the tops of those Hils will sensibly be moved against the Aire and consequently a Wind will be felt For whether the Air strike the Sentient or the Sentient the Air the perception of Motion will be the same But this Wind seeing it is not caused by the ascent of Vapours must necessarily be very Constant. 4 When one Cloud is already ascended into the Aire if another Cloud ascend towards it that part of the Aire which is intercepted between them both must of necessity be pressed out every way Also when both of them whilest the one ascends and the other either stayes or descends come to be joyned in such manner as that the aethereal substance be shut within them on every side it will by this compression also go out by penetrating the Water
Hearer the Sound will come stronger then it would do through the open Aire And the cause not onley the possible but the certain and manifest cause is this that the Aire which is moved by the first breath and carried forwards in the Trunk is not diffused as it would be in the open Aire and is consequently brought to the eare almost with the same velocity with which it was first breathed out Whereas in the open Aire the first motion diffuseth it self every way into Circles such as are made by the throwing of a Stone into a standing water where the velocity grows less and less as the Undulation proceeds further and further from the beginning of its motion The second is this That if the Trunk be short and the end which is applyed to the mouth be wider then that which is applyed to the eare thus also the Sound will be stronger then if it were made in the open aire And the cause is the same namely that by how much the wider end of the Trunk is less distant from the beginning of the Sound by so much the less is the diffusion The third That it is easier for one that is within a Chamber to heare what is spoken without then for him that stands without to hear what is spoken within For the Windows and other inlets of the moved Aire are as the wide end of the Trunk And for this reason some creatures seem to hear the better because Nature has bestowed upon them wide and capacious Ears The fourth is this That though he which standeth upon the Sea shore cannot heare the Collision of the two neerest waves yet neverthess he hears the roaring of the whole Sea And the cause seems to be this that though the several collisions move the Organ yet they are not severally great enough to cause Sense whereas nothing hinders but that all of them together may make Sound 3 That Bodies when they are stricken do yeild some a more Grave others a more Acute Sound the cause may consist in the difference of the times in which the parts stricken and forced out of their places return to the same places again For in some Bodies the restitution of the moved parts is quick in others slow And this also may be the cause why the parts of the Organ which are moved by the Medium return to their rest again sometimes sooner sometimes later Now by how much the Vibrations or the reciprocal motions of the parts are more frequent by so much doth the whole Sound made at the same time by one stroke consist of more and consequently of smaller parts For what is Acute in Sound the same is Subtle in Matter and both of them namely Acute Sound and Subtle Matter consist of very small parts that of Time and this of the Matter it self The third distinction of Sounds cannot be conceived clearly enough by the names I have used of Clear and Hoarse nor by any other that I know and therefore it is needful to explain them by examples When I say Hoarse I understand Whispering and Hissing and whatsoever is like to these by what appellation soever it be expressed And Sounds of this kind seem to be made by the force of some strong Wind raking rather then striking such hard Bodies as it falls upon On the contrary when I use the word Clear I do not understand such a Sound as may be easily and distinctly heard for so Whispers would be Clear but such as is made by somewhat that is Broken and such as is Clamor Tinkling the Sound of a Trumpet c. and to express it significantly in one word Noise And seeing no Sound is made but by the concourse of two Bodies at the least by which concourse it is necessary that there be as well Reaction as Action that is to say one motion opposite to another it follows that according as the proportion between those two opposite motions is diversified so the Sounds which are made will be different from one another And whensoever the proportion between them is so great as that the motion of one of the Bodies be insensible if compared with the motion of the other then the Sound will not be of the same kind as when the Wind falls very obliquely upon a hard Body or when a hard Body is carried swiftly through the Aire for then there is made that Sound which I call a Hoarse Sound in Greek 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 Therefore the breath blown with violence from the mouth makes a Hissing because in going out it rakes the Superficies of the Lips whose reaction against the force of the breath is not Sensible And this is the cause why the Winds have that Hoarse Sound Also if two Bodies how hard soever be rubbed together with no great pressure they make a Hoarse Sound And this Hoarse Sound when it is made as I have said by the Aire raking the Superficies of a hard Body seemeth to be nothing but the dividing of the Aire into innumerable and very small Files For the asperity of the Superficies doth by the eminencies of its innumerable parts divide or cut in pieces the Aire that slides upon it 4 Noise or that which I call Clear Sound is made two wayes one by two Hoarse Sounds made by opposite motions the other by Collision or by the suddain pulling asunder of two Bodies whereby their small particles are put into commotion or being already in commotion suddenly restore themselves again which motion making impression upon the Medium is propagated to the Organ of Hearing And seeing there is in this Collision or divulsion an endeavour in the particles of one Body opposite to the endeavour of the particles of the other Body there will also be made in the Organ of Hearing a like opposition of endeavours that is to say of motions and consequently the Sound arising from thence will be made by two opposite motions that is to say by two opposite Hoarse Sounds in one and the same part of the Organ For as I have already said a Hoarse Sound supposeth the sensible motion of but one of the Bodies And this opposition of motions in the Organ is the cause why two Bodies make a Noyse when they are either suddenly stricken against one another or suddenly broken asunder 5 This being granted and seeing withall that Thunder is made by the vehement eruption of the Aire out of the cavities of congeled Clouds the cause of the great Noyse or Clap may be the suddain breaking asunder of the Ice For in this action it is necessary that there be not onely a great concussion of the small particles of the broken parts but also that this Concussion by being communicated to the Aire be carried to the Organ of Hearing make impression upon it And then from the first reaction of the Organ proceeds that first and greatest Sound which is made by the collision of the parts whilst they restore themselves And seeing there is
that is stricken be not onely sufficiently hard but have also the particles of which it consisteth like to one another both in hardness and figure such as are the particles of Glass and Metals which being first melted do afterwards settle and harden the Sound it yeildeth will because the motions of its parts and their reciprocations are like and Uniform be Uniform and pleasant and be more or less Lasting according as the Body stricken hath gteater or less magnitude The possible cause therefore of Sounds Uniform and Harsh and of their longer or shorter Duration may be one and the same likeness and unlikeness of the internal parts of the Sounding Body in respect both of their figure and hardness Besides if two plain Bodies of the same matter and of equal thickness do both yeild an Uniform Sound the Sound of that Body which hath the greatest extent of length will be the longest heard For the motion which in both of them hath its beginning from the point of percussion is to be propagated in the greater Body through a greater Space and consequently that propagation will require more time and therefore also the parts which are moved will require more time for their return Wherefore all the reciprocations cannot be finished but in longer time and being carried to the Eare will make the Sound last the longer And from hence it is manifest that of hard Bodies which yeild an Uniform Sound the Sound lasteth longer which comes from those that are round and hollow then from those that are plain if they be like in all other respects For in circular lines the action which begins at any point hath not frō the figure any end of its propagation because the line in which it is propagated returns again to its beginning so that the figure hinders not but that the motion may have infinite progression whereas in a plain every line hath its magnitude finite beyond which the action cannot proceed If therefore the matter be the same the motion of the parts of that Body whose figure is round and hollow wil last longer then of that which is plain Also if a string which is stretched be fastned at both ends to a hollow Body and be stricken the Sound will last longer then if it were not so fastned because the trembling or reciprocation which it receives from the stroke is by reason of the connexion communicated to the hollow Body and this trembling if the hollow Body be great will last the longer by reason of that greatness Wherefore also for the reason above mentioned the Sound will last the longer 9 In Hearing it happens otherwise then in Seeing that the action of the Medium is made stronger by the Wind when it blows the same way and weaker when it blows the contrary way The cause whereof cannot proceed from any thing but the different generation of Sound and Light For in the generation of Light none of the parts of the Medium between the object and the Eie are moved from their own places to other places sensibly distant but the action is propagated in spaces imperceptible so that no contrary Wind can diminish nor favourable Winde encrease the Light unless it be so strong as to remove the Object further off or bring it nearer to the Eie For the Wind that is to say the aire moved doth not by its interposition between the object and the eie worke otherwise then it would doe if it were stil and calme For where the pressure is perpetuall one part of the aire is no sooner carried away but another by succeeding it receives the same impression which the part carried away had received before But in the generation of Sound the first collision or breaking asunder beateth away driveth out of its place the nearest part of the aire and that to a considerable distance and with considerable velocity and as the circles grow by their remotenesse wider and wider so the aire being more more dissipated hath also its motion more more weakned Whensoever therfore the air is so stricken as to cause Sound if the Wind fall upon it it will move it all neerer to the Eare if it blow that way and further from it if it blow the contrary way so that according as it blowes from or towards the Object so the Sound which is heard will seeme to come from a neerer or remoter place and the action by reason of the unequall distances be strengthened or debilitated From hence may be understood the reason why the voice of such as are said to speake in their bellies though it be uttered neer hand is neverthelesse heard by those that suspect nothing as if it were a great way off For having no former thought of any determined place from which the voice should proceed and judging according to the greatesse if it be weake they thinke it a great way off if strong neer These Ventriloqui therefore by forming their voice not as others by the emission of their breath but by drawing it inwards doe make the same appear small and weake which weaknesse of the voice deceives those that neither suspect the artifice nor observe the endeavour which they use in speaking and so instead of thinking it weake they thinke it farre off 10 As for the Medium which conveighs Sound it is not Aire onely For Water or any other Body how hard soever may be that Medium For the Motion may be propagated perpetually in any hard continuous Body but by reason of the difficulty with which the parts of hard Bodies are moved the motion in going out of hard matter makes but a weak impression upon the Aire Nevertheless if one end of a very long and hard beam be stricken the eare be applyed at the same time to the other end so that when the action goeth out of the beam the aire which it striketh may immediately be received by the eare and be carried to the Tympanum the Sound will be considerably strong In like manner if in the night when all other noyse which may hinder Sound ceaseth a man lay his eare to the ground he will hear the Sound of the steps of Passengers though at a great distance because the motion which by their treading they communicate to the earth is propagated to the eare by the uppermost parts of the earth which receiveth it from their feet 11 I have shewn above that the difference between Grave and Acute Sounds consisteth in this that by how much the shorter the time is in which the reciprocations of the parts of a Body stricken are made by so much the more Acute will be the Sound Now by how much a Body of the same bigness is either more heavy or less stretched by so much the longer will the reciprocations last and therefore heavier and less stretched Bodies if they be like in all other respects will yeild a Graver Sound then such as be lighter and more stretched 12 For the finding out
of the cause of Smels I shall make use of the evidence of these following Phaenomena First that Smelling is hindred by Cold and helped by Heat Secondly that when the Wind bloweth from the Object the Smel is the stronger and contrarily when it bloweth from the Sentient towards the Object the weaker both which Phaenomena are by experience manifestly found to be true in Doggs which follow the track of Beasts by the Sent. Thirdly that such Bodies as are less pervious to the fluid Medium yeild less Smell then such as are more pervious as may be seen in Stones and Metals which compared with Plants and Living Creatures and their Parts Fruits and Excretions have very little or no Smell at all Fourthly that such Bodies as are of their own nature Odorous become yet more Odorous when they are bruised Fifthly that when the breath is stopped at least in Men nothing can be Smelt Sixthly that the sense of Smelling is also taken away by the stopping of the Nostrils though the mouth be left open 13 By the fourth and fifth Phaenomenon it is manifest that the first and immediate Organ of Smelling is the innermost cuticle of the Nostrils and that part of it which is below the passage common to the Nostrils and the Palate For when we draw breath by the Nostrils we draw it into the Lungs That breath therefore which conveighs Smels is in the way which passeth to the Lungs that is to say in that part of the Nostrils which is below the passage through which the breath goeth For nothing is Smelt neither beyond the passage of the breath within nor at all without the Nostrils And seeing that from different Smels there must necessarily proceed some mutation in the Organ and all mutation is motion it is therefore also necessary that in Smelling the parts of the Organ that is to say of that internal cuticle and the nerves that are inserted into it must be diversly moved by different Smels And seeing also that it hath been demonstrated that nothing can be moved but by a Body that is already moved and contiguous and that there is no other Body contiguous to the internal membrane of the nostrils but breath that is to say attracted aire and such little solid invisible Bodies if there be any such as are intermingled with the aire it follows necessarily that the cause of Smelling is either the motion of that pure aire or aethereal Substance or the motion of those small Bodies But this motion is an effect proceding from the Object of Smell and therefore either the whole Object it self or its several parts must necessarily be moved Now we know that Odorous Bodies make Odour though their whole bulk be not moved Wherefore the cause of Odour is the motion of the invisible parts of the Odorous Body And these invisible parts do either go out of the Object or else retaining their former situation with the rest of the parts are moved together with them that is to say they have simple and invisible motion They that say there goes something out of the Odorous Body call it an Effluvium which Effluvium is either of the aethereal substance or of the small Bodies that are intermingled with it But that all variety of Odours should proceed from the Effluviums of those small Bodies that are intermingled with the aethereal substance is altogether incredible for these considerations First that certain Unguents though very little in quantity do nevertheless send forth very strong Odours not onely to a great distance of place but also to a great continuance of time and are to be Smelt in every point both of that place and time so that the parts issued out are sufficient to fil ten thousand times more space then the whole Odorous Body is able to fill which is impossible Secondly that whether that issuing out be with straight or with crooked motion if the same quantity should flow from any other Odorous Body with the same motion it would follow that all Odorous Bodies would yeild the same Smell Thirdly that seeing those Effluviums have great Velocity of motion as is manifest from this that noysome Odours proceeding from caverns are presently Smelt at a great distance it would follow that by reason there is nothing to hinder the passage of those Effluviums to the Organ such motion alone were sufficient to cause Smelling Which is not so for we cannot Smell at all unless we draw in our breath through our Nostrils Smelling therefore is not caused by the Effluvium of Atomes nor for the same reason is it caused by the Effluvium of aethereal substance for so also we should Smell without the drawing in of our breath Besides the aethereal substance being the same in all Odorous Bodies they would always affect the Organ in the same manner and consequently the Odours of all things would be like It remains therefore that the cause of Smelling must consist in the Simple motion of the parts of Odorous Bodies without any efflux or diminution of their whole substance And by this motion there is propagated to the Organ by the intermediate aire the like motion but not strong enough to excite Sense of it self without the attraction of aire by respiration And this is a possible cause of Smelling 14 The cause why Smelling is hindred by Cold and helped by Heat may be this that Heat as hath been shewn in the 21 Chapter generateth Simple motion and therefore also wheresoever it is already there it will encrease it and the cause of Smelling being encreased the Smell it self will also be encreased As for the cause why the Wind blowing from the Object makes the Smell the stronger it is all one with that for which the attraction of aire in respiration doth the same For he that draws in the aire next to him draws with it by succession that aire in which is the Object Now this motion of the aire is Wind and when another Wind bloweth from the Object will be encreased by it 15 That Bodies which cōtain the least quantity of air as Stones and Metals yeild less Smell then Plants and Living Creatures the cause may be that the motion which causeth Smelling is a motion of the fluid parts onely which parts if they have any motion from the hard parts in which they are contained they communicate the same to the open aire by which it is propagated to the Organ Where therefore there are no fluid parts as in Metals or where the fluid parts receive no motion from the hard parts as in Stones which are made hard by accretion there can be no Smell And therefore also the Water whose parts have little or no motion yeildeth no Smell But if the same Water by Seeds and the heat of the Sunne be together with particles of Earth raised into a Plant and be afterwards pressed out again it will be Odorous as Wine from the Vine And as Water passing through plants is by the motion
because they are Principles cannot be demonstrated and seeing they are known by Nature as was said above in the 5th Article they need no Demonstration though they need Explication The whole Method therefore of Demonstration is Syntheticall consisting of that order of Speech which begins from Primary or most Universall Propositions which are manifest of themselves and proceeds by a perpetuall composition of Propositions into Syllogismes till at last the Learner understand the truth of the Conclusion sought after 13 Now such Principles are nothing but Definitions whereof there are two sorts one of Names that signifie such things as have some conceiveable Cause and another of such Names as signifie things of which we can conceive no Cause at all Names of the former kind are Body or Matter Quantity or Extension Motion and whatsoever is common to all Matter Of the second kind are such a Body such and so great Motion so great Magnitude such Figure and whatsoever we can distinguish one Body from another by And Names of the former kind are well enough defined when by Speech as short as may be we raise in the Mind of the Hearer perfect and cleer Ideas or Conceptions of the Things named as when we Define Motion to be the leaving of one place and the acquiring of another continually for though no Thing Moved nor any Cause of Motion be in that Definition yet at the hearing of that Speech there will come into the Mind of the Hearer an Idea of Motion clâ—er enough But Definitions of things which may be understood to have some Cause must consist of such Names as expresse the Cause or Manner of their Generation as when we Define a Circle to be a Figure made by the circumduction of a straight line in a plaine c. Besides Definitions there is no other Proposition that ought to be called Primary or according to severe truth be received into the number of Principles For those Axiomes of Euclide seeing they may be demonstrated are no Principles of Demonstration though they have by the consent of all Men gotten the authority of Principles because they need not be Demonstrated Also those Petitious or Postulata as they call them though they be Principles yet they are not Principles of Demonstration but of Construction onely that is not of Science but of Power or which is all one not of Theoremes which are Speculations but of Problemes which belong to Practice or the doing of something But as for those common received Opinions Nature abhorres Vanity Nature doth nothing in Vaine and the like which are neither evident in themselves nor at all to be demonstrated and which are oftner false then true they are much lesse to be ackowledged for Principles To returne therefore to Definitions The reason why I say that the Cause and Generation of such things as have any Cause or Generation ought to enter into their Definitions is this The End of Science is the Demonstration of the Causes and Generations of Things which if they be not in the Definitions they cannot be found in the Conclusion of the first Syllogisme that is made from those Definitions and if they be not in the first Conclusion they will not be found in any further Conclusion deduced from that and therefore by proceeding in this manner we shall never come to Science which is against the scope and intention of Demonstration 14 Now seeing Definitions as I have said are Principles or Primary Propositions they are therefore Speeches and seeing they are used for the raising of an Idea of some Thing in the mind of the Learner whensoever that Thing has a Name the Definition of it can be nothing but the Explication of that Name by Speech and if that Name be given it for some compounded Conception the Definition is nothing but a Resolution of that Name into its most Universall parts As when we define Man saying Man is a Body Animated Sentient Rationall those Names Body Animated c. are parts of that whole Name Man so that Definitions of this kind alwayes consist of Genus and Difference the former Names being all till the last Generall and the last of all Difference But if any Name be the most Universall in its kind then the Definition of it cannot consist of Genus and Difference but is to be made by such circumlocution as best explicateth the force of that Name Again it is possible and happens often that the Genus and Difference are put together and yet make no Definition as these Words a Straight Line containe both the Genus and Difference but are not a Definition unlesse we should thinke a Straight Line may be thus defined A Straight Line is a Straight Line and yet if there were added another Name consisting of different Words but signifying the same thing which these signifie then these might be the Definition of that Name From what has been said it may be understood how a Definition ought to be defined namely That it is a Proposition whose Praedicate Resolves the Subiect when it may and when it may not it exemplifies the same 15 The Properties of a Definition are First that it takes away Aequivocation as also all that multitude of Distinctions which are used by such as think they may learn Philosophy by Disputation For the Nature of a Definition is to define that is to determine the signification of the defined Name and to pare from it all other Signification besides what is contained in the Definition it selfe and therefore one Definition does as much as all the Distinctions how many soever that can be used about the Name defined Secondly That it gives an Universall Notion of the thing defined representing a certaine Universall Picture thereof not to the Eye but to the Mind For as when one paints a Man he paints the image of some Man so he that defines the Name Man makes a Representation of some Man to the mind Thirdly That it is not necessary to dispute whether Definitions are to be admitted or no. For when a Master is instructing his Scholar if the Scholar understand all the parts of the thing defined which are Resolved in the Definition and yet will not admit of the Definition there needs no further Controversie betwixt them it being all one as if he refused to be taught But if he understand nothing then certainely the Definition is faulty for the nature of a Definition consists in this that it exhibit a cleare Idea of the thing defined and Principles are either known by themselves or else they are not Principles Fourthly That in Philosophy Definitions are before defined Names For in teaching Philosophy the first beginning is from Definitions and all progression in the same till we come to the Knowledge of the thing compounded is Compositive Seeing therefore Definition is the explication of a Compounded Name by Resolution and the progression is from the parts to the compound Definitions must be understood before Compounded Names nay when
the Earth was before the Wind it self and if the Earth were Moved before the Wind was made then the Wind could not be the cause of the Earths revolution but if the Sunne were Moved and the Earth stand still then it is manifest the Earth might remain Unmoved notwithstanding that Wind and therefore that motion was not made by the Cause which he alledgeth But Parallogismes of this kind are very frequent among the Writers of Physiques though none can be more elaborate then this in the Example given 19 It may to some men seem pertinent to treat in this place of that Art of the Geometricians which they call Logistica that is the Art by which from supposing the thing in question to be true they proceed by Ratiocination till either they come to something knowne by which they may demonstrate the truth of the thing sought for or to something which is impossible from whence they collect that to be false which they supposed true But this Art cannot be explicated here for this reason that the Method of it can neither be practised nor understood unlesse by such as are well versed in Geometry and among Geometricians themselves they that have most Theoremes in readiness are the most ready in the use of this Logistica so that indeed it is not a distinct thing from Geometry it selfe for there are in the Method of it three parts the first whereof consists in the finding out of Equality betwixt known and unknown things which they call Equation and this Equation cannot be found out but by such as know perfectly the Nature Properties and Transpositions of Proportion as also the Addition Substraction Multiplication and Division of Lines and Superficies and the Extraction of Roots which are the parts of no meane Geometrician The Second is when an Equation is found to be able to judge whether the Truth or Falsity of the Question may be deduced from it or no which yet requires greater Knowledge And the third is when such an Equation is found as is fit for the solution of the Question to know how to Resolve the same in such manner that the Truth or Falsity may thereby manifestly appeare which in hard questions cannot be done without the Knowledge of the Nature of Crooked-lined Figures but he that understands readily the Nature and Properties of these is a Compleat Geometrician It happens besides that for the finding out of Equations there is no certaine Method but he is best able to do it that has the best Naturall Wit THE FIRST GROVNDS OF PHILOSOPHY CHAP. VII Of Place and Time 1 Things that have no existence may neverthelesse be under stood and computed 2 What is space 3 Time 4 Part. 5 Division 6 One 7 Number 8 Composition 9 The Whole 10 Spaces and Times Contiguous and Continuall 11 Beginning End Way Finite Infinite 12 What is Infinite in Power Nothing Infinite can be truly said to be either Whole or One Nor Infinite Spaces or Times Many 13 Division proceeds not to the Least 1 IN the Teaching of Naturall Philosophy I cannot begin better as I have already shewn then from Privation that is from feigning the World to be annihilated But if such annihilation of all things be supposed it may perhaps be asked what would remain for any Man whom onely I except from this Universal annihilation of things to consider as the Subject of Philosophy or at all to reason upon or what to give Names unto for Ratiocinations sake I say therefore there would remain to that Man Ideas of the World and of all such Bodies as he had before their annihilation seen with his eies or perceived by any other Sense that is to say the Memory and Imagination of Magnitudes Motions Sounds Colours c. as also of their order parts All w ch things though they be nothing but Ideas Phantasms hapning internally to him that imagineth yet they will appear as if they were externall and not at all depending upon any power of the Mind And these are the things to which he would give Names and substract them from and compound them with one another For seeing that after the destruction of all other things I suppose Man still remaining and namely that he thinkes imagines and remembers there can be nothing for him to thinke of but what is Past Nay if we do but observe diligently what it is we doe when we consider and reason we shall find that though all things be still remaining in the world yet we compute nothing but our own Phantasmes For when we calculate the magnitude and motions of Heaven or Earth we doe not ascend into Heaven that we may divide it into parts or measure the motions thereof but we doe it sitting still in our Closets or in the Darke Now things may be considered that is be brought into Account either as internal Accidents of our Mind in which manner we consider them when the question is about some Faculty of the Mind or as Species of external things not as really existing but appearing onely to exist or to have a Being without Us. And in this manner we are now to consider them 2 If therefore we remember or have a Phantasme of any thing that was in the world before the supposed annihilation of the same and consider not that the thing was such or such but onely that it had a Being without the Mind we have presently a Conception of that we call Space an Imaginary Space indeed because a meere Phantasme yet that very thing which all men call so For no man calls it Space for being already filled but because it may be filled nor does any man think Bodies carry their Places away with them but that the same Space contains sometimes one sometimes another Body which could not be if Space should alwayes accompany the Body which is once in it And this is of it selfe so manifest that I should not thinke it needed any explaining at all but that I finde Space to be falsely defined by certaine Philosophers who inferre from thence One that the world is Infinite for taking Space to be the Extension of Bodies and thinking Extension may encrease continually he inferres that Bodies may be infinitely Extended and Another from the same Definition concludes rashly that it is impossible even to God himselfe to create more Worlds then one for if another World were to be created he sayes that seeing there is nothing without this world and therefore according to his Definition no Space that new world must be placed in nothing but in nothing nothing can be placed which he affirms onely without shewing any reason for the same whereas the contrary is the truth for more cannot be put into a Place allready filled so much is Empty Space fitter then that which is Full for the receiving of new Bodies Having therefore spoken thus much for these mens sakes and for theirs that assent to them I return to my purpose and define Space thus
produced and Power in respect of the same Effect to be produced hereafter so that Cause respects the Past Power the Future time Also the Power of the Agent is that which is commonly called Active Power In like manner whensoever any Patient has all those Accidents which it is requisite it should have for the production of some Effect in it we say it is in the Power of that Patient to produce that Effect if it be applyed to a fitting Agent But those Accidents as is defined in the precedent Chapter constitute the Material Cause and therefore the Power of the Patient commonly called Passive Power and Material Cause are the same thing but with this different consideration that in Cause the Past time and in Power the Future is respected Wherefore the Power of the Agent and Patient together which may be called Entire or Plenary Power is the same thing with Entire Cause for they both consist in the Sum or Aggregate of all the Accidents as well in the Agent as in the Patient which are requisite for the production of the Effect Lastly as the Accident produced is in respect of the Cause called an Effect so in respect of the Power it is called an Act. 2 As therefore the Effect is produced in the same instant in which the Cause is Entire so also every Act that may be produced is produced in the same instant in which the Power is Plenary And as there can be no Effect but from a Sufficient and Necessary Cause so also no Act can be produced but by Sufficient Power or that Power by which it could not but be produced 3 And as it is manifest as I have shewn that the Efficient and Material Causes are severally and by themselves parts onely of an Entire Cause and cannot produce any Effect but by being joyned together so also Power Active and Passive are parts onely of Plenary and Entire Power nor except they be joyned can any Act proceed from them and therefore these Powers as I said in the first Article are but conditionall namely the Agent has Power if it be applyed to a Patient and the Patient has Power if it be applyed to an Agent otherwise neither of them have Power nor can the Accidents which are in them severally be properly called Powers nor any Action be said to be Possible for the Power of the Agent alone or of the Patient alone 4 For that is an Impossible Act for the production of which there is no Power Plenary For seeing Plenary Power is that in which all things concurre which are requisite for the production of an Act if the Power shall never be Plenary there will always be wanting some of those things without which the Act cannot be produced wherefore that Act shall never be produced that is that Act is IMPOSSIBLE And every Act which is not Impossible is POSSIBLE Every Act therefore which is Possible shall at some time be produced for if it shall never be produced then those things shall never concurre which are requisite for the production of it wherefore that Act is Impossible by the Definition which is contrary to what was supposed 5 A Necessary Act is that the production whereof it is Impossible to hinder and therefore every Act that shall be produced shall necessarily be produced for that it shall not be produced is Impossible because as is already demonstrated every Possible Act shall at some time be produced Nay this Proposition What shall be shall be is as necessary a Proposition as this A Man is a Man But here perhaps some man may ask whether those Future things which are commonly called Contingents are Necessary I say therefore that generally all Contingents have their Necessary Causes as is shewn in the preceding Chapter but are called Contingents in respect of other Events upon which they do not depend as the Rain which shall be to morrow shall be Necessarily that is from necessary Causes but we think and say it happens by chance because we doe not yet perceive the Causes thereof though they exist now for men commonly call that Casuall or Contingent whereof they do not perceive the necessary Cause and in the same manner they use to speake of things past when not knowing whether a thing be done or no they say it is possible it never was done Wherefore all Propositions concerning Future things contingent or not contingent as this It will rayne to morrow or this To morrow the Sun will rise are either necessarily true or necessarily false but we call them Contingent because we doe not yet know whether they be true or false whereas their Verity depends not upon our Knowledge but upon the foregoing of their Causes But there are some who though they confess this whole Proposition To morrow it will either rain or not rain to be true yet they will not acknowledge the parts of it as To morrow it will rain or To morrow it will not rain to be either of them true by it self because they say neither this nor that is true determinately But what is this determinately true but true upon our knowledge or evidently true and therefore they say no more but that it is not yet known whether it be true or no but they say it more obscurely and darken the Evidence of the truth with the same words with which they endevour to hide their own ignorance 6 In the 9th Article of the precedent Chapter I have shewn that the Efficient Cause of all Motion and Mutation consists in the Motion of the Agent or Agents And in the first Article of this Chapter that the Power of the Agent is the same thing with the Efficient Cause From whence it may be understood that all Active Power consists in Motion also and that Power is not a certain Accident which differs from all Acts but is indeed an Act namely Motion which is therefore called Power because another Act shall be produced by it afterwards For example if of three Bodies the first put forwards the second and this the third the Motion of the second in respect of the first which produceth it is the Act of the second Body but in respect of the third it is the Active Power of the same second Body 7 The Writers of Metaphysiques reckon up two other Causes besides the Efficient and Material namely the ESSENCE which some call the Formal Cause and the End or Final Cause both which are nevertheless Efficient Causes For when it is said the Essence of a thing is the Cause thereof as to be Rational is the Cause of Man it is not intelligible for it is all one as if it were said To be a Man is the Cause of Man which is not well said And yet the knowledge of the Essence of any thing is the Cause of the knowledge of the thing it selfe for if I first know that a thing is Rational I know from thence that the same is Man but this is no
all Opinions concerning the nature of Infinite and Eternal known onely to himself should as the first-fruits of Wisdom be judged by those whose Ministery he meant to use in the ordering of Religion I cannot therefore commend those that boast they have demonstrated by reasons drawn from natural things that the World had a Beginning They are contemned by Idiots because they understand them not and by the Learned because they understand them by both deservedly For who can commend him that demonstrates thus If the World be Eternal then an infinite number of dayes or other measures of Time preceded the birth of Abraham But the birth of Abraham preceded the birth of Isaac and therefore one Infinite is greater then another Infinite or one Eternal then another Eternal which he sayes is absurd This Demonstration is like his who from this that the number of even Numbers is infinite would conclude that there are as many even Numbers as there are Numbers simply that is to say the even Numbers are as many as all the even and od together They which in this manner take away Eternity from the World do they not by the same means take away Eternity from the Creator of the Woâ—ld From this absurdity therefore they run into another being forced to call Eternity Nunc stans a standing still of the present Time or an abiding Now and which is much more absurd to give to the infinite number of Numbers the name of Unity But why should Eternity be called an Abiding Now rather then an Abiding Then Wherefore there must either be many Eternities or Now and Then must signifie the same With such Demonstrators as these that speak in another language it is impossible to enter into disputation And the men that reason thus absurdly are not Idiots but which makes the absurdity unpardonable Geometricians and such as take upon them to be Judges impertinent but severe Judges of other mens Demonstrations The reason is this that as soon as they are entangled in the Words Infinite and Eternal of which we have in our mind no Idea but that of our own insufficiency to comprehend them they are forced either to speak something absurd or which they love worse to hold their peace For Geometry hath in it somewhat like Wine which when new is windy but afterwards though less pleasant yet more wholsome Whatsoever therefore is true young Geometricians think Demonstrable but elder not Wherefore I purposely pass over the Questions of Infinite and Eternal contenting my self with that Doctrine concerning the Beginning and Magnitude of the World which I have been perswaded to by the holy Scriptures and fame of the Miracles which confirm them and by the Custome of my Country and reverence due to the Laws And so I pass on to such things as it is not unlawful to dispute of 2 Concerning the World it is further questioned whether the parts thereof be contiguous to one another in such manner as not to admit of the least empty space between and the disputation both for against it is carried on with probability enough For the taking away of Vacuum I will instance in onely one experiment a common one but I think unanswerable Let AB in the first fig. represent a vessel such as Gardiners use to water their Gardens withal whose bottom B is ful of litle holes whose mouth A may be stopt with ones finger when there shall be need If now this vessel be filled with water the hole at the top A being stopt the water will not flow out at any of the holes in the bottom B. But if the finger be removed to let in the air above it will run out at them all and as soon as the finger is applyed to it again the water wil suddenly totally be stayed again from running out The cause whereof seems to be no other but this that the Water cannot by its natural endeavour to descend drive down the aire below it because there is no place for it to go into unless either by thrusting away the next contiguous aire it proceed by continual endeavour to the hole A where it may enter and succeed into the place of the water that floweth out or else by resisting the endeavour of the water Downwards penetrate the same and pass up through it By the first of these wayes while the hole at A remains stopped there is no possible passage nor by the second unless the holes be so great that the water flowing out at them can by its own waight force the Air at the same time to ascend into the vessel by the same holes as we see it does in a vessel whose mouth is wide enough when we turn suddenly the bottom upwards to poure out the water for then the Aire being forced by the waight of the water enters as is evident by the sobbing and resistance of the water at the sides or circumference of the orifice And this I take for a sign that all Space is full for without this the naturall motion of the water which is a heavy Body downwards would not be hindered 3 On the contrary for the establishing of Vacuum many specious arguments and experiments have been brought Neverthelesse there seemes to be something wanting in all of them to conclude it firmely These arguments for Vacuum are partly made by the followers of the doctrine of Epicurus who taught that the World consists of very small Spaces not filled by any Bodie and of very small Bodies that have within them no empty Space which by reason of their hardnesse he calls Atomes and that these small Bodies and Spaces are every where intermingled Their arguments are thus delivered by Lucretius And first he sayes that unlesse it were so there could be no motion For the office and property of Bodies is to withstand and hinder motion If therfore the Universe were filled with Body motion would every where be hindered so as to have no beginning any where consequently there would be no motion at all It is true that in whatsoever is full and at rest in all its parts it is not possible motion should have beginning But nothing is drawn from hence for the proving of Vacuum For though it should be granted that there is Vacuum yet if the Bodies which are intermingled with it should all at once and together be at rest they would never be moved again For it has been demonstrated above in the 9th Chapter 7th Article that nothing can be moved but by that which is contiguous and already moved But supposing that all things are at rest together there can be nothing contiguous and moved and therefore no beginning of motion Now the denying of the beginning of motion doth not take away present motion unless beginning be taken away from Body also For motion may be either coeternal or concreated with Body Nor doth it seem more necessary that Bodies were first at rest and afterwards moved then that they were
first moved and rested if ever they rested at all afterwards Neither doth there appear any cause why the matter of the World should for the admission of motion be intermingled with empty spaces rather then full I say full but withall fluid Nor lastly is there any reason why those hard Atomes may not also by the motion of intermingled fluid matter be congregated brought together into compounded Bodies of such bigness as we see Wherefore nothing can by this argument be concluded but that motion was either coeternal or of the same duration with that which is moved neither of which conclusions consisteth with the doctrine of Epicurus who allows neither to the World nor to Motion any Beginning at all The necessity therefore of Vacuum is not hitherto demonstrated And the cause as far as I understand from them that have discoursed with me of Vacuum is this that whilest they contemplate the nature of Fluid they conceive it to consist as it were of small grains of hard matter in such manner as meal is fluid made so by grinding of the Corn when nevertheless it is possible to conceive Fluid to be of its own nature as homogeneous as either an Atome or as Vacuum it self The second of their arguments is taken from waight and is contained in these Verses of Lucretius Corporis officium est quoniam premere omnia deorsum Contrà autem natura manet sine Pondere Inanis Ergo quod magnum est aeque Leviusque videtur Nimirum plus esse sibi declarat Inanis That is to say Seeing the office and property of Body is to press all things downwards and on the contrary seeing the nature of Vacuum is to have no waight at all Therefore when of two Bodies of equal magnitude one is lighter then the other it is manifest that the lighter Body hath in it more Vacuum then the other To say nothing of the Assumption concerning the endeavour of Bodies downwards which is not rightly assumed because the World hath nothing to do with Downwards which is a mere fiction of ours Nor of this that if al things tended to the same lowest part of the World either there would be no coalescence at all of Bodies or they would all be gathered together into the same place This onely is sufficient to take away the force of the argument that Aire intermingled with those his Atomes had served as well for his purpose as his intermingled Vacuum The third argument is drawn from this That Lightning Sound Heat and Cold do penetrate all Bodies except Atomes how solid soever they be But this reason except it be first demonstrated that the same things cannot happen without Vacuum by perpetual generation of Motion is altogether invalid But that all the same things may so happen shall in due place be demonstrated Lastly the fourth argument is set down by the same Lucretius in these Verses Duo de concursu corpora lata Si citò dissiliant nempe aer omne necesse est Inter corpora quod fuerat possidat Inane Is porro quamvis circum celerantibus auris Confluat haud poterit tamen uno tempore totum Compleri spatium nam primum quemque necesse est Occupet ille locum deinde omnia possideantur That is If two flat Bodies be suddenly pulled asunder of necessity the Air must come between them to fill all the space they left empty But with what celerity soever the Air flow in yet it cannot in one instant of time fill the whole space but first one part of it then successively all Which nevertheless is more repugnant to the opinion of Epicurus then of those that deny Vacuum For though it be true that if two Bodies were of infinite hardness and were joyned together by their Superficies which were most exactly plain it would be impossible to pull them asunder in regard it could not be done but by Motion in an instant yet if as the greatest of all Magnitudes cannot be given nor the swiftest of all Motions so neither the hardest of all hard Bodies it might be that by the application of very great force there might be place made for a successive flowing in of the Aire namely by separating the parts of the joyned Bodies by succession beginning at the outermost and ending at the innermost part He ought therefore first to have proved that there are some Bodies extreamly hard not relatively as compared with softer Bodies but absolutely that is to say infinitely hard which is not true But if we suppose as Epicurus doth that Atomes are indivisible and yet have small superficies of their own then if two Bodies should be joyned together by many or but one onely small superficies of either of them then I say this argument of Lucretius would be a firme demonstration that no two Bodies made up of Atomes as he supposes could ever possibly be pulled asunder by any force whatsoever But this is repugnant to daily experience And thus much of the arguments of Lucretius Let us now consider the arguments which are drawn from the experiments of later Writers 4 The first experiment is this That if a hollow vessel be thrust into water with the bottom upwards the water will ascend into it which they say it could not do unless the Aire within were thrust together into a narrower place and that this were also impossible except there were little empty places in the Aire Also that when the Aire is compressed to a certain degree it can receive no further compression its small particles not suffering themselves to be pent into less room This reason if the Aire could not pass through the Water as it ascends within the vessel might seem valid But it is sufficiently known that Aire will penetrate Water by the application of a force equal to the gravity of the Water If therefore the force by which the Vessel is thrust down be greater or equal to the endeavour by which the water naturally tendeth downwards the Aire will go out that way where the resistance is made namely towards the edges of the Vessel For by how much the deeper is the water which is to be penetrated so much greater must be the depressing force But after the Vessel is quite under water the force by which it is depressed that is to say the force by which the water riseth up is no longer encreased There is therefore such an equilibration between them as that the natural endeavour of the water downwards is equal to the endeavour by which the same water is to be penetrated to the encreased depth The second experiment is That if a concave Cylinder of sufficient length made of Glass that the experiment may be the better seen having one end open and the other close shut be filled with Quicksilver and the open end being stopped with ones finger be together with the finger dipped into a dish or other vessel in which also there is Quicksilver and the Cylinder be set upright we
conversion of the Earth by which conversion all things that adhere to its superficies are necessarily carried about with it may be referred the three Phaenomena concerning the Tides of the Ocean Whereof the first is the alternate elevation and depression of the Water at the Shores twice in the space of 24 houres and neer upon 52 minutes for so it has constantly continued in all ages The second that at the New and Full Moons the elevations of the Water are greater then at other times between And the third that when the Sunne is in the Equinoctial they are yet greater then at any other time For the salving of which Phaenomena we have already the foure above-mentioned Motions to which I assume also this that the part of the Earth which is called America being higher then the Water and extended almost the space of a whole Semicircle from North to South gives a stop to the motion of the Water This being granted In the same 4th figure where l b k c is supposed to be in the plain of the Moons monethly motion let the little Circle l d k e be described about the same Center a in the plain of the Equinoctial This Circle therefore will decline from the Circle l b k c in an angle of almost 28 degrees and ½ for the greatest declination of the Ecliptick is 23½ to which adding 5 for the greatest declination of the Moon from the Ecliptick the summe wil be 28 degrees and ½ Seeing now the Waters which are under the Circle of the Moons course are by reason of the Earths Simple Motion in the plain of the same Circle moved together with the Earth that is to say together with their own bottoms neither out-going nor out-gone if we add the Diurnal motion by which the other Waters which are under the Equinoctial are moved in the same order and consider withall that the Circles of the Moon and of the Equinoctial intersect one another it will be manifest that both those Waters which are under the Circle of the Moon and under the Equinoctiall will runne together under the Equinoctial and consequently that their Motion will not onely be swifter then the ground that carries them but also that the waters themselves will have greater elevation whensoever the Earth is in the Equinoctial Wherefore whatsoever the cause of the Tides may be this may be the cause of their augmentation at that time Againe seeing I have supposed the Moon to be carried about by the simple motion of the Earth in the little circle lbkc and demonstrated at the 4 article of the 21 chapter that whatsoever is moved by a Movent that hath simple motion will be moved allwayes with the same velocity it follows that the center of the Earth will be carried in the circumference lbkc with the same velocity with which the Moon is carried in the circumference mnop Wherefore the time in which the Moon is carried about in mnop is to the time in which the Earth is carried about in lbkc as one circumference to the other that is as ao to ak But ao is observed to be to the Semidiameter of the Earth as 59 to 1 and therefore the Earth if ak be put for its Semidiameter will make 59 revolutions in lbkc in the time that the Moon makes one monthly circuit in mnop But the Moon makes her monthly circuit in little more then 29 dayes Wherefore the Earth shal make its circuit in the circumference lbkc in 12 hours and a little more namely about 26 minutes more that is to say it shall make two circuits in 24 hours and allmost 52 minutes which is observed to be the time between the high water of one day and the high water of the day following Now the course of the waters being hindered by the southern part of America their motion will be interrupted there and consequently they will be elevated in those places and sink down again by their own waight twice in the space of 24 hours and 52 minutes And thus I have given a possible cause of the diurnall reciprocation of the Ocean Now from this swelling of the Ocean in those parts of the Earth proceed the Flowings and Ebbings in the Atlantick Spanish Brittish and German Seas which though they have their set times yet upon severall Shores they happen at severall hours of the day and they receive some augmentation from the North by reason that the shores of China and Tartaria hindering the generall course of the waters makes them swell there and discharge themselves in part through the straight of Anian into the Northern Ocean and so into the German Sea As for the Spring Tides which happen at the time of the New Full Moons they are caused by that simple motion which at the beginning I supposed to be allwayes in the Moone For as when I shewed the cause of the Excentricity of the Earth I derived the elevation of the waters from the simple motion of the Sunne so the same may here be derived from the simple motion of the Moon For though from the generation of Clouds there appeare in the Sunne a more manifest power of elevating the waters then in the Moon yet the power of encreasing moisture in Vegetables and living creatures appears more manifestly in the Moon then in the Sunne which may perhaps proceed from this that the Sunne raiseth up greater and the Moon lesser drops of water Neverthelesse it is more likely and more agreeable to common observation that Raine is raised not only by the Sunne but also by the Moon for allmost all men expect change of weather at the time of the Conjunctions of the Sunne and Moon with one another and with the Earth more then in the time of their Quarters In the last place the cause why the Spring Tides are greater at the time of the Aequinoxes hath been already sufficiently declared in this Article where I have demonstrated that the two Motions of the Earth namely its Simple Motion in the little Circle lbkc and its Diurnal motion in ldke cause necessarily a greater elevation of Waters when the Sunne is about the Aequinoxes then when he is in other places I have therefore given possible causes of the Phaenomenon of the Flowing and Ebbing of the Ocean 11 As for the explication of the yearly Praecession of the Aequinoctial points we must remember that as I have already shewn the annual motion of the Earth is not in the Circumference of a Circle but of an Ellipsis or a line not considerably different from that of an Ellipsis In the first place therefore this Elliptical line is to be described Let the Ecliptick ♎ ♑ ♈ ♋ in the 5th figure be divided into four equal parts by the two straight lines ab and ♑ ♋ cutting one another at right angles in the Center c and taking the Arch bd of 2 degrees and 16 minutes let the straight line de be drawn parallel to ab and cutting ♑ ♋ in f
which being done the Excentricity of the Earth will be cf. Seeing therefore the annual motion of the Earth is in the Circumference of an Ellipsis of which ♑ ♋ is the greater Axis ab cannot be the lesser Axis for ab and ♑ ♋ are equal Wherefore the Earth passing through a b will either pass above ♑ as through g or passing through ♑ will fall between c and a it is no matter which Let it pass therefore through g and let gl be taken equal to the straight line ♑ ♋ and dividing gl equally in i gi will be equal to ♑ ♋ il equal to f ♋ and consequently the point i will cut the Excentricity cf into two equal parts and taking ih equal to if hi will be the whole Excentricity If now a straight line namely the line ♎ i ♈ be drawn through i parallel to the straight lines ab and ed the way of the Sunne in Summer namely the Arch ♎ g ♈ will be greater then his way in Winter by 8 degrees and ¼ Wherefore the true Aequinoxes wil be in the straight line ♎ i ♈ and therefore the Ellipsis of the Earths annual motion will not pass through a g b l but through ♎ g ♈ l. Wherfore the annual motion of the Earth is in the Ellipsis ♎ g ♈ l and cannot be the Excentricity being salved in any other line And this perhaps is the reason why Kepler against the opinion of all the Astronomers of former time thought fit to bisect the Excentricity of the Earth or according to the Ancients of the Sunne not by diminishing the quantity of the same Excentricity because the true measure of that quantity is the difference by which the Summer Arch exceeds the Winter Arch but by taking for the Center of the Ecliptick of the great Orbe the point c neerer to f so placing the whole great Orbe as much neerer to the Ecliptick of the fixed Stars towards ♋ as is the distance between c i. For seeing the whole great Orbe is but as a point in respect of the immense distance of the fixed Starres the two straight lines ♎ ♈ and ab being produced both wayes to the beginnings of Aries and Libra will fall upon the same points of the Sphere of the fixed Stars Let therefore the Diameter of the Earth mn be in the plain of the Earths annual motion If now the Earth be moved by the Sunnes simple motion in the Circumference of the Ecliptick about the Center i this Diameter will bee kept alwayes parallel to itself and to the straight line gl But seeing the Earth is moved in the Circumference of an Ellipsis without the Ecliptick the point n whilst it passeth through ♎ ♑ ♈ will go in a lesser Circumference then the point m and consequently as soon as ever it begins to be moved it will lose its parallelisme with the straight line ♑ ♋ so that mn produced will at last cut the straight line gl produced And contrarily as soon as mn is past ♈ the Earth making its way in the internal Ellipticall line ♈ l ♎ the same mn produced towards m will cut lg produced And when the Earth hath allmost finished its whole circumference the same mn shall againe make a right angle with a line drawn from the center i a little short of the point from which the Earth began its motion And there the next yeare shall be one of the Aequinoctial points namely neer the end of ♠the other shall be opposite to it neer the end of ♓ And thus the points in which the Days and Nights are made equall doe every year fall back but with so slow a motion that in a whole year it makes but 51 first minutes And this relapse being contrary to the order of the Signes is commonly called the Praecession of the Aequinoxes Of which I have from my former Suppositions deduced a possible cause which was to be done According to what I have said concerning the cause of the Excentricity of the Earth and according to Kepler who for the cause thereof supposeth one part of the Earth to be affected to the Sunne the other part to be disaffected the Apogaeum Perigaeum of the Sunne should be moved every year in the same order and with the same velocity with which the Aequinoctiall points are moved and their distance from them should allwayes be the quadrant of a circle which seems to be otherwise For Astronomers say that the Aequinoxes are now the one about 28 degrees gone back from the first Star of Aries the other as much from the beginning of Libra So that the Apogaeum of the Sunne or the Aphelium of the Earth ought to be about the 28th degree of Cancer but it is reckoned to be in the 7th degree Seeing therefore we have not sufficient evidence of the 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 that so it is it is in vaine to seek for the 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 why it is so Wherefore as long as the motion of the Apogaeum is not observable by reason of the slownesse thereof and as long as it remaiues doubtful whether their distance from the Aequinoctiall points be more or lesse then a quadrant precisely so long it may be lawfull for me to thinke they proceed both of them with equall velocity Also I doe not at all meddle with the causes of the Excentricities of Saturne Jupiter Mars and Mercury Neverthelesse seeing the Excentricity of the Earth may as I have shewne be caused by the unlike constitution of the several parts of the Earth which are alternately turned towards the Sunne it is credible also that like effects may be produced in these other Planets from their having their Superficies of unlike parts And this is all I shall say concerning Sidereal Philosophy And though the causes I have here supposed be not the true causes of these Phaenomena yet I have demonstrated that they are sufficient to produce them according to what I at first propounded CHAP. XXVII Of Light Heat and of Colours 1 Of the immense Magnitude of some Bodies and the unspeakable Littleness of others 2 Of the cause of the Light of the Sun 3 How Light heateth 4 The generation of Fire from the Sunne 5 The generation of Fire from Collision 6 The cause of Light in Glow-wormes Rotten Wood and the Bolonian Stone 7 The cause of Light in the concussion of Sea-water 8 The cause of Flame Sparks and Colliquation 9 The cause why wet Hay sometimes burns of its own accord Also the cause of Lightning 10 The cause of the force of Gunpowder and what is to be ascribed to the Coals what to the Brimstone and what to the Nitre 11 How Heat is caused by Attrition 12 The distinction of Light into First Second c. 13 The causes of the Colours we see in looking through a Prisma of Glass namely of Red Yellow Blue and Violet Colour 14 Why the Moon and the Starres appear redder in the Horizon then in
But in the mean time the hard particles which are mingled with the Aire and are agitated as I have supposed with Simple Motion wil not pass through the water of the clouds but be more straightly compressed within their cavities And this I have demonstrated at the 4th and 5th Articles of the 22th Chapter Besides seeing the Globe of the Earth floateth in the Aire which is agitated by the Sunnes Motion the parts of the Aire resisted by the Earth will spread themselves every way upon the Earths Superficies as I have shewn at the 8th Article of the 21th Chapter 5 We perceive a Body to be Hard from this that when touching it we would thrust forwards that part of the same which we touch we cannot do it otherwise then by thrusting forwards the whole Body We may indeed easily and sensibly thrust forwards any particle of the Aire or Water which we touch whilst yet the rest of its parts remain to sense unmoved But we cannot do so to any part of a stone Wherfore I define a Hard Body to be that whereof no part can be sensibly moved unless the whole be moved Whatsoever therefore is Soft or Fluid the same can never be made Hard but by such motion as makes many of the parts together stop the motion of some one part by resisting the same 6 These things premised I shall shew a possible cause why there is greater Cold neer the Poles of the Earth then further from them The motion of the Sunne between the Tropicks driving the Aire towards that part of the Earths Superficies which is perpendicularly under it makes it spread it self every way and the velocity of this expansion of the Aire grows greater and greater as the Superficies of the Earth comes to be more and more straightned that is to say as the Circles which are parallel to the Aequator come to be less and less Wherefore this expansive motion of the Aire drives before it the parts of the Aire which are in its way continually towards the Poles more and more strongly as its force comes to be more and more united that is to say as the Circles which are parallel to the Aequator are less and less that is so much the more by how much they are neerer to the Poles of the Earth In those places therefore which are neerer to the Poles there is greater Cold then in those which are more remote from them Now this expansion of the Aire upon the Superficies of the Earth from East to West doth by reason of the Sunnes perpetual accession to the places which are successively under it make it Cold at the time of the Sunnes Rising and Setting but as the Sunne comes to be continually more and more perpendicular to those cooled places so by the Heat which is generated by the supervening Simple Motion of the Sunn that Cold is again remitted and can never be great because the action by the which it was generated is not permanent Wherefore I have rendred a possible cause of Cold in those places that are neer the Poles or where the obliquity of the Sunne is great 7 How Water may be congeled by Cold may be explained in this manner Let A in the first figure represent the Sunne and B the Earth A will therefore be much greater then B. Let EF be in the plain of the Equinoctial to which let GH IK and LC be parallel Lastly let C and D be the Poles of the Earth The Aire therefore by its action in those parallels will rake the Superficies of the Earth and that with motion so much the stronger by how much the parallel Circles towards the Poles grow less and less From whence must arise a Wind which will force together the uppermost parts of the water and withal raise them a little weakning their endeavour towards the Center of the Earth And from their endeavour towards the center of the Earth joyned with the endeavour of the said Wind the uppermost parts of the water will be pressed together and coagulated that is to say the top of the water will be skinned over and hardned And so againe the Water next the top will be hardned in the same manner till at length the Ice be thick And this Ice being now compacted of little hard Bodies must also containe many particles of ayre received into it As Rivers and Seas so also in the same manner may the Clouds be frozen For when by the ascending and descending of severall Clouds at the same time the Air intercepted between them is by compression forced out it rakes by little little hardens them And though those smal drops which usually make Clouds be not yet united into greater Bodies yet the same Wind will be made by it as water is congeled into Ice so will Vapours in the same manner be congeled into Snow From the same cause it is that Ice may be made by art and that not farre from the fire For it is done by the mingling of Snow and Salt together and by burying in it a small vessell full of Water Now while the Snow and Salt which have in them a great deale of aire are melting the aire which is pressed out every way in Wind rakes the sides of the Vessel and as the Wind by its motion rakes the Vessell so the Vessell by the same motion and action congeles the Water within it We find by experience that Cold is allwayes more Remisse in places where it raynes or where the weather is cloudy things being alike in all other respects then where the aire is cleare And this agreeth very well with what I have sayd before For in cleare weather the course of the Wind which as I sayd even now rakes the Superficies of the Earth as it is free from all interruption so also it is very strong But when small drops of water are either rising or falling that Wind is repelled broken and dissipated by them and the lesse the Wind is the lesse is the Cold. We find also by experience that in deep Wells the Water freezeth not so much as it doth upon the Superficies of the Earth For the Wind by which Ice is made entring into the Earth by reason of the laxity of its parts more or lesse loseth some of its force though not much So that if the Well be not deep it will freeze whereas if it be so deep as that the Wind which causeth cold cannot reach it it will not freeze We find moreover by experience that Ice is lighter then Water The cause whereof is manifest from that which I have already shewn namely that Aire is received in and mingled with the particles of the Water whilest it is in congeling 8 We have seen one way of making things Hard namely by Congelation Another way is thus Having already supposed that innumerable Atomes some harder then others and that have several simple motions of their own are intermingled with the aethereal substance
not a sufficient cause of their future Motion there being no other cause of Motion but Motion The cause therefore of such Restitution is in the parts of the Steel it self Wherefore whilest it remains bent there is in the parts of which it consisteth some motion though invisible that is to say some endeavour at least that way by which the restitution is to be made and therefore this endeavour of all the parts together is the first beginning of Restitution so that the impediment being removed that is to say the force by which it was held bent it will be restored again Now the motion of the parts by which this is done is that which I called Simple Motion or Motion returning into it self When therefore in the bending of a plate the ends are drawn together there is on one side a mutual compression of the parts which compression is one endeavour opposite to another endeavour and on the other side a divulsion of the parts The endeavour therefore of the parts on one side tends to the restitution of the plate from the middle towards the ends and on the other side from the ends towards the middle Wherefore the impediment being taken away this endeavour which is the beginning of restitution will restore the plate to its former posture And thus I have given a possible cause why some Bodies when they are bent Restore themselves again which was to be done As for Stones seeing they are made by the accretion of many very hard particles within the Earth which particles have no great coherence that is to say touch one another in small latitude and consequently admit many particles of aire it must needs be that in bending of them their internal parts will not easily be compressed by reason of their hardness And because their coherence is not firm as soon as the external hard particles are disjoyned the aethereal parts will necessarily break out and so the Body will suddenly be broken 13 Those Bodies are called Diaphanous upon which whilest the Beams of a lucid Body do work the action of every one of those Beams is propagated in them in such manner as that they still retain the same order amongst themselves or the inversion of that order and therefore Bodies which are perfectly Diaphanous are also perfectly homogeneous On the contrary an Opacous Body is that which by reason of its heterogeneous nature doth by innumerable reflexions and refractions in particles of different figures and unequal hardness weaken the Beams that fall upon it before they reach the Eie And of Diaphanous Bodies some are made such by Nature from the beginning as the substance of the Aire and of the Water and perhaps also some parts of Stones unless these also be Water that has been long congeled Others are made so by the power of Heat which congregates homogeneons Bodies But such as are made Diaphanous in this manner consist of parts which were formerly Diaphanous 14 In what manner Clouds are made by the motion of the Sunne elevating the particles of Water from the Sea and other moist places hath been explained in the 26th Chapter Also how Clouds come to be frozen hath been shewn above at the 7th Article Now from this that Aire may be enclosed as it were in Caverns and pent together more and more by the meeting of ascending and descending Clouds may be deduced a possible Cause of Thunder and Lightening For seeing the Aire consists of two parts the one Aethereal which has no proper motion of its own as being a thing divisible into the least parts the other Hard namely consisting of many hard Atomes which have every one of them a very swift simple motion of its own whilest the Clouds by their meeting do more and more straighten such Cavities as they intercept the Aethereal parts will penetrate and pass through their watry substance but the hard parts will in the mean time be the more thrust together and press one another and consequently by reason of their vehement motions they will have an endeavour to rebound from each other Whensoever therefore the compression is great enough and the concave parts of the Clouds are for the cause I have already given congeled into Ice the Cloud wil necessarily be broken this breaking of the Cloud produceth the first clap of Thunder Afterwards the Aire which was pent in having now broken through makes a concussion of the Aire without and from hence proceeds the roaring and murmur which follows and both the first Clap and the Murmur that follows it make that noise which is called Thunder Also from the same Aire breaking through the Clouds and with concussion falling upon the Eie proceeds that action upon our Eie which causeth in us a perception of that Light which we call Lightening Wherefore I have given a possible cause of Thunder and Lightening 15 But if the Vapours which are raised into Clouds do run together again into Water or be congeled into Ice from whence is it seeing both Ice and Water are heavy that they are sustained in the Aire Or rather what may the cause be that being once elevated they fall down again For there is no doubt but the same force which could carry up that Water could also sustain it there Why therefore being once carried up doth it fall again I say it proceeds from the same Simple Motion of the Sunne both that Vapours are forced to ascend and that Water gathered into Clouds is forced to descend For in the 21th Chapter and 11th Article I have shewn how Vapours are elevated and in the same Chapter and 5th Article I have also shewn how by the same motion Homogeneous Bodies are congregated Heterogeneous dissipated that is to say how such things as have a like nature to that of the Earth are driven towards the Earth that is to say what is the cause of the descent of Heavy Bodies Now if the action of the Sun be hindered in the raising of vapours and be not at all hindered in the casting of them down the Water will descend But a Cloud cannot hinder the action of the Sunne in making things of an earthly nature descend to the Earth though it may hinder it in making Vapours ascend For the lower part of a thick Cloud is so covered by its upper part as that it cannot receive that action of the Sunne by which Vapours are carried up because Vapours are raised by the perpetual fermentation of the Aire or by the separating of its smallest parts from one another which is much weaker when a thick Cloud is interposed then when the Skie is cleere And therefore whensoever a Cloud is made thick enough the water which would not descend before will then descend unless it be kept up by the agitation of the Winde Wherefore I have rendred a possible cause both why the Clouds may be sustained in the Aire and also why they may fall down again to the Earth which was propounded to
be done 16 Granting that the Clouds may be frozen it is no wonder if the Moon have been seen eclipsed at such time as she hath been almost two degrees above the Horizon the Sunne at the same time appearing in the Horizon for such an Eclipse was observed by Mestline at Tubing in the year 1590. For it might happen that a frozen Cloud was then interposed between the Sunne and the Eie of the Observer And if it were so the Sunne which was then almost two Degrees below the Horizon might appear to be in it by reason of the passing of his Beams through the Ice And it is to be noted that those that attribute such refractions to the Atmosphere cannot attribute to it so great a refraction as this Wherefore not the Atmosphere but either Water in a continued Body or else Ice must be the cause of that refraction 17 Again granting that there may be Ice in the Clouds it will be no longer a wonder that many Sunnes have sometimes appeared at once For Looking-glasses may be so placed as by reflections to shew the same object in many places And may not so many frozen Clouds serve for so many Looking-glasses and may they not be fitly disposed for that purpose Besides the number of Appearances may be encreased by refractions also and therefore it would be a greater wonder to me if such Phaenomena as these should never happen And were it not for that one Phaenomenon of the new Starre which was seen in Cassiopaea I should think Comets were made in the same manner namely by Vapours drawn not onely from the Earth but from the rest of the Planets also and congeled into one continued Body For I could very well from hence give a reason both of their Haire and of their motions But seeing that Starre remained sixteen whole moneths in the same place amongst the fixed Starres I cannot believe the matter of it was Ice Wherefore I leave to others the disquisition of the cause of Comets concerning which nothing that hath hitherto been published 〈…〉 the bare Histories of them is worth considering 18 The Heads of Rivers may be deduced from Rain-water or from melted Snowes very easily but from other causes very hardly or not at all For both Rain-water and melted Snowes run down the descents of Mountains and if they descend onely by the outward Superficies the Showres or Snowes themselves may be accounted the Springs or Fountains but if they enter the Earth descend within it then wheresoever they break out there are their Springs And as these Spings make small streams so many small streams running together make Rivers Now there was never any Spring foūd but where the Water w ch flowed to it was either further or at least as farre from the center of the Earth as the Spring it self And whereas it has bin objected by a great Philosopher that in the top of Mount-Cenis which parts Savoy from Piemont there Springs a River which runs down by Susa it is not true For there are above that River for two miles length very high hils on both sides which are almost perpetually covered with Snow from which innumerable little streams running down do manifestly supply that River with water sufficient for its magnitude CHAP. XXIX Of Sound Odour Savour and Touch 1 The definition of Sound and the distinctions of Sounds 2 The cause of the degrees of Sounds 3 The difference between Sounds Acute and Grave 4 The difference between Clear and Hoarse Sounds whence 5 The Sound of Thunder and of a Gunne whence it proceeds 6 Whence it is that Pipes by blowing into them have a clear Sound 7 Of Reflected Sound 8 From whence it is that Sound is Uniform and Lasting 9 How Sound may be helped aud hindered by the Wind. 10 Not onely Aire but other Bodies how hard soever they be conveigh Sound 11 The causes of Grave and Acute Sounds and of Concent 12 Phaenomena for Smelling 13 The first Organ and the generation of Smelling 14 How it is helped by Heat and by Wind. 15 Why such Bodies are least smelt which have least intermixture of Aire in them 16 Why Odorous things become more Odorous by being bruised 17 The first Organ of Tasting and why some Savours cause Nauseousness 18 The first Organ of Feeling and how we come to the knowledge of such Objects as are common to the Touch and other Senses SOUND is Sense generated by the action of the Medium when its motion reacheth the Eare and the rest of the Organs of Sense Now the motion of the Medium is not the Sound it self but the cause of it For the Phantasme which is made in us that is to say the Reaction of the Organ is properly that which we call Sound The principal distinctions of Sounds are these First that one Sound is stronger another Weaker Secondly that one is more Grave another more Acute Thirdly that one is Clear another Hoarse Fourthly that one is Primary another Derivative Fifthly that one is Uniform another not Sixthly that one is more Durable another less Durable Of all which distinctions the members may be subdistinguished into parts distinguishable almost infinitely For the variety of Sounds seems to be not much less then that of Colours As Vision so Hearing is generated by the motion of the Medium but not in the same manner For Sight is from Pressure that is from an Endeavour in which there is no perceptible progression of any of the parts of the Medium but one part urging or thrusting on an other propagateth that action successively to any distance whatsoever whereas the motion of the Medium by which Sound is made is a Stroke For when we Hear the Drumme of the Eare which is the first Organ of Hearing is stricken and the Drumme being stricken the Pia Mater is also shaken and with it the Arteries which are inserted into it by which the action being propagated to the Heart it self by the reaction of the Heart a Phantasm is made which we call Sound and because the reaction tendeth outwards we think it is without 2 And seeing the effects produced by Motion are greater or lesse not onely when the Velocity is greater or less but also when the Body hath greater or less Magnitude though the Velocity be the same a Sound may be greater or lesse both these wayes And because neither the greatest nor the least Magnitude or Velocity can be given it may happen that either the motion may be of so small velocity or the Body it self of so small magnitude as to produce no Sound at all or either of them may be so great as to take away the Faculty of Sense by hurting the Organ From hence may be deduced possible causes of the strength and weakness of Sounds in the following Phaenomena The first whereof is this That if a man speak through a Trunk which hath on end applyed to the mouth of the Speaker and the other to the eare of the
in all Concussion a reciprocation of Motion forwards and backwards in the parts stricken for opposite motions cannot extinguish one another in an instant as I have shewn in the 11th Art of the 8th Chap. it follows necessarily that the Sound will both continue and grow weaker and weaker till at last the action of the reciprocating aire grow so weak as to be unperceptible Wherefore a possible cause is given both of the first fierce Noyse of the Thunder and also of the Murmur that follows it The cause of the great Sound from a discharged piece of Ordnance is like that of a Clap of Thunder For the Gunpowder being fired doth in its endeavour to go out attempt every way the sides of the metal in such manner as that it enlargeth the Circumference all along and withall shortneth the axis so that whilest the peece of Ordnance is in discharging it is made both wider and shorter then it was before and therefore also presently after it is discharged its wideness will be diminished and its length encreased again by the restitution of all the particles of the matter of which it consisteth to their former position And this is done with such motion of the parts as are not onely very vehement but also opposite to one another which motions being communicated to the Aire make impression upon the Organ and by the reaction of the Organ create a Sound which lasteth for some time as I have already shewn in this Article I note by the way as not belonging to this place that the possible cause why a Gun recoyles when it is shot off may be this That being first swoln by the force of the fire and afterwards restoring it self from this restitution there proceeds an endeavour from all the sides towards the cavity and consequently this endeavour is in those parts which are next the breech which being not hollow but solid the effect of the restitution is by it hindered and diverted into the length and by this means both the breech and the whole Gun is thrust backwards and the more forcibly by how much the force is greater by which the part next the breech is restored to its former posture that is to say by how much the thiner is that part The cause therefore why Gunnes recoyle some more some less is the difference of their thickness towards the breech the greater that thickness is the less they recoyl and contrarily 6 Also the cause why the Sound of a Pipe which is made by blowing into it is nevertheless Clear is the same with that of the Sound which is made by collision For if the breath when it is blown into a Pipe doe onely rake its concave Superficies or fall upon it with a very sharp angle of incidence the Sound will not be Clear but Hoarse But if the angle be great enough the percussion which is made against one of the hollow sides will be reverberated to the opposite side and so successive repercussions will be made from side to side till at last the whole concave Superficies of the Pipe be put into motion which motion will be reciprocated as it is in Collision and this reciprocation being propagated to the Organ from the reaction of the Organ will arise a Cleare Sound such as is made by Collision or by breaking asunder of hard Bodies In the same manner it is with the Sound of a Mans voice For when the breath passeth out without interruption and doth but lightly touch the cavities through which it is sent the Sound it maketh is a Hoarse Sound But if in going out it strike strongly upon the Larinx then a Clear Sound is made as in a Pipe And the same breath as it comes in divers manners to the Palate the Tongue the Lips the Teeth and other Organs of Speech so the Sounds into which it is articulated become different from one another 7 I call that Primary Sound which is generated by motion from the sounding Body to the Organ in a straight line without reflexion and I call that Reflected Sound which is generated by one or more reflexions being the same with that we call Echo and is iterated as often as there are reflexions made from the Object to the Eare. And these reflexions are made by Hils Wals and other resisting Bodies so placed as that they make more or fewer reflexions of the motion according as they are themselves more or fewer in number and they make them more or less frequently according as they are more or less distant from one another Now the cause of both these things is to be sought for in the situation of the reflecting Bodies as is usually done in Sight For the Lawes of Reflexion are the same in both namely that the Angles of Incidence and Reflexion be equal to one another If therefore in a hollow Elliptique Body whose inside is well polished or in two right Parabolical Solids which are joyned together by one common base there be placed a Sounding Body in one of the Burning Points the Ear in the other there will be heard a Sound by many degrees greater then in the open Aire and both this and the burning of such combustible things as being put in the same places are set on fire by the Sun-beams are effects of one and the same cause But as when the visible Object is placed in one of the Burning Points it is not distinctly seen in the other because every part of the Object being seen in every line which is reflected from the Concave Superficies to the Eie makes a confusion in the Sight so neither is Sound heard articulately and distinctly when it comes to the Eare in all those reflected lines And this may be the reason why in Churches which have arched rooffs though they be neither Elliptical nor Parabolical yet because their figure is not much different from these the voice from the Pulpit will not be heard so articulately as it would be if there were no vaulting at all 8 Concerning the Uniformity and Duration of Sounds both which have one common cause we may observe that such Bodies as being stricken yeild an unequal or harsh Sound are very heterogeous that is to say they consist of parts which are very unlike both in figure and hardness such as are Wood Stones and others not a few When these are stricken there follows a concussion of their internal particles and a restitution of them again But they are neither moved alike nor have they the same action upon one another some of them recoyling from the stroke whilest others which have already finished their recoylings are now returning by which means they hinder and stop on another And from hence it is that their motions are not only unequal and harsh but also that their reciprocations come to be quickly extinguished Whensoever therfore this motion is propagated to the Eare the Sound it makes is Unequal and of small Duration On the contrary if a Body
of the parts of those plants made an Odorous liquour so also of aire passing through the same plants whilest they are growing are made Odorous aires And thus also it is with the Juices and Spirits which are bred in Living Creatures 16 That Odorous Bodies may be made more Odorous by Contrition proceeds from this that being broken into many parts which are all Odorous the aire which by respiration is drawn from the Object towards the Organ doth in its passage touch upon all those parts and receives their motion Now the aire toucheth the superficies onely and a Body having less superficies whilest it is whole then all its parts together have after it is reduced to powder it follows that the same Odorous Body yeildeth less Smell whilest it is whole then it will do after it is broken into smaller parts And thus much of Smels 17 The Tast follows whose generation hath this difference from that of the Sight Hearing and Smelling that by these we have Sense of remote Objects whereas we Tast nothing but what is contiguous and doth immediately touch either the Tongue or Palate or both From whence it is evident that the cuticles of the Tongue and Palate and the Nerves inserted into them are the first Organ of Tast and because from the concussion of the parts of these there followeth necessarily a concussion of the Pia Mater that the action communicated to these is propagated to the Brain and from thence to the farthest Organ namely the Heart in whose reaction consisteth the nature of Sense Now that Savours as well as Odours doe not onely move the Brain but the Stomack also as is manifest by the loathings that are caused by them both they that consider the Organ of both these Senses will not wonder at all seeing the Tongue the Palate the Nostrils have one and the same continued cuticle derived from the Dura Mater And that Effluviums have nothing to doe in the Sense of Tasting is manifest from this that there is no Tast where the Organ and the Object are not contiguous By what variety of motions the different kinds of Tasts which are innumerable may be distinguished I know not I might with others derive them from the divers figures of those Atomes of which whatsoever may be Tasted consisteth or from the diverse motions which I might by way of Supposition attribute to those Atomes conjecturing not without some likelyhood of truth that such things as tast Sweet have their particles moved with slow circular motion and their figures Spherical which makes them smooth and pleasing to the Organ that Bitter things have circular motion but vehement and their figures full of Angles by which they trouble the Organ and that Sowre things have straight and reciprocal motion and their figures long and small so that they cut and wound the Organ And in like manner I might assigne for the causes of other Tasts such several motions and figures of Atomes as might in probability seem to be the true causes But this would be to revolt from Philosophy to Divination 18 By the Touch we feel what Bodies are Cold or Hot though they be distant from us Others as Hard Soft Rough and Smooth we cannot feel unless they be contiguous The Organ of Touch is every one of those membranes which being continued from the Pia Mater are so diffused throughout the whole Body as that no part of it can be pressed but the Pia Mater is pressed together with it Whatsoever therefore presseth it is felt as Hard or Soft that is to say as more or less Hard. And as for the Sense of Rough it is nothing else but innumerable perceptions of Hard and Hard succeeding one another by short intervals both of time and place For we take notice of Rough and Smooth as also of Magnitude and Figure not onely by the Touch but also by Memory For though some things are touched in one Point yet Rough and Smooth like Quantity and Figure are not perceived but by the Flux of a Point that is to say we have no Sense of them without Time and we can have no Sense of Time without Memory CHAP. XXX Of Gravity 1 A Thick Body doth not contain more Matter unless also more Place then a Thinne 2 That the Descent of Heavy Bodies proceeds not from their own Appetite but from some Power of the Earth 3 The difference of Gravities proceedeth from the difference of the Impetus with which the Elements whereof Heavy Bodies are made do fall vpon the Earth 4 The cause of the Descent of Heavy Bodies 5 In what proportion the Descent of Heavy Bodies is accelerated 6 Why those that Dive do not when they are under Water feel the waight of the Water above them 7 The Waight of a Body that floateth is equal to the Waight of so much Water as would fill the space which the immersed part of the Body takes up within the Water 8 If a Body be Lighter then Water then how big soever that Body be it will float upon any quantity of Water how little soever 9 How Water may be lifted up and forced out of a Vessel by Air. 10 Why a Bladder is Heavier when blown full of aire then when it is empty 11 The cause of the ejection upwards of Heavy Bodies from a Wind-Gun 12 The cause of the ascent of Water in a Weather-glass 13 The cause of motion upwards in Living Creatures 14 That there is in Nature a kind of Body Heavier then Aire which nevertheless is not by Sense distinguishable from it 15 Of the cause of Magnetical vertue 1 IN the 21 Chapter I have defined Thick and Thinne as that place required so as that by Thick was signified a more Resisting Body and by Thinne a Body less Resisting following the custome of those that have before me discoursed of Refraction Now if we consider the true and vulgar signification of those words we shall find them to be Names Collective that is to say Names of Multitude as Thick to be that which takes up more parts of a space given Thinne that which contains fewer parts of the same magnitude in the same space or in a space equal to it Thick therefore is the same with Frequent as a Thick Troop And Thinne the same with Unfrequent as a Thinne Rank Thinne of Houses not that there is more matter in one place then in another equal place but a greater quantity of some named Body For there is not less matter or Body indefinitely taken in a Desert then there is in a City but fewer Houses or fewer Men. Nor is there in a Thick Rank a greater quantity of Body but a greater number of Souldiers then in a Thinne Wherefore the multitude paucity of the parts contained within the same space do constitute Density and Rarity whether those parts be separated by Vacuum or by Aire But the consideration of this is not of any great moment in Philosophy and therefore I let
it alone and pass on to the search of the causes of Gravity 2 Now we call those Bodies Heavy which unless they be hindred by some force are carried towards the center of the Earth and that by their own accord for ought we can by Sense perceive to the contrary Some Philosophers therefore have been of opinion that the Descent of Heavy Bodies proceeded from some internal Appetite by which when they were cast upwards they descended again as moved by themselves to such place as was agreeable to their nature Others thought they were attracted by the Earth To the former I cannot assent because I think I have already clearly enough demonstrated that there can be no beginning of motion but from an external moved Body and consequently that whatsoever hath motion or endeavour towards any place will alwayes move or endeavour towards that same place unless it be hindered by the reaction of some external Body Heavy Bodies therefore being once cast upwards cannot be cast down again but by external motion Besides seeing inanimate Bodies have no Appetite at all it is ridiculous to think that by their own innate Appetite they should to preserve themselves not understanding what preserves them forsake the place they are in and transferre themselves to another place whereas Man who hath both Appetite and understanding cannot for the preservation of his own life raise himselfe by leaping above three or four feet from the ground Lastly to attribute to created Bodies the power to move themselves what is it else then to say that there be creatures which have no dependance upon the Creator To the later who attribute the Descent of Heavy Bodies to the attraction of the Earth I assent But by what motion this is done hath not as yet been explained by any man I shall therefore in this place say somewhat of the manner and of the way by which the Earth by its action attracteth Heavy Bodies 3 That by the supposition of simple motion in the Sunne homogeneous Bodies are congregated and heterogeneous dissipated has already been demonstrated in the 5th Article of the 21 Chapter I have also supposed that there are intermingled with the pure Air certain little Bodies or as others call them Atomes which by reason of their extreme smalness are invisible and differing from one another in Consistence Figure Motion Magnitude from whence it comes to pass that some of them are congregated to the Earth others to other Planets and others are carried up and down in the spaces between And seeing those which are carried to the Earth differ from one another in Figure Motion and Magnitude they will fall upon the Earth some with greater others with less Impetus And seeing also that we compute the several degrees of Gravity no otherwise then by this their falling upon the Earth with greater or less Impetus it follows that we conclude those to be the more Heavy that have the greater Impetus and those to be less Heavy that have the less Impetus Our enquiry therefore must be by what means it may come to pass that of Bodies which descend from above to the Earth some are carried with greater others with less Impetus that is to say some are more Heavy then others We must also enquire by what means such Bodies as settle upon the Earth may by the Earth it self be forced to ascend 4 Let the Circle made upon the center C in the 2d figure be a great Circle in the Superficies of the Earth passing through the points A and B. Also let any Heavy Body as the stone A D be placed any where in the plain of the Aequator and let it be conceived to be cast up from A D perpendicularly or to be carried in any other line to E and supposed to rest there Therefore how much space soever the stone took up in A D so much space it takes up now in E. And because all place is supposed to be full the space A D will be filled by the aire which flows into it first from the neerest places of the Earth and afterwards successively from more remote places Upon the center C let a Circle be understood to be drawn through E and let the plain space which is between the Superficies of the Earth and that Circle be divided into plain Orbs equal and concentrique of which let that be the first which is contained by the two perimeters that pass through A D. Whilst therefore the aire which is in the first Orbe filleth the place A D the Orbe it self is made so much less and consequently its latitude is less then the straight line A D. Wherefore there will necessarily descend so much aire from the Orbe next abvoe In like manner for the same cause there will also be a descent of aire from the Orbe next above that and so by Succession from the Orbe in which the Stone is at rest in E. Either therefore the Stone it self or so much aire will descend And seeing aire is by the diurnal revolution of the Earth more easily thrust away then the Stone the aire which is in the Orbe that contains the Stone will be forced further upwards then the Stone But this without the admission of Vacuum cannot be unless so much aire descend to E from the place next above which being done the Stone will be thrust downwards By this means therefore the Stone now receives the beginning of its Descent that is to say of its Gravity Furthermore whatsoever is once moved will be moved continually as hath been shewn in the 19th Article of the 8th Chapter in the same way and with the same celerity except it be retarded or accelerated by some external Movent Now the aire which is the onely Body that is interposed between the Earth A and the stone above it E will have the same action in every point of the straight line E A which it hath in E. But it depressed the stone in E and therefore also it will depress it equally in every point of the straight line E A. Wherefore the stone will descend from E to A with accelerated motion The possible cause therefore of the Descent of Heavy Bodies under the Aequator is the Diurnal motion of the Earth And the same demonstration will serve if the stone be placed in the plain of any other Circle parallel to the Aequator But because this motion hath by reason of its greater slowness less force to thrust off the aire in the parallel Circles then in the Aequator and no force at all at the Poles it may well be thought for it is a certain consequent that Heavy Bodies descend with less and less velocity as they are more more remote from the Aequator that at the Poles themselves they wil either not descend at all or not descend by the Axis which whether it be true or false Experience must determine But it is hard to make the experiment both because the
a Syringe into the space FGB In that injection the aire but pure aire goeth with the same force out of the vessel through the injected water But as for those small Bodies which formerly I supposed to be intermingled with aire to be moved with simple motion they can not together with the oure air penetrate the water but remayning behind are necessarily thrust together into a narrower place namely into the space which is above the water FG. The motions therefore of those small Bodies will be less and less free by how much the quantity of the injected water is greater and greater so that by their motions falling upon one another the same small Bodies will mutually compress each other and have a perpetual endeavour of regayning their liberty and of depressing the water that hinders them Wherefore as soone as the orifice above is opened the water which is next it will have an endeavour to ascend and will therefore necessarily go out But it cannot go out unless at the same time there enter in as much aire and therefore both the water will go out and the aire enter in till those small Bodies which were left within the vessel have recovered their former liberty of motion that is to say till the vessel be again filled with aire and no water be left of sufficient height to stop the passage at B. Wherefore I have shewn a possible cause of this Phaenomenon namely the same with that of Thunder For as in the generation of Thunder the small Bodies enclosed within the Clouds by being too closely pent together do by their motion break the Clouds and restore themselves to their natural liberty so here also the small Bodies enclosed within the space which is above the straight line FG do by their own motion expel the water as soon as the passage is opened above And if the passage be kept stopped and these small Bodies be more vehemently compressed by the perpetual forcing in of more water they will at last break the vessel it self with great noise 10 If Aire be blown into a hollow Cylinder or into a Bladder it will encrease the waight of either of them a little as many have found by experience who with great accurateness have tried the same And it is no wonder seeing as I have supposed there are intermingled with the common aire a great number of small hard Bodies which are Heavier then the pure aire For the aethereal substance being on all sides equally agitated by the motion of the Sunne hath an equal endeavour towards all the parts of the Universe and therefore it hath no Gravity at all 11 We find also by experience that by the force of air enclosed in a hollow Canon a bullet of lead may with considerable violence be shot out of a Gunne of late invention called the Wind-Gun In the end of this Canon there are two holes with their Valves on the inside to shut them close one of them serving for the admission of aire and the other for the letting of it out Also to that end which serves for the receiving in of aire there is joyned another Canon of the same metal and bigness in which there is fitted a Rammer which is perforated and hath also a Valve opening towards the former Canon By the help of this Valve the Rammer is easily drawn back and letteth in aire from without and being often drawn back and returned again with violent strokes it forceth some part of that aire into the former Canon so long till at last the resistance of the enclosed aire is greater then the force of the stroke And by this means men think there is now a greater quantity of aire in the Canon then there was formerly though it were full before Also the aire thus forced in how much soever it be is hindered from getting out again by the foresaid Valves which the very endeavour of the aire to get out doth necessarily shut Lastly that Valve being opened which was made for the letting out of the aire it presently breaketh out with violence driveth the bullet before it with great force and velocity As for the cause of this I could easily attribute it as most men do to Condensation and think that the aire which had at the first but its ordinary degree of Rarity was afterwards by the forcing in of more aire condensed and last of all rarified again by being let out and restored to its natural liberty But I cannot imagine how the same place can be alwayes full and nevertheless contain sometimes a greater sometimes a less quantity of matter that is to say that it can be fuller then full Nor can I conceive how Fulness can of it self be an efficient cause of motion For both â—hese are impossible Wherefore we must seek out some other possible cause of this Phaenomenon Whilst therefore the Valve w ch serves for the letting in of aire is opened by the first stroke of the Rammer the aire within doth with equal force resist the entering of the aire from without so that the endeavours between the internal and external aire are opposite that is there are two opposite motions whilest the one goeth in and the other cometh out but no augmentation at all of aire within the Canon For there is driven out by the stroke as much pure aire which passeth between the Rammer and the sides of the Canon as there is forced in of aire impure by the same stroke And thus by many forcible strokes the quantity of small hard Bodies will be encreased within the Canon and their motions also will grow stronger and stronger as long as the matter of the Canon is able to endure their force by which if it be not broken it will at least be urged every way by their endeavour to free themselves and as soon as the Valve which serves to let them out is opened they will fly out with violent motion and carry with them the bullet which is in their way Wherefore I have given a possible cause of this Phaenomenon 12 Water contrary to the custome of Heavy Bodies ascendeth in the Weather-glasse but it doth it when the aire is cold for when it is warme it descendeth againe And this Organ is called a Thermometer or Thermoscope because the degrees of Heat and Cold are measured and marked by it It is made in this manner Let A B C D in the 5th figure be a vessel full of water and E F G a hollow Cylinder of glasse closed at E and open at G. Let it be heated and set upright within the water to F and let the open end reach to G. This being done as the aire by little and little grows colder the water will ascend slowly within the Cylinder from F towards E till at last the externall and internall aire coming to be both of the same temper it will neither ascend higher nor descend lower till the temper of the aire be changed Suppose it therefore
in like manner is followed by the noxious matter contained in CB by this means the pit is for that time made healthful Out of this History which I write onely to such as have had experience of the truth of it without any designe to support my Philosophy with Stories of doubtful credit may be collected the following possible cause of this Phaenomenon namely that there is a certain matter fluid most transparent and not much lighter then water which breaking out of the Earth fills the Pit to C and that in this matter as in water both Fire and Living creatures are extinguished 15 About the nature of Heavy Bodies the greatest difficulty ariseth from the contemplation of those things which make other Heavy Bodies ascend to them such are Jet Amber and the Loadstone But that which troubles men most is the Loadstone which is also called Lapis Herculeus a stone though otherwise despicable yet of so great power that it taketh up Iron from the Earth and holds it suspended in the aire as Hercules did Antaeus Nevertheless we wonder at it somewhat the less because we see Jet draw up Straws which are Heavy Bodies though not so Heavy as Iron But as for Jet it must first be excited by rubbing that is to say by motion to and fro whereas the Loadstone hath sufficient excitation from its own nature that is to say from some internal principle of motion peculiar to it self Now whatsoever is moved is moved by some contiguous and moved Body as hath been formerly demonstrated And from hence it follows evidently that the first endeavour which Iron hath towards the Loadstone is caused by the motion of that aire which is contiguous to the Iron Also that this motion is generated by the motion of the next aire and so on successively till by this succession we find that the motion of all the intermediate air taketh its beginning from some motion which is in the Loadstone it self which motion because the Loadstone seems to be at rest is invisible It is therefore certain that the attractive power of the Loadstone is nothing else but some motiō of the smallest particles thereof Supposing therefore that those small Bodies of which the Loadstone is in the bowels of the Earth composed have by nature such motion or endeavour as was above attributed to Jet namely a reciprocal motiō in a line too short to be seen both those stones wil have one the same cause of attraction Now in what manner and in what order of working this cause produceth the effect of attraction is the thing to be enquired And first we know that when the string of a Lute or Viol is stricken the Vibration that is the reciprocal motion of that string in the same straight Line causeth like Vibration in another string which has like tension We know also that the dregs or small sands which sink to the bottom of a Vessel will be raised up from the bottom by any strong and reciprocal agitation of the water stirred with the hand or with a staff Why therefore should not reciprocal motion of the parts of the Loadstone contribute as much towards the moving of Iron For if in the Loadstone there be supposed such reciprocal motion or motion of the parts forwards and backwards it will follow that the like motion will be propagated by the aire to the Iron and consequently that there will be in all the parts of the Iron the same reciprocations or motions forwards and backwards And from hence also it will follow that the intermediate aire between the Stone and the Iron will by little and little be thrust away and the aire being thrust away the Bodies of the Loadstone and the Iron will necessarily come together The possible cause therefore why the Loadstone and Jet draw to them the one Iron the other Strawes may be this that those attracting Bodies have reciprocal motion either in a straight line or in an Elliptical line when there is nothing in the nature of the attracted Bodies which is repugnant to such a motion But why the Loadstone if with the help of Cork it float at liberty upon the top of the water should from any position whatsoever so place it self in the plain of the Meridian as that the same points which at one time of its being at rest respect the Poles of the Earth should at all other times respect the same Poles the cause may be this That the reciprocal motion which I supposed to be in the parts of the Stone is made in a line parallel to the Axis of the Earth and has been in those parts ever since the Stone was generated Seeing therefore the Stone whilest it remains in the Mine and is carried about together with the Earth by its diurnal motion doth by length of time get a habit of being moved in a line which is perpendicular to the line of its reciprocal motion it will afterwards though its axis be removed from the parallel situation it had with the axis of the Earth retain its endeavour of returning to that situation again and all endeavour being the beginning of motion and nothing intervening that may hinder the same the Loadstone will therefore return to its former situation For any piece of Iron that has for a long time rested in the plain of the Meridian whensoever it is forced from that situation and afterwards left to its own liberty again will of it self return to lie in the Meridian again which return is caused by the endeavour it acquired from the diurnal motion of the Earth in the parallel circles which are perpendicular to the Meridians If Iron be rubbed by the Loadstone drawn from one Pole to the other two things will happen one that the Iron will acquire the same direction with the Loadstone that is to say that it will lie in the Meridian and have its Axis and Poles in the same position with those of the Stone the other that the like Poles of the Stone and of the Iron will avoid one another and the unlike Poles approach one another And the cause of the former may be this that Iron being touched by motion which is not reciprocal but drawn the same way from Pole to Pole there will be imprinted in the Iron also an endeavour from the same Pole to the same Pole For seeing the Loadstone differs from Iron no otherwise then as Ore from Metal there will be no repugnance at all in the Iron to receive the same motion which is in the Stone From whence it follows that seeing they are both affected alike by the diurnal motion of the Earth they will both equally return to their situation in the Meridian whensoever they are put frō the same Also of the later this may be the cause that as the Loadstone in touching the Irō doth by its action imprint in the Iron an endeavour towards one of the Poles suppose towards the North Pole so reciprocally the
Metaphysical Empusa not by skirmish but by letting in the light upon her For I am confident if any confidence of a Writing can proceed from the Writers fear circumspection diffidence that in the three former parts of this Book all that I have said is sufficiently demonstrated from Definitions all in the fourth part from Suppositions not absurd But if there appear to your Lordship any thing less fully demonstrated then to satisfie every Reader the cause was this that I professed to write not all to all but some things to Geometricians onely But that your Lordship will be satisfied J cannot doubt There remains the second Section which is concerning Man That part thereof where J handle the Optiques contayning six Chapters together with the Tables of the Figures belonging to them I have already written engravenlying by me above these six years The rest shall as soon as J can be added to it though by the contumelies petty injuries of some unskilful men I know already by experience how much greater thanks will be due then payed me for telling Men the truth of what Men are But the burthen I have taken on me I mean to carry through not striving to appease but rather to revenge my self of Envy by encreasing it For it contents me that I have your Lordships favour which being all you require J acknowledge and for which with my prayers to Almighty God for your Lordships safety J shall to my power be always thankefull London April 23 1655. YOUR LORDSHIPS most humble Servant Thomas Hobbes The Authors Epistle To the Reader THink not courteous Reader that the Philosophy the Elements whereof I am going to set in order is that which makes Philosophers Stones nor that which is found in the Metaphsique Codes But that it is the Natural Reason of Man busily flying up and down among the Creatures bringing back a true report of their Order Causes Effects Philosophy therefore the Childe of the World and your own Mind is within your self perhaps not fashioned yet but like the World its Father as it was in the beginning a thing confused Do therefore as the Statuaries do who by hewing off that which is superfluous do not make but find the Image Or imitate the Creation If you will be a Philosopher in good earnest let your Reason move upon the Deep of your own Cogitations and Experience Those things that lie in Confusion must be set asunder distinguished and every one stampt with its own name set in order that is to say your Method must resemble that of the Creation The order of the Creation was Light Distinction of Day and Night the Firmament the Luminaries Sensible Creatures Man and after the Creation the Commandement Therefore the order of Contemplation will be Reason Definition Space the Starres Sensible Quality Man and after Man is grown up Subjection to Command In the first part of this Section which is entitled Logique I set up the light of Reason In the Second which hath for title the Grounds of Philosophy I distinguish the most common Notions by accurate definition for the avoiding of confusion and obscurity The third part concerns the Expansion of Space that is Geometry The fourth contains the Motion of the Starres together with the doctrine of Sensible Qualities In the second Section if it please God shall be handled Man In the third Section the doctrine of Subjection is handled already This is the Method I followed and if it like you you may use the same for I do but propound not commend to you any thing of mine But whatsoever shall be the Method you will like I would very fain commend Philosophy to you that is to say the study of Wisdome for want of which we have all suffered much dammage lately For even they that study Wealth do it out of love to Wisdome for their Treasures serve them but for a Looking-glass wherin to behold and contemplate their owne Wisdome Nor do they that love to be employed in publike business aime at any thing but place wherein to shew their Wisdome Neither do Voluptuous men neglect Philosophy but onely because they know not how great a pleasure it is to the Mind of Man to be ravished in the vigorous and perpetual embraces of the most beauteous World Lastly though for nothing else yet because the Mind of Man is no less impatient of Empty Time then Nature is of Empty Place to the end you be not forced for want of what to do to be troublesome to men that have business or take hurt by falling into idle Company but have somewhat of your own wherewith to fill up your time I recommend unto you the Study of Philosophy Farewell T. H. The Titles of the CHAPTERS The first Part or Logique CHAP. 1 Of Philosophy CHAP. 2 Of Names CHAP. 3 Of Proportion CHAP. 4 Of Syllogisme CHAP. 5 Of Erring Falsity and Captions CHAP. 6 Of Method The Second Part or The first Grounds of Philosophy CHAP. 7 Of Place and Time CHAP. 8 Of Body and Accident CHAP. 9 Of Cause and Effect CHAP. 10 Of Power and Act. CHAP. 11 Of Identity and Difference CHAP. 12 Of Quantity CHAP. 13 Of Analogisme or the Same Proportion CHAP. 14 Of Straight and Crocked Angle and Figure The third Part Of the Proportions of Motions and Magnitudes CHAP. 15 Of the Nature Properties and divers considerations of Motion and Endeavour CHAP. 16 Of Motion Accelerated and Uniform and of Motion by Concourse CHAP. 17 Of Figures Deficient CHAP. 18 Of the Equation of Straight Lines which the Crooked Lines of Parabolas and other Figures made in imitation of Parabolas CHAP. 19 Of Angles of Incidence and Reflexion equal by supposition CHAP. 20 Of the Dimension of a Circle and the Division of Arches or Angles CHAP. 21 Of Circular Motion CHAP. 22 Of other Variety of Motions CHAP. 23 Of the Center of Equiponderation of Bodies pressing downwards in straight parallel lines CHAP. 24 Of Refraction and Reflexion The fourth Part of Physiques or the Phaenomena of Nature CHAP. 25 Of Sense and Animall Motion CHAP. 26 Of the World and of the Starres CHAP. 27 Of Light Heat and of Colours CHAP. 28 Of Cold Wind Hard Ice Restitution of Bodies bent Diaphanous Lightning and Thunder and of the Heads of Rivers CHAP. 29 Of Sound Odour Savour and Touch. CHAP. 30 Of Gravity COMPUTATION OR LOGIQUE CHAP. I. Of Philosophy 1 The Introduction 2 The Definition of Philosophy explained 3 Ratiocination of the Mind 4 Properties what they are 5 How Properties are known by Generation contrarily 6 The Scope of Philosophy 7 The Utility of it 8 The Subject 9 The Parts of it 10 The Epilogue PHILOSOPHY seems to me to be amongst men now in the same manner as Corn and Wine are said to have been in the world in ancient time For from the beginning there were Vines and Ears of Corn growing here and there in the fields but no care was taken for the
Indefinitely that is to know as much as they can without propounding to themselves any limited question or they enquire into the Cause of some determined Appearance or endeavour to find out the certainty of something in question as what is the cause of Light of Heat of Gravity of a Figure propounded and the like or in what Subiect any propounded Accident is inhaerent or what may conduce most to the generation of some propounded Effect from many Accidents or in what manner particular Causes ought to be compounded for the production of some certaine Effect Now according to this variety of things in question sometimes the Analyticall Method is to be used and sometimes the Syntheticall 4 But to those that search after Science indefinitely which consists in the knowledge of the Causes of all things as far forth as it may be attained and the Causes of Singular things are compounded of the Causes of Universall or Simple things it is necessary that they know the Causes of Universall things or of such Accidents as are common to all Bodies that is to all Matter before they can know the Causes of Singular things that is of those Accidents by which one thing is distinguished from another And againe they must know what those Universall things are before they can know their Causes Moreover seeing Universall things are contained in the Nature of Singular things the knowledge of them is to be acquired by Reason that is by Resolution For example if there be propounded a Conception or Idea of some Singular thing as of a Square this Square is to be resolved into a Plain terminated with a certaine number of equall and straight lines and right angles For by this Resolution we have these things Universall or agreeable to all Matter namely Line Plain which containes Superficies Terminated Angle Straightness Rectitude and Equality and if we can find out the Causes of these we may compound them all together into the Cause of a Square Againe if any man propound to himselfe the Conception of Gold he may by Resolving come to the Ideas of Solid Visible Heavy that is tending to the Center of the Earth or downwards and many other more Universall then Gold it selfe and these he may Resolve againe till he come to such things as are most Universall And in this manner by Resolving continually we may come to know what those things are whose Causes being first known severally and afterwards compounded bring us to the Knowledge of Singular things I conclude therefore that the Method of attaining to the Universall Knowledge of Things is purely Analyticall 5 But the Causes of Universall things of those at least that have any Cause are manifest of themselues or as they say commonly known to Nature so that they need no Method at all for they have all but one Universall Cause which is Motion For the variety of all Figures arises out of the variety of those Motions by which they are made and Motion cannot be understood to have any other Cause besides Motion nor has the Variety of those things we perceive by Sense as of Colours Sounds Savours c. any other Cause then Motion residing partly in the Objects that work upon our Senses and partly in our selves in such manner as that it is manifestly some kind of Motion though we cannot without Ratiocination come to know what kind For though many cannot understand till it be in some sort demonstrated to them that all Mutation consists in Motion yet this happens not from any obscurity in the thing it selfe for it is not intelligible that any thing can depart either from Rest or from the Motion it has except by Motion but either by having their Naturall Discourse corrupted with former Opinions received from their Masters or else for this that they do not at all bend their mind to the enquiring out of Truth 6 By the Knowledge therefore of Universalls and of their Causes which are the first Principles by which we know the 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 of things we have in the first place their Definitions which are nothing but the explication of our Simple Conceptions For example he that has a true Conception of Place cannot be ignorant of this Definition Place is that space which is possessed or filled adaequately by some Body and so he that conceives Motion aright cannot but know that Motion is the privation of one Place and the acquisition of another In the next place we have their Generations or Descriptions as for example that a Line is made by the Motion of a Point Superficies by the Motion of a Line and one Motion by another Motion c. It remains that we enquire what Motion begets such and such Effects as what Motion makes a Straight line and what a Circular what Motion thrusts what drawes and by what way what makes a thing which is seen or heard to be seen or heard sometimes in one manner sometimes in another Now the Method of this kind of Enquiry is Compositive For first we are to observe what Effect a Body moved produceth when we consider nothing in it besides its Motion and we see presently that this makes a Line or length next what the Motion of a long Body produces which we find to be Superficies and so forwards till we see what the Effects of Simple Motion are and then in like manner we are to observe what proceeds from the Addition Multiplication Substraction and Division of these Motions and what Effects what Figures and what Properties they produce from which kind of Contemplation sprung that part of Philosophy which is called Geometry From this consideration of what is produced by Simple Motion we are to passe to the consideration of what Effects one Body moved worketh upon another and because there may be Motion in all the severall parts of a Body yet so as that the whole Body remain still in the same place we must enquire first what Motion causeth such and such Motion in the whole that is when one Body invades another Body which is either at Rest or in Motion what way and with what swiftnesse the invaded Body shall move and again what Motion this second Body will generate in a third and so forwards From which Contemplation shall be drawn that part of Philosophy which treats of Motion In the Third place we must proceed to the Enquiry of such Effects as are made by the Motion of the Parts of any Body as how it comes to passe that things when they are the same yet seeme not to be the same but changed And here the things we search after are sensible Qualities such as Light Colour Transparency Opacity Sound Odour Savour Heat Cold and the like which because they cannot be known till we know the Causes of Sense it selfe therefore the consideration of the Causes of Seeing Hearing Smelling Tasting and Touching belongs to this third place and all those qualities and Changes above mentioned are to be referred to
the fourth place which two considerations comprehend that part of Philosophy which is called Physiques And in these four parts is contained whatsoever in Naturall Philosophy may be explicated by Demonstration properly so called For if a Cause were to be rendred of Natural Appearances in special as what are the Motions and Influences of the heavenly Bodies and of their parts the reason hereof must either be drawn from the parts of the Sciences above mentioned or no reason at all will be given but all left to uncertaine conjecture After Physiques we must come to Morall Philosophy in which we are to consider the Motions of the Mind namely Appetite Aversion Love Benevolence Hope Fear Anger Emulation Envy c. what Causes they have and of what they be Causes And the reason why these are to be considered after Physiques is that they have their Causes in Sense and Imagination which are the Subject of Physicall Contemplation Also the reason why all these Things are to be searched after in the order abovesaid is that Physiques cannot be understood except we know first what Motions are in the smallest parts of Bodies nor such Motion of Parts till we know what it is that makes another Body move nor this till we know what Simple Motion will effect And because all Appearance of things to sense is determined and made to be of such and such Quality and Quantity by Compounded Motions every one of which has a certaine degree of Velocity and a certaine and determined way therefore in the first place we are to search out the wayes of Motion simply in which Geometry consists next the wayes of such generated Motions as are manifest and lastly the wayes of internal and invisible Motions which is the Enquiry of Naturall Philosophers And therefore they that study Naturall Philosophy study in vaine except they begin at Geometry and such Writers or Disputers thereof as are ignorant of Geometry do but make their Readers and Hearers lose their time 7 Civill and Morall Philosophy doe not so adhere to one another but that they may be severed For the Causes of the Motions of the Mind are known not onely by Ratiocination but also by the Experience of every man that takes the paines to observe those Motions within himselfe And therefore not only they that have attained the knowledge of the Passions and Perturbations of the Mind by the Syntheticall Method and from the very first Principles of Philosophy may by proceeding in the same way come to the Causes and Necessity of constituting Common-wealths and to get the Knowledge of what is Naturall Right and what are Civill Duties and in every kind of Government what are the Rights of the Commonwealth and all other Knowledge appertaining to Civill Philosophy for this reason that the Principles of the Politiques consist in the Knowledge of the Motions of the Mind and the Knowledge of these Motions from the knowledge of Sense and Imagination but even they also that have not learned the first part of Philosophy namely Geometry and Physiques may notwithstanding attain the Principles of Civill Philosophy by the Analyticall Method For if a Question be propounded as Whether such an Action be Just or Uniust if that Uniust be resolved into Fact against Law and that notion of Law into the Command of him or them that have Coercive Power and that Power be derived from the Wills of Men that constitute such Power to the end they may live in Peace they may at last come to this that the Appetites of Men and the Passions of their Minds are such that unlesse they be restrained by some Power they will alwayes be making warre upon one another which may be known to be so by any mans experience that will but examine his owne Mind And therefore from hence he may proceed by Compounding to the determination of the Justice or Injustice of any propounded Action So that it is manifest by what has been said that the Method of Philosophy to such as seek Science simply without propounding to themselves the Solution of any Particular question is partly Analyticall and partly Syntheticall namely that which proceeds from Sense to the invention of Principles Analyticall and the rest Syntheticall 8 To those that seek the Cause of some certaine and pro pounded Appearance or Effect it happens sometimes that they know not whether the thing whose Cause is sought after be Matter or Body or some Accident of a Body For though in Geometry when the Cause is sought of Magnitude or Proportion or Figure it be certainly known that these things namely Magnitude Proportion and Figure are Accidents yet in Naturall Philosophy where all questions are concerning the Causes of the Phantasmes of sensible things it is not so easie to discern between the things themselves from which those Phantasmes proceed and the Appearances of those things to the sense which have deceived many especially when the Phantasmes have been made by Light For Example a Man that looks upon the Sunne has a certaine shining Idea of â—â—e Magnitude of about a foâ—t over and this he calls the Sunne thougâ—…e know the Sunne to be truly a great deale bigger and in like 〈…〉 the Phantasme of the same thing appears sometimes â—â—und by being 〈…〉 a â—arre off and sometimes square by being neerer Whereupon â—t may well be doubted whether that Phantasme be Maâ—… or some Body Naturall or onely some Accident of a Body in the examination of which doubt we may use this Method The Properties of Matter and Accidents already found out by Us by the Syntheticall Method from their Definitions are to be compared with the Idea we have before us and if it agree with the Properties of Matter or Body then it is a Body otherwise it is an Accident Seeing therefore Matter cannot by any endeavour of ours be either Made or Destroyed or Encreased or Diminished or Moved out of its place whereas that Idea Appeares Vanishes is Encreased and Diminished and Moved hither and thither at pleasure we may certainly conclude that it is not a Body but an Accident onely And this Method is Syntheticall 9 But if there be a doubt made concerning the Subject of any known Accident for this may be doubted sometimes as in the praecedent example doubt may be made in what Subject that Splendor and apparent Magnitude of the Sunne is then our enquiry must proceed in this manner First Matter in Generall must be divided into parts as into Object Medium and the Sentient it selfe or such other parts as seem most conformable to the thing propounded Next these parts are severally to be examined how they agree with the Definition of the Subject and such of them as are not capable of that Accident are to be rejected For example If by any true Ratiocination the Sunne be found to be greater then its apparent Magnitude then that Magnitude is not in the Sunne If the Sunne be in one determined straight line and one determined
distance and the Magnitude and Splendor be seen in more lines and distances then one as it is in Reflection or Refraction then neither that Splendor nor apparent Magnitude are in the Sun it self and therefore the Body of the Sun cannot be the Subject of that Splendor and Magnitude And for the same reasons the Aire and other parts will be rejected till at last nothing remain which can be the Subject of that Splendor and Magnitude but the Sentient it selfe And this Method in regard the Subject is divided into parts is Analitycall and in regard the Properties both of the Subject and Accident are compared with the Accident concerning whose Subject the enquiry is made it is Syntheticall 10 But when we seek after the Cause of any propounded Effect we must in the first place get into our Mind an exact Notion or Idea of that which we call Cause namely that A Cause is the Summe or Aggregate of all such Accidents both in the Agents and the Patient as concurre to the producing of the Effect propounded all which existing together it cannot be understood but that the Effect existeth with them or that it cannot possibly exist if any one of them be absent This being known in the next place we must examine singly every Accident that accompanies or praecedes the Effect as farre forth as it seemes to conduce in any manner to the production of the same and see whether the propounded Effect may be conceived to exist without the existence of any of those Accidents and by this meanes separate such Accidents as do not concurre from such as concurre to produce the said Effect which being done we are to put together the concurring Accidents and consider whether we can possibly conceive that when these are all present the Effect propounded will not follow and if it be evident that the Effect will follow then that Aggregate of Accidents is the entire Cause otherwise not but we must still search out and put together other Accidents For example if the Cause of Light be propounded to be sought out first we examine things without us and find that whensoever Light appeares there is some principall Object as it were the fountaine of Light without which we cannot have any perception of Light and therefore the concurrence of that Object is necessary to the generation of Light Next we consider the Medium and find that unlesse it be disposed in a certaine manner namely that it be transparent though the Object remain the same yet the Effect will not follow and therefore the concurrence of Transparency is also necessary to the generation of Light Thirdly we observe our own Body and find that by the indisposition of the Eyes the Brain the Nerves and the Heart that is by Obstructions Stupidity and Debility we are deprived of Light so that a fitting disposition of the Organs to receive impressions from without is likewise a necessary part of the Cause of Light Again of all the Accidents inhaerent in the Object there is none that can conduce to the effecting of Light but onely Action or a certain Motion which cannot be conceived to be wanting whensoever the Effect is present for that any thing may shine it is not requisite that it be of such or such â—agnitude or Figure or that the whole Body of it be moved out of the place it is in unlesse it may perhaps be said that in the Sun or other Body that which causeth Light is the light it hath in it selfe which yet is but a trifling exception seeing nothing is meant thereby but the Cause of Light as if any man should say that the Cause of Light is that in the Sunne which produceth it it remaines therefore that the Action by which Light is generated is Motion only in the parts of the Object Which being understood we may easily conceive what it is the Medium contributes namely the continuation of that Motion to the Eye and lastly what the Eye and the rest of the Organs of the Sentient contribute namely the continuation of the same Motion to the last Organ of Sense the Heart And in this manner the Cause of Light may be made up of Motion continued from the Original of the same Motion to the Original of Vitall Motion Light being nothing but the alteration of Vitall Motion made by the impression upon it of Motion continued from the Object But I give this onely for an example for I shall speak more at large of Light and the generation of it in its proper place In the mean time it is manifest that in the searching out of Causes there is need partly of the Analyticall and partly of the Syntheticall Method of the Analyticall to conceive how circumstances conduce severally to the production of Effects and of the Syntheticall for the adding together and compounding of what they can effect singly by themselves And thus much may serve for the Method of Invention It remaines that I speake of the Method of Teaching that is of Demonstration and of the Meanes by which we demonstrate 11 In the Method of Invention the use of words consists in this that they may serve for Marks by which whatsoever we have found out may be recalled to memory for without this all our Inventions perish nor will it be possible for us to go on from Principles beyond a Syllogisme or two by reason of the weaknesse of Memory For example if any man by considering a Triangle set before him should find that all its angles together taken are equall to two right angles and that by thinking of the same tacitely without any use of words either understood or expressed and it should happen afterwards that another Triangle unlike the former or the same in different scituation should be offered to his consideration he would not know readily whether the same property were in this last or no but would be forced as often as a different Triangle were brought before him and the difference of Triangles is infinite to begin his contemplation anew which he would have no need to do if he had the use of Names for every Universal Name denotes the conceptions we have of infinite Singular things Neverthelesse as I said above they serve as Markes for the helpe of our Memory whereby we register to our selves our own Inventions but not as Signes by which we declare the same to others so that a man may be a Philosopher alone by himselfe without any Master Adam had this capacity But to Teach that is to Demonstrate supposes two at the least and Syllogisticall Speech 12 And seeing Teaching is nothing but leading the Mind of him we teach to the knowledge of our Inventions in that Track by which we attained the same with our own Mind therefore the same Method that served for our Invention will serve also for Demonstration to others saving that we omit the first part of Method which proceeded from the Sense of Things to Universal Principles which
not upon our Thought we say is a thing subsisting of itself as also existing because without Us and lastly it is called the Subject because it is so placed in and subjected to Imaginary Space that it may be understood by Reason as well as perceived by Sense The Definition therefore of Body may be this A BODY is that which having no dependance upon our Thought is coincident or coextended with some part of Space 2 But what an Accident is cannot so easily be explained by any Definition as by Examples Let us imagine therefore that a Body fills any Space or is coextended with it that Coextention is not the coextended Body And in like manner let us imagine that the same Body is removed out of its place that Removing is not the removed Body Or let us think the same not removed that notremoving or Rest is not the resting Body What then are these things They are Accidents of that Body But the thing in question is What is an Accident which is an Enquiry after that which we know already and not that which we should enquire after For who does not alwayes and in the same manner understand him that sayes any thing is Extended or Moved or not Moved But most men will have it be said that an Accident is something namely some part of a natural thing when indeed it is no part of the same To satisfie these men as well as may be they answer best that define an Accident to be the Manner by which any Body is conceived which is all one as if they should say An Accident is that faculty of any Body by which it works in us a Conception of itself Which Definition though it be not an Answer to the Question propounded yet it is an Answer to that Question which should have been propounded namely whence does it happen that one part of any Body appears here another part there For this is well answered thus It happens from the Extension of that Body Or How comes it to pass that the whole Body by succession is seen now here now there and the answer will be By reason of its Motion Or lastly Whence is it that any Body possesseth the same space for sometime And the answer will be because it is not moved For if concerning the Name of a Body that is concerning a Concrete Name it be asked what is it the answer must be made by Definition for the Question is concerning the signification of the Name But if it be asked concerning an Abstract Name what is it the Cause is demanded why a thing appears so or so As if it be asked what is Hard The Answer will be Hard is that whereof no Part gives place but when the Whole gives place But if it be demanded what is Hardness A Cause must be shewn why a Part does not give place except the Whole give place Wherefore I define an ACCIDENT to be the Maâ—ner of our conception of Body 3 When an Accident is said to be in a Body it is not so to be understood as if any thing were conteined in that Body as if for example Redness were in Blood in the same manner as Blood is in a bloody cloth that is as a Part in the Whole for so an Accident would be a Body also But as Magnitude or Rest or Motion is in that which is Great or which Resteth or which is Moved which how it is to be understood every man understands so also it is to be understood that every other Accident is in its Subject And this also is explicated by Aristotle no otherwise then negatively namely that An Accident is in its Subject not as any part thereof but so as that it may be away the Subject still remaining which is right saving that there are certain Accidents which can never perish except the Body perish also for no Body can be conceived to be without Extension or without Figure All other Accidents which are not common to all Bodies but peculiar to some onely as To be at Rest to be Moved Colour Hardness and the like do perish continually and are succeeded by others yet so as that the Body never perisheth And as for the opinion that some may have that all other Accidents are not in their Bodies in the same manner that Extension Motion Rest or Figure are in the same for example that Colour Heat Odour Vertue Vice and the like are otherwise in them and as they say inherent I desire they would suspend their judgement for the present and expect a little till it be found out by Ratiocination whether these very Accidents are not also certain Motions either of the Mind of the perceiver or of the Bodies themselves which are perceived for in the search of this a great part of Naturall Philosophy consists 4 The Extension of a Body is the same thing with the MAGNITUDE of it or that which some call Real Space But this Magnitude does not depend upon our Cogitation as Imaginary Space doth for this is an Effect of our Imagination but Magnitude is the Cause of it this is an Accident of the Mind that of a Body existing out of the Mind 5 That Space by which word I here understand Imaginary Space which is coincident with the Magnitude of any Body is called the PLACE of that Body and the Body it self is that which we call the Thing Placed Now Place and the Magnitude of the Thing Placed differ First in this that a Body keeps alwayes the same Magnitude both when it is at Rest and when it is Moved but when it is Moved it does not keep the same Place Secondly in this that Place is a Phantasme of any Body of such and such Quantity and Figure but Magnitude is the peculiar Accident of every Body for one Body may at several times have several Places but has always one and the same Magnitude Thirdly in this that Place is nothing out of the Mind nor Magnitude any thing within it And lastly Place is feigned Extension but Magnitude true Extension and a Placed Body is not Extension but a Thing Extended Besides Place is Immoveable for seeing that which is Moved is understood to be carried from Place to Place if Place were Moved it would also be carried from Place to Place so that one Place must have another Place and that Place another Place and so on infinitely which is ridiculous And as for those that by making Place to be of the same Nature with Real Space would from thence maintain it to be Immoveable they also make Place though they do not perceive they make it so to be a meer Phantasme For whilest One affirms that Place is therefore said to be Immoveable because Space in general is considered there if he had remembred that nothing is General or Universal besides Names or Signes he would easily have seen that that Space which he sayes is considered in general is nothing but a Phantasme in the Mind or
that the Proportion of the first Antecedent to the first Consequent is the same with that of the second Antecedent to the second Consequent And when four Magnitudes are thus to one another in Geometrical Proportion they are called Proportionals and by some more briefly Analogisme And Greater Proportion is the Proportion of a Greater Antecedent to the same Consequent or of the same Antecâ—dent to a Less Consequent and when the Proportion of the first Antecedent to the first Consequent is greater then that of the second Antecedent to the second Consequent the four Magnitudes which are so to one another may be called Hyperlogisme Less Proportion is the Proportion of a Less Antecedent to the same Consequent or of the same Antecedent to a Greater Consequent and when the Proportion of the first Antecedent to the first Consequent is less then that of the second to the second the four Magnitudes may be called Hypologisme 5 One Arithmetical Proportion is the Same with another Arithmetical Proportion when one of the Antecedents exceeds its Consequent or is exceeded by it as much as the other Antecedent exceeds its Consequent or is exceeded by it And therefore in four Magnitudes Arithmetically Proportional the sum of the Extremes is equal to the sum of the Means For if A. B C. D be Arithmetically Proportional and the Difference on both sides be the same Excess or the same Defect E then B+C if A be greater then B will be equal to A − E+C and A+D will be equal to A+C − E But A − E+C and A+C − E are equal Or if A be less then B then B+C will be equal to A+E+C and A+D will be equal to A+C+E But A+E+C and A+C+E are equal Also if there be never so many Magnitudes Arithmetically Proportional the Sum of them all will be equal to the Product of half the number of the Terms multiplyed by the Sum of the Extremes For if A. B C. D E. F be Arithmetically Proportional the Couples A+F B+E C+D will be equal to one another and their Sum will be equal to A+F multiplyed by the number of their Combinations that is by half the number of the Terms If of four Unequal Magnitudes any two together taken be equal to the other two together taken then the greatest and the least of them will be in the same Combination Let the Unequal Magnitudes be A B C D and let A+B be equal to C+D let A be the greatest of them all I say B will be the least For if it may be let any of the rest as D be the least Seeing therefore A is greater then C and B then D A+B will be greater then C+D which is contrary to what was supposed If there be any four Magnitudes the Sum of the greatest and least the Sum of the Means the difference of the two greatest and the difference of the two least will be Arithmetically Proportional For let there be four Magnitudes whereof A is the greatest D the least and B and C the Means I say A+D B+C A − B. C − D are Arithmetically Proportional For the difference between the first Antecedent and its Consequent is this A+D − B − C and the difference between the second Antecedent and its Consequent this A − B − C+D but these two Differences are equal and therefore by this 5th Article A+D B+C A − B. C − D are Arithmetically Proportional If of four Magnitudes two be equal to the other two they will be in reciprocal Arithmetical Proportion For let A+B be equal to C+D I say A. C D. B are Arithmetically Proportional For if they be not let A. C D. E supposing E to be greater or less then B be Arithmetically Proportional and then A+E will be equal to C+D wherefore A+B and C+D are not equal which is contrary to what was supposed 6 One Geometrical Proportion is the same with another Geometrical Proportion when the same Cause producing equal Effects in equal Times determines both the Proportions If a Point Uniformly moved describe two Lines either with the same or different Velocity all the parts of them which are contemporary that is which are described in the same time will be Two to Two in Geometrical Proportion whether the Antecedents be taken in the same Line or not For from the point A in the 10 Figure at the end of the 14 Chapter let the two Lines A D A G be described with Uniform Motion and let there be taken in them two parts AB AE and again two other parts AC AF in such manner that AB AE be contemporary and likewise AC AF contemporary I say first taking the Antecedents AB AC in the Line AD and the Consequents AE AF in the Line AG that AB AC AE AF are Proportionals For seeing by the 8th Chapter and the 15 Article Velocity is Motion considered as determined by a certain Length or Line in a certain Time transmitted by it the quantity of the Line AB will be determined by the Velocity and Time by which the same AB is described and for the same reason the quantity of the Line AC will be determined by the Velocity and Time by which the same AC is described and therefore the proportion of AB to AC whether it be Proportion of Equality or of Excess or Defect is determined by the Velocities and Times by which AB AC are described But seeing the Motion of the Point A upon AB and AC is Uniform they are both desribed with equal Velocity and therefore whether one of them have to the other the Proportion of Majority or of Minority the sole cause of that Proportion is the difference of their Times and by the same reason it is evident that the proportion of AE to AF is determined by the difference of their Times onely Seeing therefore AB AE as also AC AF are contemporary the difference of the Times in which AB and AC are described is the same with that in which AE and AF are described Wherfore the proportion of AB to AC and the proportion of AE to AF are both determined by the same Cause But the Cause which so determines the proportion of both works equally in equal Times for it is Uniform Motion and therefore by the last precedent Definition the proportion of AB to AC is the same with that of AE to AF and consequently AB AC AF. AF are Proportionals which is the first Secondly taking the Antecedents in different Lines I say AB AE AC AF are Proportionals For seeing AB AE are described in the same Time the difference of the Velocities in which they are described are the sole Cause of the proportion they have to one another And the same may be said of the proportion of AC to AF. But seeing both the Lines AD and AG are passed over by Uniform Motion the difference of the Velocities in which AB AE are described will be the same with the
drawn parallel to BD in the points where they cut the Line BEFC But all the parallels to BD as RE SF AC and the rest that can possibly be drawn from the Line AB to the Line BEFC make the Area of the Plain ABEFC and all the parallels to the same BD as QF OE DB the rest drawn to the points where they cut the same Line BEFC make the Area of the Plain BEFCD As therefore the aggregate of the Swiftnesses wherwith the Plain BEFCD is described is to the aggregate of the Swiftnesses wherewith the Plain ACFEB is described so is the Plain it self BEFCD to the Plain it self ACFEB But the aggregate of the Times represented by the parallels AB GE HF and the rest maketh also the Area ACFEB And therefore as the aggregate of all the Lines QF OE DB and all the rest of the Lines parallel to BD and terminated in the Line BEFC is to the aggregate of all the Lines HF GE AB and all the rest of the Lines parallel to CD terminated in the same Line BEFC that is as the aggregate of the Lines of Swiftness to the aggregate of the lines of Time or as the whole Swiftness in the parallels to DB to the whole Time in the parallels to CD so is the Plain BEFCD to the Plain ACFEB And the proportions of QF to FH and of OE to EG and of DB to BA and so of all the rest taken together are the proportion of the Plain DBEFC to the Plain ABEFC But the Lines QF OE DB and the rest are the Lines that designe the Swifness and the Lines HF GE AB the rest are the Lines that designe the Times of the motions and therefore the proportion of the Plain DBEFC to the Plain ABEFC is the proportions of all the Velocities taken together to all the Times taken together Wherefore as the proportions of the Swiftnesses c. which was to be demonstrated The same holds also in the diminution of the Circles whereof the lines of Time are the Semidiameters as may easily be conceived by imagining the whole Plain ABCD turned round upon the Axis BD for the Line BEFC will be every where in the Superficies so made and the Lines HG GE AB which here are Parallelograms will be there Cylinders the Diameters of whose bases are the lines HF GE AB c. and the Altitude a point that is to say a quantity less then any quantity that can possibly be named and the Lines QF OE DB c. small solids whose lengths and breadths are less then any quantity that can be named But this is to be noted that unless the proportion of the summe of the Swiftnesses to the proportion of the summe of the Times be determined the proportion of the Figure DBEFC to the Figure ABEFC cannot be determined Thirdly I define RESISTANCE to be the endeavour of one moved Body either wholly or in part contrary to the endeavour of another moved Body which toucheth the same I say wholly contrary when the endeavour of two Bodies proceeds in the same straight Line from the opposite extremes and contrary in part when two Bodies have their endeavour in two Lines which proceeding from the extreme points of a straight Line meet without the same Fourthly that I may define what it is to PRESSE I say that Of two moved Bodies one Presses the other when with its Endeavour it makes either all or part of the other Body to go out of its place Fifthly A Body which is pressed and not wholly removed is said to RESTORE it self when the pressing Body being taken away the parts which were moved do by reason of the internal constitution of the pressed Body return every one into its own place And this we may observe in Springs in blown Bladders and in many other Bodies whose parts yeild more or less to the Endeavour which the pressing Body makes at the first arrival but afterwards when the pressing Body is removed they do by some force within them Restore themselves and give their whole Body the same figure it had before Sixthly I define FORCE to be the Impetus or Quickness of Motion multiplyed either into it self or into the Magnitude of the Movent by means wherof the said Movent works more or less upon the Body that resists it 3 Having premised thus much I shal now demonstrate First That if a point moved come to touch another point which is at rest how little soever the Impetus or quickness of its motion be it shall move that other point For if by that Impetus it do not at all move it out of its place neither shall it move it with double the same Impetus for nothing doubled is still nothing and for the same reason it shall never move it with that Impetus how many times soever it be multiplyed because nothing how soever it be multiplyed will for ever be nothing Wherefore when a point is at rest if it do not yeild to the least Impetus it will yeild to none and consequently it will be impossible that that which is at rest should ever be moved Secondly that when a point moved how little soever the Impetus thereof be falls upon a point of any Body at rest how hard soever that Body be it will at the first touch make it yeild a little For if it do not yeild to the Impetus which is in that point neither will it yeild to the Impetus of never so many points which have all their Impetus severally equal to the Impetus of that point For seeing all those points together work equally if any one of them have no effect the aggregate of them all together shall have no effect as many times told as there are points in the whole Body that is still no effect at all and by consequent there would be some Bodies so hard that it would be impossible to break them that is a finite hardnesse or a finite force would not yeild to that which is infinite which is absurd Corollary It is therefore manifest that Rest does nothing at all nor is of any efficacy and that nothing but Motion gives Motion to such things as be at Rest and takes it from things moved Thirdly that Cessation in the Movent does not cause Cessation in that which was moved by it For by the 11th Number of the 1 Article of this Chapter whatsoever is moved persevers in the same way with the same Swiftness as long as it is not hindered by some thing that is moved against it Now it is manifest that Cessation is not contrary Motion and therefore it follows that the standing still of the Movent does not make it necessary that the thing moved should also stand still Corollary They are therefore deceived that reckon the taking away of the impediment or resistance for one of the causes of Motion 4 Motion is brought into account for divers respects First as in a Body Undivided that
which it is inscribed so that the Complement of the Spiral that is that space in the Circle which is without the Spiral Line is double to the space within the Spiral Line In the same manner if there be taken a mean proportional every where between the Semidiameter of the Circle which contains the Spiral and that part of the Semidiameter which is within the same there will be made another figure which will be half the Circle And to conclude this Rule serves for all such Spaces as may be described by a Line or Superficies decreasing either in magnitude or power so that if the proportions in which they decrease be commensurable to the proportions of the times in which they decrease the magnitudes of the figures they describe will be known 12 The truth of that proposition which I demonstrated in the second Article which is the foundation of all that has been said concerning Deficient Figures may be derived from the Elements of Philosophy as having iâ—â— original in this That all equality and inequality between two effects that is all Proportion proceeds from and is determined by the equal and unequal causes of those effects or from the proportion which the causes concurring to one effect have to the causes which concurre to the producing of the other effect and that therefore the proportions of Quantities are the same with the proportions of their causes Seeing therefore two Deficient Figures of which one is the Complement of the other are made one by motion decreasing in a certain time and proportion the other by the loss of Motion in the same time the causes which make and determine the quantities of both the figures so that they can be no other then they are differ onely in this that the proportions by which the quantity which generates the figure proceeds in describing of the same that is the proportions of the remainders of all the times and altitudes may be other proportions then those by which the same generating quantity decreases in making the Complement of that Figure that is the proportions of the quantity which generates the Figure continually diminished Wherefore as the proportions of the quantity in which Motion is lost is to that of the decreasing quantities by which the Deficient Figure is generated so will the Defect or Complement be to the Figure it self which is generated 13 There are also other quantities which are determinable from the knowledge of their causes namely from the comparison of the Motions by which they are made and that more easily then from the common Elements of Geometry For example That the Superficies of any portion of a Sphere is equal to that Circle whose Radius is a straight Line drawn from the Pole of the portion to the Circumference of its base I may demonstrate in this manner Let B A C in the 7 Figure be a portion of a Sphere whose Axis is A E whose base is B C let A B be the straight line drawn from the Pole A to the base in B and let A D equal to A B touch the great Circle B A C in the Pole A. It is to be proved that the Circle made by the Radius A D is equal to the Superficies of the portion B A C. Let the plain A E B D be understood to make a revolution about the Axis A E it is manifest that by the straight line A D a Circle will be described and by the arch A B the Superficies of a portion of a Sphere and lastly by the Subtense A B the Superficies of a right Cone Now seeing both the straight line A B and the arch A B make one and the same revolution and both of them have the same extreme points A and B the cause why the the Spherical Superficies which is made by the arch is greater then the Conical Superficies which is made by the Subtense is that A B the arch is greater then A B the Subtense and the cause why it is greater consists in this that although they be both drawn from A to B yet the Subtense is drawn straight but the arch angularly namely according to that angle which the arch makes with the Subtense which angle is equal to the angle D A B for an angle of contingence adds nothing to an angle of a Segment as has been shewn in the 14 Chapter at the 16th Article Wherefore the magnitude of the angle D A B is the cause why the Superficies of the portion described by the arch A B is greater then the Superficies of the right Cone described by the Subtense A B. Again the cause why the Circle described by the Tangent A D is greater then the Superficies of the right Cone described by the Subtense A B notwitstanding that the Tangent and the Subtense are equal and both moved round in the same time is this that A D stands at right angles to the Axis but A B obliquely which obliquity consists in the same angle D A B. Seeing therefore the quantity of the angle D A B is that which makes the excess both of the Superficies of the Portion and of the Circle made by the Radius A D above the superficies of the Right Cone described by the subtense A B it follows that both the Superficies of the Portion and that of the Circle do equally exceed the Superficies of the Cone Wherefore the Circle made by A D or A B and the Spherical Superficies made by the arch A B are equal to one another which was to be proved â—4 If these Deficient Figures which I have described in a 〈◊〉 were capable of exact description then any number of mean proportionals might be found out between two straight lines given For example in the Parallelogram A B C D in the 8th Figure let the three-sided figure of two Means be described which many call a Cubical Parabola and let R and S be two given straight lines between which if it be required to find two mean proportionals it may be done thus Let it be as R to S so B C to B F and let F E be drawn parallel to B A and cut the crooked line in E then through E let G H be drawn parallel and equal to the straight line A D and cut the Diagonal B D in I for thus we have G I the greatest of two Means between G H and G E as appears by the description of the figure in the 4th Article Wherefore if it be as G H to G I so R to another line T that T will be the greatest of two Means between R and S. And therefore if it be again as R to T so T to another line X that will be done which was required In the same manner four mean proportionals may be found out by the description of a three-sided figure of four Means and so any other number of Means c. CHAP. XVIII Of the Equation of Straight Lines with the
uniformly the Straight line P C. Seeing therefore the two Straight lines A P and P C are described in the time A E with the same encrease of Impetus wherewith the Crooked line A B C is described in the same time A E that is seeing the Line A P C and the Line A B C are transmitted by the same Body in the same Time with equal Velocities the Lines themselves are equal which was to be demonstrated By the same method if any of the Semiparabolasters in the Table of the 3d Article of the precedent Chapter be exhibited may be found a Straight line equal to the Crooked line thereof namely by dividing the Diameter into two equal parts and proceeding as before Yet no man hitherto hath compared any Crooked with any Straight Line though many Geometricians of every Age have endeavoured it But the cause why they have not done it may be this that there being in Euclide no Definition of Equality nor any mark by which to judge of it besides Congruity which is the 8th Axiome of the first Book of his Elements a thing of no use at all in the comparing of Straight and Crooked and others after Euclide except Archimedes and Apollonius and in our time Boâ—aâ—entura thinking the industry of the Ancients had reached to all that was to be done in Geometry thought also that all that could be propounded was either to be deduced from what they had written or else that it was not at all to be done It was therefore disputed by some of those Ancients themselves whether there might be any Equality at all between Crooked and Straight Lines Which question Archimedes who assumed that some Straight lineâ— was equal to the Circumference of a Circle seems to have despised as he had reason And there is a late Writer that granteth that between a Straight and a Crooked Line there is Equality but now now sayes he since the fall of Adam without the special assistance of Divine Grace it is not to be found CHAP. XIX Of Angles of Incidence and Reflection equal by supposition 1 If two straight lines falling upon another straight line be parallel the lines reflected from them shall also be parallel 2 If two straight lines drawn from one point fall upon another straight line the lines reflected from them if they be drawn out the other way will meâ—t in an angle equal to the angle made by the lines of Incidence 3 If two straight parallel lines drawn not oppositely but from the same parts fall upon the Circumference of a Circle the lines reflected from them if produced they meet within the Circle will make an angle double to that which is made by two straight lines drawn from the Center to the points of Incidence 4 If two straight lines drawn from the same point without a Circle fall upon the Circumference and the lines reflected from them being produced meet within the Circle they will make an angle equal to twice that angle which is made by two straight lines drawn from the Center to the points of Incidence together with the angle which the incident lines themselves make 5 If two straight lines drawn from one point fall upon the concave Circumference of a Circle and the angle they make be less then twice the angle at the Center the lines reflected from them and meeting within the Circle will make an angle which being added to the angle of the incident lines will be equal to twice the angle at the Center 6 If through any one point two unequal Chords be drawn cutting one another and the Center of the Circle be not placed between them and the lines reflected from them concurre wheresoever there cannot through the point through which the two former lines were drawn be drawn any other straight line whose reflected line shall pass through the common point of the two former lines reflected 7 In equal Chords the same is not true 8 Two points being given in the Circumference of a Circle to draw two straight lines to them so as that their reflected lines may contain any angle given 9 If a straight line falling upon the Circumference of a Circle be produced till it reach the Semidiameter and that part of it which is intercepted between the Circumference and the Semidiameter be equal to that part of the Semidiameter which is between the point of concourse the center the reflected line will be parallel to the Semidiameter 10 If from a point within a Circle two straight lines be drawn to the Circumference and their reflected lines meet in the Circumference of the same Circle the angle made by the reflected lines will be a third part of the angle made by the incident lines WHether a Body falling upon the superficies of another Body and being reflected from it do make equal angles at that superficies it belongs not to this place to dispute being a knowledge which depends upon the natural causes of Reflection of which hitherto nothing has been said but shall be spoken of hereafter In this place therefore let it be supposed that the angle of Incidence is equal to the angle of Reflection that our present search may be applyed not to the finding out of the causes but some consequences of the same I call an Angle of Incidence that which is made between a straight line and another line straight or crooked upon which it falls and which I call the Line Reflecting and an Angle of Reflection equal to it that which is made at the same point between the straight line which is reflected and the line reflecting 1 If two straight lines which fall upon another straight line be be parallel their reflected lines shall be also parallel Let the two straight lines AB and CD in the 1 figure which fall upon the straight line EF at the points B and D be parallel and let the lines reflected from them be BG and DH I say BG and DH are also parallel For the angles ABE and CDE are equal by reason of the parallellelisme of AB and CD and the angles GBF and HDF are equal to them by supposition for the lines BG and DH are reflected from the lines AB and CD Wherefore BG and DH are parallel 2 If two straight lines drawn from the same point fall upon another straight line the lines reflected from them if they be drawn out the other way will meet in an angle equal to the angle of the Incident lines From the point AC in the 2d figure let the two straight lines AB and AD be drawn and let them fall upon the straight line EK at the points B and D and let the lines BI and DG be reflected from them I say IB and GD do converge and that if they be produced on the other side of the line EK they shall meet as in F and that the angle BFD shal be equal to the angle BAD For the angle of Reflection IBK is equal to the angle
the supposed hardness and therefore the other must needs be namely that the Body come neerer to A. Wherefore the Body at I has greater endeavour towards the center A when its hard side is next it then when it is averted from it But the Body in I while it is moving in the circumference of the Circle IB has sometimes one side sometimes another turned towards the center and therefore it is sometimes neerer sometimes further off from the center A. Wherefore the Body at I is not carried in the circumference of a perfect Circle which was to be demonstrated CHAP. XXII Of other Variety of Motion 1 Endeavour and Pressure how they differ 2 Two kinds of Mediums in which Bodies are moved 3 Propagation of Motion what it is 4 What motion Bodies have when they press one another 5 Fluid Bodies when they are pressed together penetrate one another 6 When one Body presseth another and doth not penetrate it the action of the pressing Body is perpendicular to the Superficies of the Body pressed 7 When a hard Body pressing another Body penetrates the same it doth not penetrate it perpendicularly unless it fall perpendicularly upon it 8 Motion sometimes opposite to that of the Movent 9 In a full Medium Motion is propagated to any distance 10 Dilatation and Contraction what they are 11 Dilatation and Contraction suppose Mutation of the smallest parts in respect of their situation 12 All Traction is Pulsion 13 Such things as being pressed or bent restore themselves have motion in their internal parts 14 Though that which carrieth another be stopped the Body carried will proceed 15 16 The effects of Percussion not to be compared with those of Waight 17 18 Motion cannot begin first in the internal parts of a Body 19 Action and Reaction proceed in the same Line 20 Habit what it is 1 I Have already in the 15th Chap. at the 2d Article defined Endeavour to be Motion through some Length though not considered as Length but as a Point Whether therefore there be resistance or no resistance the Endeavour will still be the same For simply to Endeavour is to Go. But when two Bodies having opposite Endeavours press one another then the Endeavour of either of them is that which we call Pressure and is mutual when their pressures are opposite 2. Bodies moved and also the Mediums in which they are moved are of two kinds For either they have their parts coherent in such manner as no part of the Moved Body will easily yeild to the Mouent except the whole Body yeild also and such are the things we call Hard Or else their parts while the whole remains unmoved will easily yeild to the Movent and these we call Fluid or Soft Bodies For the words Fluid Soft Tough and Hard in the same manner as Great and Little are used onely comparatively and are not different kinds but different degrees of Quality 3 To Do and to Suffer is to Move and to be moved and nothing is moved but by that which toucheth it and is also moved as has been formerly shewn And how great sover the distance be we say the first Movent moveth the last moved Body but mediately namely so as that the first moveth the second the second the third and so on till the last of all be touched When therefore one Body having opposite Endeavour to another Body moveth the same and that moveth a third and so on I call that action Propagation of Motion 4 When two fluid Bodies which are in a free and open Space press one another their parts will endeavour or be moved towards the sides not onely those parts which are there where the mutual contact is but all the other parts For in the first contact the parts which are pressed by both the endeavouring Bodies have no place either forwards or backwards in which they can be moved and therefore they are pressed out towards the sides And this expressure when the forces are equal is in a line perpendicular to the Bodies pressing But whensoever the formost parts of both the Bodies are pressed the hindermost also must be pressed at the same time for the motion of the hindermost parts cannot in an instant be stopped by the resistance of the formost parts but proceeds for some time and therefore seeing they must have some place in which they may be moved and that there is no place at all for them forwards it is necessary that they be moved into the places which are towards the sides every way And this effect followes of necessity not onely in Fluid but in Consistent and Hard Bodies though it be not alwayes manifest to sense For though from the compression of two stones we cannot with our eyes discerne any swelling outwards towards the sides as we perceive in two Bodies of wax yet we know well enough by reason that some tumor must needs be there though it be but little 5 But when the Space is enclosed and both the Bodies be fluid they will if they be pressed together penetrate one anoteer though differently according to their different endeavours For suppose a hollow Cylinder of hard matter well stopped at both ends but filled first below with some heavy fluid Body as Quicksilver and above with Water or Aire If now the bottome of the Cylinder be turned upwards the heaviest fluid Body which is now at the top having the greatest endeavour downwards and being by the hard sides of the vessel hindered from extending it selfe sidewayes must of necessity either be received by the lighter Body that it may sink through it or else it must open a passage through it selfe by which the lighter Body may ascend For of the two Bodies that whose parts are most easily separated will the first be divided which being done it is not necessary that the parts of the other suffer any separation at all And therefore when two Liquours which are enclosed in the same vessel change their places there is no need that their smallest parts should be mingled with one another for a way being opened through one of them the parts of the other need not be separated Now if a fluid Body which is not enclosed press a hard Body its endeavour will indeed be towards the internal parts of that hard Body but being excluded by the resistance of it the parts of the fluid Body will be moved every way according to the Superficies of the hard Body and that equally if the pressure be perpendicular for when all the parts of the Cause are equal the Effects will be equal also But if the pressure be not perpendicular then the angles of Incidence being unequal the expansion also will be unequal namely greater on that side where the angle is greater because that motion is most direct which proceeds by the directest Line 6 If a Body pressing another Body do not penetrate it it will nevertheless give to the part it presseth an endeavour to yeild and recede
nothing but perturbed Light is comprehended Wherefore the Phantasme of a Lucid Body is Light and of a coloured Body Colour But the Object of Sight properly so called is neither Light nor Colour but the Body itself which is lucid or enlightned or coloured For Light and Colour being Phantasmes of the Sentient cannot be Accidents of the Object Which is manifest enough from this that Visible things appear oftentimes in places in which we know assuredly they are not and that in different places they are of different colours and may at one and the same time appear in divers places Motion Rest Magnitude and Figure are common both to the Sight and Touch and the whole appearance together of Figure and Light or Colour is by the Greeks commonly called 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 and by the Latines Species and Imago all which names signifie no more but Appearance The phantasme which is made by Hearing is Sound by Smell Odour by Tast Savour and by Touch Hardness and Softness Heat and Cold Wetness Oiliness and many more which are easier to be distinguished by sense then words Smoothness Roughness Rarity and Density refer to Figure and are therefore common both to Touch and Sight And as for the Objects of Hearing Smel Tast and Touch they are not Sound Odour Savour Hardness c. but the Bodies themselves from which Sound Odour Savour Hardness c. proceed Of the causes of which and of the manner how they are produced I shall speak hereafter But these Phantasmes though they be effects in the Sentient as Subject produced by Objects working upon the Organs yet there are also other effects besides these produced by the same Objects in the same Organs namely certain Motions proceeding from Sense which are called Animal Motions For seeing in all Sense of external things there is mutual Action and Reaction that is two Endeavours opposing one another it is manifest that the motion of both of them together will be continued every way especially to the confines of both the Bodies And when this happens in the internal Organ the Endeavour outwards will proceed in a solid Angle which will be greater and consequently the Idea greater then it would have been if the impression had been weaker 11 From hence the Natural cause is manifest First why those things seem to be greater which caeteris paribus are seen in a greater Angle Secondly why in a serene cold night when the Moon doth not shine more of the fixed Stars appear then at another time For their action is less hindred by the serenity of the Aire and not obscured by the greater Light of the Moon which is then absent and the Cold making the Air more pressing helpeth or strengtheneth the action of the Stars upon our Eies in so much as Stars may then be seen which are seen at no other time And this may suffice to be said in general concerning Sense made by the Reaction of the Organ For as for the place of the Image the deceptions of Sight and other things of which we have experience in our selves by Sense being they depend for the most part upon the Fabrick it self of the Eie of Man I shall speak of them then when I come to speak of Man 12 But there is another kind of Sense of which I will say somthing in this place namely the Sense of Pleasure and Pain proceeding not from the Reaction of the Heart outwards but from continual action from the outermost part of the Organ towards the Heart For the original of Life being in the Heart that motion in the Sentient which is propagated to the Heart must necessarily make some alteration or diversion of Vital Motion namely by quickning or slackening helping or hindering the same Now when it helpeth it is Pleasure and when it hindereth it is Pain Trouble Grief c. And as Phantasmes seem to be without by reason of the Endeavour outwards so Pleasure and Pain by reason of the Endeavour of the Organ inwards seem to be within namely there where the first Cause of the Pleasure or Pain is as when the Pain proceeds from a Wound we think the Pain and the Wound are both in the same place Now Vital Motion is the Motion of the Bloud perpetually circulating as hath been shewn from many infallible signes and marks by Doctor Harvey the first Observer of it in the Veins and Arteries Which Motion when it is hindered by some other Motion made by the action of sensible Objects may be restored again either by bending or setting straight the parts of the Body which is done when the Spirits are carried now into these now into other Nerves till the Pain as farre as is possible be quite taken away But if Vital Motion be helped by Motion made by Sense then the parts of the Organ will be disposed to guide the Spirits in such manner as conduceth most to the preservation and augmentation of that motion by the help of the Nerves And in animal motion this is the very first Endeavour and found even in the Embrio which while it is in the wombe moveth its limbes with voluntary motion for the avoiding of whatsoever troubleth it or for the pursuing of what pleaseth it And this first Endeavour when it tends towards such things as are known by experience to be pleasant is called APPETITE that is an Approaching and when it shuns what is troublesome AVERSION or Flying from it And little Infants at the beginning and as soon as they are born have appetite to very few things as also they avoid very few by reason of their want of Experience and Memory therefore they have not so great a variety of animal Motion as we see in those that are more grown For it is not possible without such knowledge as is derived from Sense that is without Experience and Memory to know what will prove pleasant or hurtful onely there is some place for conjecture from the looks or aspects of things And hence it is that though they do not know what may do them good or harm yet sometimes they approach and sometimes retire from the same thing as their doubt prompts them But afterwards by accustoming themselves by little and little they come to know readily what is to be pursued and what to be avoided and also to have a ready use of their Nerves and other Organs in the pursuing and avoiding of good and bad Wherefore Appetite and Aversion are the first Endeavours of Animal Motion Consequent to this first Endeavour is the Impulsion into the Nerves and Retraction again of Animal Spirits of which it is necessary there be some Receptacle on place neer the original of the Nerves and this Motion or Endeavour is followed by a swelling and Relaxation of the Muscles and lastly these are followed by Contraction and Extension of the limbes which is Animal Motion 13 The Considerations of Appetites and Aversions are divers For seeing Living Creatures have sometimes Appetite and
sometimes Aversion to the same thing as they think it will either be for their good or their hurt while that vicissitude of Appetites and Aversions remains in them they have that series of Thoughts which is called DELIBERATION which lasteth as long as they have it in their power to obtain that which pleaseth or to avoid that which displeaseth them Appetite therefore and Aversion are simply so called as long as they follow not Deliberation But if Deliberation have gone before then the last act of it if it be Appetite is called WILL if Aversion UNWILLINGNESSE so that the same thing is called both Will and Appetite but the consideration of them namely before and after Deliberation is divers Nor is that which is done within a Man whilest he Willeth any thing different from that which is done in other living Creatures whilest Deliberation having preceded they have Appetite Neither is the freedome of Willing or not willing greater in Man then in other living Creatures For where there is Appetite the entire cause of Appetite hath preceded and consequently the act of Appetite could not choose but follow that is hath of necessity followed as is shewn Chapt. 9th Article 5. And therefore such a Liberty as is free from Necessity is not to be found in the Will either of Men or Beasts But if by Liberty we understand the faculty or power not of Willing but of Doing what they Will then certainly that Liberty is to be allowed to both and both may equally have it whensover it is to be had Again when Appetite and Aversion do with celerity succeed one another the whole series made by them hath its name sometimes from one sometimes from the other For the same Deliberation whilest it inclines sometimes to one sometimes to the other is from Appetite called HOPE and from Aversion FEAR For where there is no Hope it is not to be called Fear but HATE and where no Fear not Hope but DESIRE To conclude all the Passions called Passions of the Minde consist of Appetite and Aversion except pure Pleasure and Pain which are a certain Fruition of good or Evil as Anger is Aversion from some imminent evil but such as is joyned with Appetite of avoiding that evil by force But because the Passions and Perturbations of the Minde are innumerable and many of them not to be discerned in any Creatures besides Men I will speak of them more at large in that Section which is concerning Man As for those Objects if there be any such which do not at all stir the Mind we are said to Contemn them And thus much of Sense in general In the next place I shall speak of Sensible Objects CHAP. XXVI Of the World and of the Starres 1 The Magnitude and Duration of the World inscrutable 2 No place in the World Empty 3 The arguments of Lucretius for Vacuum invalid 4 Other arguments for the establishing of Vacuum invalid 5 Six suppositions for the salving of the Phaenomena of Nature 6 Possible causes of the Motions Annual and Diurnal and of the apparent Direction Station and Retrogradation of the Planets 7 The supposition of Simple Motion why likely 8 The cause of the Excentricity of the annual motion of the Earth 9 The cause why the Moon hath alwayes one and the same face turned towards the Earth 10 The cause of the Tides of the Ocean 11 The cause of the Praecession of the Equinoxes 1 COnsequent to the Contemplation of Sense is the contemplation of Bodies which are the efficient causes or Objects of Sense Now every Object is either a part of the whole World or an Aggregate of parts The greatest of all Bodies or sensible Objects is the World it self which we behold when we look round about us from this point of the same which we call the Earth Concerning the World as it is one Aggregate of many parts the things that fall under inquiry are but few and those we can determine none Of the whole World we may inquire what is its Magnitude what its Duration and how many there be but nothing else For as for Place and Time that is to say Magnitude and Duration they are only our own fancies of a Body simply so called that is to say of a Body indefinitely taken as I have shewne before in the 7 chapter All other Phantasmes are of Bodies or Objects as they are distinguished from one another as Colour the Phantasme of coloured Bodies Sound of Bodies that move the Sense of Hearing c. The questions concerning the Magnitude of the World are whether it be Finite or Infinite Full or not Full Concerning its Duration whether it had a Beginning or be Eternall and concerning the number whether there be One or Many though as concerning the Number if it were of infinite Magnitude there could be no controversy at all Also if it had a beginning then by what Cause and of what Matter it was made and againe from whence that Cause and that Matter had their being will be new questions till at last we come to one or many eternall Cause or Causes And the determination of all these things belongeth to him that professeth the universal doctrine of Philosophy in case as much could be known as can be sought But the knowledge of what is Infinite can never be attained by a finite Inquirer Whatsoever we know that are Men we learn it from our Phantasmes and of Infinite whether Magnitude or Time there is no Phantasme at all so that it is impossible either for a man or any other creature to have any conception of Infinite And though a man may from some Effect proceed to the immediate Cause thereof frō that to a more remote Cause and so ascend continually by right ratiocination from Cause to Cause yet he will not be able to proceed eternally but wearied will at last give over without knowing whether it were possible for him to proceed to an end or not But whether we suppose the World to be Finite or Infinite no absurdity will follow For the same things which now appear might appear whether the Creator had pleased it should be Finite or Infinite Besides though from this that nothing can move it self it may rightly be inferred that there was some first eternal Movent yet it can never be inferred though some use to make such inference that that Movent was eternally Immoveable but rather eternally Moved For as it is true that nothing is moved by it self so it is true also that nothing is moved but by that which is already moved The questions therefore about the Magnitude and Beginning of the World are not to be determined by Philosophers but by those that are lawfully authorised to order the Worship of God For as Almighty God when he had brought his People into Judaea allowed the Priests the first fruits reserved to himself so when he had delivered up the World to the disputations of Men it was his pleasure that
will remain no cause at all why the water should be forced out Wherefore the assertion of Vacuum is repugnant to the very experiment which is here brought to establish it Many other Phaenomena are usually brought for Vacuum as those of Weather-glasses Aeolipiles Wind-guns c. Which would all be very hard to be salved unless water be penetrable by aire without the intermixture of empty space But now seeing aire may with no great endeavour pass through not onely water but any other fluid Body though never so stubborn as Quicksilver these Phaenomena prove nothing Nevertheless it might in reason be expected that he that would take away Vacuum should without Vacuum shew us such causes of these Phaenomena as should be at least of equal if not greater probability This therefore shall be done in the following discourse when I come to speak of these Phaenomena in their proper places But first the most general Hypotheses of natural Philosophy are to be premised And seeing that Suppositions are put for the true Causes of apparent Effects every Supposition except such as be absurd must of necessity consist of some supposed possible Motion for Rest can never be the Essicient Cause of any thing Motion supposeth Bodies Moveable of which there are three kinds Fluid Consistent and mixt of both Fluid are those whose parts may by very weak endeavonr be separated from one another and Consistent those for the separation of whose parts greater force is to be applyed There are therefore degrees of Consistency which degrees by comparison with more or less Consistent have the names of Hardness or Softness Wherefore a Fluid Body is alwayes divisible into Bodies equally Fluid as Quantity into Quantities and Soft Bodies of whatsoever degree of Softness into Soft Bodies of the same degree And though many men seem to conceive no other difference of Fluidity but such as ariseth from the different magnitudes of the parts in which Sense Dust though of Diamonds may be called Fluid Yet I understand by Fluidity that which is made such by Nature equally in every part of the Fluid Body not as Dust is Fluid for so a House which is falling in pieces may be called Fluid but in such manner as Water seems Fluid and to divide it self into parts perpetually Fluid And this being well understood I come to my Suppositions 5 First therefore I suppose That the Immense Space which we call the World is the Aggregate of all Bodies which are either Consistent Visible as the Earth and the Starres or Invisible as the small Atomes which are disseminated through the whole space between the Earth and the Stars and lastly that most Fluid Aether which so fils all the rest of the Universe as that it leaves in it no empty place at all Secondly I suppose with Copernicus That the greater Bodies of the World which are both consistent and permanent have such order amongst themselves as that the Sunne hath the first place Mercury the second Venus the third The Earth with the Moon going about it the fourth Mars the fifth Jupiter with his Attendants the sixth Saturne the seventh and after these the Fixed Starres have their several distances from the Sunne Thirdly I suppose That in the Sunne the rest of the Planets there is and alwayes has been a Simple Circular Motion Fourthly I suppose That in the Body of the Aire there are certain other Bodies intermingled which are not Fluid but withal that they are so small that they are not preceptible by Sense and that these also have their proper Simple Motion and are some of them more some less hard or consistent Fifthly I suppose with Kepler That as the distance between the Sunne and the Earth is to the distance between the Moon and the Earth so the distance between the Moon and the Earth is to the Semidiameter of the Earth As for the Magnitude of the Circles and the Times in which they are described by the Bodies which are in them I will suppose them to be such as shall seem most agreeable to the Phaenomena in question 6 The causes of the different Seasons of the Year and of the several variations of Dayes and Nights in all the parts of the superficies of the Earth have been demonstrated first by Copernicus and since by Kepler Galilaeus and others from the supposition of the Earths diurnal revolution about its own Axis together with its Annual motion about the Sunne in the Ecliptick according to the order of the Signes and thirdly by the annual revolution of the same Earth about its own center contrary to the order of the Signs I suppose with Copernicus That the diurnal revolution is from the motion of the Earth by which the Aequinoctial Circle is described about it And as for the other two annual motions they are the efficient cause of the Earths being carried about in the Ecliptick in such manner as that its Axis is alwayes kept parallel to it self Which parallelisme was for this reason introduced lest by the Earths annual revolution its Poles should seem to be necessarily carried about the Sunne contrary to experience I have in the 10th Artic. of the â—â—th Chap. demonstrated from the supposition of Simple Circular Motion in the Sun that the Earth is so carried about the Sunne as that its Axis is thereby kept always parallel to it self Wherefore from these two supposed motions in the Sunne the one Simple Circular Motion the other Circular Motion about its owns Center it may be demonstrated that the Year hath both the same variations of Dayes and Nights as have been demonstrated by Copernicus For if the Circle abcd in the 3d Figure be the Ecliptick whose Center is e and Diameter aec and the Earth be placed in a the Sunne be moved in the little Circle fghi namely according to the order f g h i it hath been demonstrated that a Body placed in a will be moved in the same order through the points of the Ecliptick a b c d and will alwayes keep its Axis parallel to its self But if as I have supposed the Earth also be moved with Simple Circular Motion in a plain that passeth through a cutting the plain of the Ecliptick so as that the common section of both the plains be in ac thus also the Axis of the Earth will be kept alwayes parallel to it self For let the Center of the Earth be moved about in the Circumference of the Epicycle whose Diameter is lak which is a part of the straight line lac Therefore lak the Diameter of the Epicycle passing through the Center of the Earth will be in the plain of the Ecliptick Wherefore seeing that by reason of the Earths Simple Motion both in the Ecliptick and in its Epicycle the straight line lak is kept alwayes parallel to it self every other straight line also taken in the Body of the Earth and consequently its Axis will in like manner be kept alwayes parallel
reach the Zodiack of the fixed Starres wil fall stil upon the same fixed Starres because the whole Orbe a b c d is supposed to have no magnitude at all in respect of the great distance of the fixed Starres Supposing now the Sun to be in c it remains that I shew the cause why the Earth is neerer to the Sunne when in its annual motion it is found to be in d then when it is in b. And I take the cause to be this When the Earth is in the beginning of Capricorn at b the Sunne appears in the beginning of Cancer at d then is the midst of Summer But in the midst of Summer the Northern parts of the Earth are towards the Sunne which is almost all dry land containing all Europe and much the greatest part of Asia and America But when the Earth is in the beginning of Cancer at d it is the midst of Winter and that part of the Earth is towards the Sunne which contains those great Seas called the South Sea and the Indian Sea which are of farre greater extent then all the dry Land in that Hemisphere Wherefore by the last Article of the 21 Chapter when the Earth is in d it will come neerer to its first Movent that is to the Sunne which is in t that is to say the Earth is neerer to the Sunne in the midst of Winter when it is in d then in the midst of Summer when it is b and therefore during the Winter the Sunne is in its Perigaeum and in its Apogaeum during the Summer And thus I have shewn a possible cause of the Excentricity of the Earth which was to be done I am therefore of Keplers opinion in this that he attributes the Excentricity of the Earth to the difference of the parts thereof and supposes one part to be affected and another disaffected to the Sunne And I dissent from him in this that he thinks it to be by Magnetick virtue and that this Magnetick virtue or attraction and thrusting back of the Earth is wrought by immateriate Species which cannot be because nothing can give motion but a Body moved and contiguous For if those Bodies be not moved which are contiguous to a Body unmoved how this Body should begin to be moved is not imaginable as has been demonstrated in the 7th Article of the 9th Chapter and often inculcated in other places to the end that Philosophers might at last abstain from the use of such unconceiveable connexions of words I dissent also from him in this that he says the similitude of Bodies is the cause of their mutual attraction For if it were so I see no reason why one Egg should not be attracted by another If therefore one part of the Earth be more affected by the Sunne then another part it proceeds from this that one part hath more water the other more dry land And from hence it is as I shewed above that the Earth comes neerer to the Sunne when it shines upon that part where there is more water then when it shines upon that where there is more dry Land 9 This Excentricity of the Earth is the cause why the way of its annual motion is not a perfect Circle but either an Elliptical or almost an Elliptical line as also why the Axis of the Earth is not kept exactly parallel to it self in all places but onely in the Equinoctial points Now seeing I have said that the Moon is carried about by the Earth in the same manner that the Earth is by the Sunne and that the Earth goeth about the Sunne in such manner as that it shews sometimes one Hemisphere sometimes the other to the Sunne it remains to be enquired why the Moon has alwayes one and the same face turned towards the Earth Suppose therefore the Sunne to be moved with Simple Motion in the little Circle f g h i in the fourth figure whose Center is t and let ♈ ♋ ♎ ♑ be the annuall Circle of the Earth and a the beginning of Libra About the point a let the little Circle l k be described and in it let the Center of the Earth be understood to be moved with Simple motion and both the Sunne the Earth to be moved according to the order of the Signes Upon the Center a let the way of the Moon m n o p be described and let q r be the Diameter of a Circle cutting the Globe of the Moon into two Hemispheres whereof one is seen by us when the Moon is at the full and the other is turned from us The Diameter therefore of the Moon q o r will be perpendicular to the Straight Line t a. Wherefore the Moon is carried by reason of the Motion of the Earth from o towards p. But by reason of the motion of the Sunne if it were in p it would at the same time be carried from p towards o and by these two contrary Movents the straight line q r will be turned about and in a Quadrant of the Circle m n o p it will be turned so much as makes the fourth part of its whole conversion Wherefore when the Moon is in p q r will be parallel to the straight line m o. Secondly when the Moon is in m the straight line q r will by reason of the motion of the Earth be in m o. But by the working of the Suns motion upon it in the quadrant p m to◠same q r will be turned so much as makes another quarter of its whole conversion When therefore the Moon is in m q r will be perpendicular to the straight line o m. By the same reason when the Moon is in n q r will be parallel to the straight line m o and the Moon returning to o the same q r will return to its first place and the Body of the Moon will in one entire period make also one entire conversion upon her own Axis In the making of which it is manifest that one and the same face of the Moon is always turned towards the Earth And if any Diameter were taken in that little Circle in which the Moon were supposed to be carried about with simple motion the same effect would follow for if there were no action from the Sun every Diameter of the Moon would be carried about always parallel to it self Wherefore I have given a possible cause why one and the same face of the Moon is alwayes turned towards the Earth But it is to be noted that when the Moon is without the Ecliptick we do not alwayes see the same face precisely For we see onely that part which is illuminated But when the Moon is without the Ecliptick that part which is towards us is not exactly the same with that which is illuminated 10 To these three simple motions one of the Sunne another of the Moon and the third of the Earth in their own little Circles f g h i l k q r together with the Diurnal
as it is in the triangle CGK which is neerest to the First Light the transverse beames make Greenesse and when the same Second Light is weaker as in the triangle CKL they make a Purple colour 14 From hence may be deduced a cause why the Moon and Starres appear bigger and redder neer the Horizon then in the Mid-heaven For between the Eie and the apparent Horizon there is more impure aire such as is mingled with Watery and Earthy little Bodies then is between the same Eie and the more elevated part of Heaven But Vision is made by Beames which constitute a Cone whose base if we look upon the Moon is the Moons Face and whose vertex is in the Eie and therefore many beams from the Moon must needs fall upon little Bodies that are without the Visual Cone and be by them reflected to the Eie But these reflected beams tend all in lines which are transverse to the Visual Cone and make at the Eie an angle which is greater then the angle of the Cone Wherefore the Moon appeares greater in the Horizon then when she is more elevated And because those reflected beames go transversely there will be generated by the last article Rednesse A possible cause therefore is shewne why the Moon as also the Starres appear Greater and Redder in the Horizon then in the midst of heaven The same also may be the cause why the Sunne appears in the Horizon Greater and of a colour more degenerating to Yellow then when he is higher elevated For the reflection from the little Bodies between and the transverse motion of the Medium are still the same But the Light of the Sunne is much stronger then that of the Moon and therefore by the last article his Splendor must needs by this perturbation degenerate into Yellownesse But for the generation of these four colours it is not necessary that the figure of the Glass be a Prisma for if it were Spherical it would doe the same For in a Sphere the Sunne-beames are twice refracted and twice reflected And this being observed by Des Cartes and with all that a Rainebow never appeares but when it rains as also that the drops of raine have their figures almost Spherical he hath shewne from thence the cause of the colours in the Rainbow which therefore need not be repeated 15 Whiteness is Light but Light perturbed by the reflexions of many beams of Light comming to the Eye together within a little space For if Glass or any other Diaphanous Body be reduced to very small parts by contusion or concussion every one of those parts if the Beams of a lucid Body be from any one point of the same reflected to the Eye will represent to the beholder an Idea or Image of the whole lucid Body that is to say a Phantasme of White For the strongest Light is the most White and therefore many such parts will make many such Images Wherefore if those parts lie thick and close together those many Images will appear confusedly and will by reason of the confused Light represent a White Colour So that from hence may be deduced a possible cause why Glass beaten that is reduced to powder looks White Also why Water and Snow are White they being nothing but a heap of very small Diaphanous Bodies namely of little Bubbles from whose several convex Superficies there are by reflexion made several confused Phantasmes of the whole lucid Body that is to say Whiteness For the same reason Salt and Nitre are White as consisting of small Bubbles which contain within them Water and Aire as is manifest in Nitre from this that being thrown into the fire it violently blowes the same which Salt also doth but with less violence But if a White Body be exposed not to the Light of the Day but to that of the Fire or of a Candle it will not at the first sight be easily judged whether it be White or Yellow the cause whereof may be this that the light of those things which burn and flame is almost of a middle Colour between Whiteness and Yellowness 16 As Whiteness is Light so Blackness is the privation of Light or Darkness And from hence it is First that all Holes from which no light can be reflected to the Eie appear Black Secondly that when a Body hath little eminent particles erected straight up from the Superficies so that the Beams of Light which fall upon them are reflected not to the Eie but to the Body it self that Superficies appears Black in the same manner as the Sea appears Black when ruffled by the Wind. Thirdly that any combustible matter is by the fire made to look Black before it shines For the endeavour of the fire being to dissipate the smallest parts of such Bodies as are thrown into it it must first raise and erect those parts before it can work their dissipation If therefore the fire be put out before the parts be totally dissipated the Cole will appear Black for the parts being onely erected the Beams of Light falling upon them will not be reflected to the Eie but to the Cole it self Fourthly that Burning Glasses do more easily burn Black things then White For in a White Superficies the eminent parts are convex like little bubbles and therefore the Beams of Light which fall upon them are reflected every way from the reflecting Body But in a Black Superficies where the eminent particles are more erected the Beams of Light falling upon them are all necessarily reflected towards the Body it self and therefore Bodies that are Black are more easily set on fire by the Sun-beams then those that are White Fifthly that all Colours that are made of the mixture of White and Black proceed from the different position of the particles that rise above the Superficies and their different forms of asperity For according to these differences more or fewer Beams of Light are reflected from several Bodies to the Eie But in regard those differences are innumerable and the Bodies themselves so small that we cannot perceive them the explication and precise determination of the Causes of all Colours is a thing of so great difficulty that I dare not undertake it CHAP. XXVIII Of Cold Wind Hard Ice Restitution of Bodies bent Diaphanous Lightning and Thunder and of the Heads of Rivers 1 Why Breath from the same mouth sometimes heats and sometimes cools 2 Wind and the Inconstancy of Winds whence 3 Why there is a constant though not a great Wind from East to West neer the Equator 4 What is the effect of Aire pent in between the Clouds 5 No change from Soft to Hard but by motion 6 What is the cause of Cold neer the Poles 7 The cause of Ice and why the Cold is more remiss in rainy then in clear weather Why water doth not freeze in deep Wells as it doth neer the Superficies of the Earth Why Ice is not so heavy as Water and why Wine is not so easily frozen
it follows necessarily from hence that by reason of the fermentation of the whole Aire of which I have spoken in the 21 Chap. some of those Atomes meeting with others will cleave together by applying themselvs to one another in such manner as is agreeable to their motions and mutual contacts and seeing there is no Vacuum cannot be pulled asunder but by so much force as is sufficient to overcome their Hardness Now there are innumerable degrees of Hardness As for example there is a degree of it in Water as is manifest from this that upon a plain it may be drawn any way at pleasure by ones finger There is a greater degree of it in clammy liquors which when they are poured out doe in falling downwards dispose themselves into one continued thred which thred before it be broken will by little and little diminish its thickness till at last it be so small as that it seems to break onely in a point and in their separation the external parts break first from one another and then the more internal parts successively one after another In Wax there is yet a greater degree of Hardness For when we would pull one part of it from another we first make the whole mass slenderer before we can pull it asunder And how much the harder anything is which we would break so much the more force we must apply to it Wherefore if we go on to harder things as Ropes Wood Metals Stones c. reason prompteth us to believe that the same though not alwayes sensibly will necessarily happen and that even the hardest things are broken asunder in the same manner namely by Solution of their continuity begun in the outermost Superficies and proceeding successively to the innermost parts In like manner when the parts of Bodies are to be separated not by pulling them asunder but by breaking them the first separation will necessarily be in the convex Superficies of the bowed part of the Body and afterwards in the concave Superficies For in all bowing there is in the convex Superficies an endeavour in the parts to go one from another and in the concave Superficies to penetrate one another This being well understood a reason may be given how two Bodies which are contiguous in one common Superficies may by force be separated without the introduction of Vacuum though Lucretius thought otherwise believing that such separation was a strong establishment of Vacuum For a Marble Pillar being made to hang by one of its bases if it be long enough it will by its own weight be broken asunder and yet it will not necessarily follow that there should be Vacuum seeing the solution of its continuity may begin in the Circumference and proceed successively to the midst thereof Lastly Wine is not so easily congeled as Water because in Wine there are particles which being not fluid are moved very swiftly and by their motion congelation is retarded but if the Cold prevail against this motion then the outermost parts of the Wine will be first frozen and afterwards the inner parts whereof this is a signe that the Wine which remains unfrozen in the midst will be very strong 9 Another cause of Hardness in some things may be in this manner If a soft Body consist of many hard particles which by the intermixture of many other fluid particles cohaere but loosely together those fluid parts as hath been shewn in the last Article of the 21 Chapter will be exhaled by which means each hard particle will apply it self to the next to it according to a greater Superficies and consequently they will cohaere more closely to one another that is to say the whole mass will be made Harder 10 Again in some things Hardness may be made to a certain degree in this manner When any fluid substance hath in it certain very small Bodies intermingled which being moved with simple motion of their own contribute like motion to the parts of the fluid substance and this be done in a small enclosed space as in the hollow of a little Sphere or a very slender Pipe if the motion be vehement and there be a great number of these small enclosed Bodies two things will happen the one that the fluid substance will have an endeavour of dilating it self at once every way the other that if those smal Bodies can no where get out then from their reflexion it will follow that the motion of the parts of the enclosed fluid substance which was vehement before will now be much more vehement Wherefore if any one particle of that fluid substance should be touched pressed by some external Movent it could not yeild but by the application of very sensible force Wherefore the fluid substance which is enclosed and so moved hath some degree of Hardness Now greater and less degree of Hardness depends upon the quantity and velocity of those small Bodies and upon the narrowness of the place both together 11 Such things as are made Hard by sudden heat namely such as are hardned by fire are commonly reduced to their former soft form by Maceration For fire hardens by Evaporation and therefore if the evaporated moisture be restored again the former nature and form is restored together with it And such things as are frozen with Cold if the Wind by which they were frozen change into the opposite quarter they will be unfrozen again unless they have gotten a habit of new motion or endeavour by long continuance in that hardness Nor is it enough to cause thawing that there be a cessation of the freezing Wind for the taking away of the Cause doth not destroy a produced effect but the thawing also must have its proper cause namely a contrary Wind or at least a Wind opposite in some degree And this we finde to be true by experience For if Ice be laid in a place so well enclosed that the motion of the Aire cannot get to it that Ice will remain unchanged though the place be not sensibly cold 12 Of Hard Bodies some may manifestly be bowed others not but are broken in the very first moment of their bending And of such Bodies as may manifestly be bended some being bent do as soon as ever they are set at liberty Restore themselves to their former posture others remain still bent Now if the cause of this Restitution be asked I say it may be in this manner namely that the particles of the bended Body whilest it is held bent do nevertheless retain their motion and by this motion they restore it as soon as the force is removed by which it was bent For when any thing is bent as a plate of steel and as soon as the force is removed restores it self again it is evident that the cause of its restitution cannot be referred to the ambient aire nor can it be referred to the removal of the force by which it was bent for in things that are at rest the taking away of impediments is
times of their descents cannot be easily measured with sufficient exactness and also because the places neer the Poles are inaccessible Nevertheless this we know that by how much the neerer we come to the Poles by so much the greater are the Flakes of the Snow that falls and by how much the more swiftly such Bodies descend as are fluid and dissipable by so much the smaller are the particles into which they are dissipated 5 Supposing therefore this to be the cause of the Descent of Heavy Bodies it will follow that their motion will be accelerated in such manner as that the spaces which are transmitted by them in the several times will have to one another the same proportion which the odd numbers have in succession from Unity For if the straight line EA be divided into any number of equal parts the Heavy Body descending will by reason of the perpetual action of the Diurnal motion receive from the aire in every one of those times in every several point of the streight line EA a several new and equal impulsion and therefore also in every one of those times it will acquire a several and equal degree of celerity And from hence it follows by that which Galilaeus hath in his Dialogues of Motion demonstrated that Heavy Bodies descend in the several times with such differences of transmitted spaces as are equal to the differences of the square numbers that succeed one another from Unity which square numbers being 1 4 9 16 c. their differences are 3 5 7 that is to say the odd numbers which succeed another from Unity Against this cause of Gravity which I have given it will perhaps be objected that if a Heavy Body be placed in the bottom of some hollow Cylinder of Iron or Adamant and the bottom be turned upwards the Body will descend though the aire above cannot depress it much less accelerate its motion But it is to be considered that there can be no Cylinder or Cavern but such as is supported by the Earth and being so supported is together with the Earth carried about by its diurnal Motion For by this means the bottom of the Cylinder will be as the Superficies of the Earth and by thrusting off the next and lowest aire will make the uppermost aire depress the Heavy Body which is at the top of the Cylinder in such manner as is above explicated 6 The Gravity of Water being so great as by experience wee find it is the reason is demanded by many why those that Dive how deep soever they go under water do not at all feel the weight of the water which lyes upon them And the cause seems to be this that all Bodies by how much the Heavier they are by so much the greater is the endeavour by which they tend downwards But the Body of a Man is Heavier then so much water as is equal to it in magnitude and therefore the endeavour downwards of a Mans Body is greater then that of water And seeing all endeavour is motion the Body also of a Man will be carried towards the bottom with greater Velocity then so much water Wherefore there is greater Reaction from the bottom and the Endeavour upwards is equal to the endeavour downwards whether the water be pressed by water or by another Body which is Heavier then water And therefore by these two opposite equal endeavours the endeavour both ways in the water is taken away and consequently those that Dive are not at all pressed by it Coroll From hence also it is manifest that water in water hath no Waight at all because all the parts of water both the parts above and the parts that are directly under tend towards the bottom with equal endeavour and in the same straight lines 7 If a Body float upon the water the waight of that Body is equal to the waight of so much water as would fill the place which the immersed part of the Body takes up within the water Let EF in the 3d figure be a Body floating in the water ABCD and let the part E be above and the other part F under the water I say the waight of the whole Body EF is equal to the waight of so much water as the Space F will receive For seeing the waight of the Body EF forceth the water out of the space F and placeth it upon the Superficies AB where it presseth downwards it follows that from the resistance of the bottom there will also be an endeavour upwards And seeing again that by this endeavour of the water upwards the Body EF is lifted up it follows that if the endeavour of the Body downwards be not equal to the endeavour of the water upwards either the whole Body EF will by reason of that inequality of their endeavours or moments be raised out of the water or else it will descend to the bottom But it is supposed to stand so as neither to ascend nor descend Wherefore there is an Aequilibrium between the two endeavours that is to say the waight of the Body EF is equal to the waight of so much water as the Space F will receive Which was to be proved 8 From hence it follows that any Body of how great magnitude soever provided it consist of matter less Heavy then water may nevertheless float upon any quantity of water how little soever Let ABCD in the 4th figure be a vessel and in it let EFGH be a Body consisting of matter which is less Heavy then water and let the space AGCF be filled with water I say the Body EFGH will not sink to the bottom DC For seeing the matter of the Body EFGH is less Heavy then Water if the whole space without ABCD were full of Water yet some part of the Body EFGH as EFIK would be above the Water and the waight of so much water as would fill the space IGHK would be equal to the waight of the whole Body EFGH and consequently GH would not touch the bottom DC As for the sides of the vessel it is no matter whether they be hard or fluid for they serve onely to terminate the Water which may be done as well by water as by any other matter how hard soever and the water without the Vessel is terminated somewhere so as that it can spread no further The part therefore EFIG will be extant above the water AGCF which is contained in the vessel Wherefore the Body EFGH will also float upon the water AGCF how little soever that water be which was to be demonstrated 9 In the 4th Article of the 26th Chapter there is brought for the proving of Vacuum the experiment of water enclosed in a vessel which water the Orifice above being opened is ejected upwards by the impulsion of the aire It is therefore demanded seeing water is Heavier then aire how that can be done Let the 2d figure of the same 26th Chap. be considered where the water is with great force injected by
to be setled any where as at H. If now the heat of the aire be augmented the water will descend below H and if the heat be diminished it will ascend above it Which though it be certainely known to be true by experience the cause neverthelesse hath not as yet been discovered In the 6 and 7 articles of the 27th chapter where I consider the cause of Cold I have shewne that fluid Bodies are made colder by the pressure of the aire that is to say by a constant Wind that presseth them For the same cause it is that the Superficies of the water is pressed at F and having no place to which it may retire from this pressure besides the cavity of the Cylinder between H and E it is therefore necessarily forced thither by the Cold and consequently it ascendeth more or lesse according as the Cold is more or lesse encreased And againe as the Heat is more intense or the Cold more remisse the same water will be depressed more or lesse by its own Gravity that is to say by the cause of Gravity above explicated 13 Also Living creatures though they be Heavy can by Leaping Swimming Flying raise themselvs to a certain degree of height But they cannot do this except they be supported by some resisting Body as the Earth the Water and the Aire For these motions have their beginning from the contraction by the helpe of the Muscles of the Body animate For to this contraction there succeedeth a distension of their whole Bodies by which distension the Earth the Water or the Aire which supporteth them is pressed and from hence by the reaction of those pressed Bodies Living Creatures acquire an endeavour upwards but such as by reason of the Gravity of their Bodies is presently lost againe By this endeavour therefore it is that Living creatures rayse themselues up a little way by Leaping but to no great purpose but by Swimming Flying they raise themselves to a greater height because before the effect of their endeavour is quite extinguished by the Gravity of their bodies they can renew the same endeavour againe That by the power of the Soule without any antecedent contraction of the Muscles or the helpe of something to support him any man can be able to raise his Body upwards is a childish conceipt For if it were true a man might raise himselfe to what height he pleased 14 The diaphanous Medium which surrounds the Eie on all fides is invisible Nor is Aire to be seen in Aire nor Water in Water nor any thing but that which is more opacous But in the confines of two diaphanous Bodies one of them may be distinguished from the other It is not therefore a thing so very ridiculous for ordinary people to think all that Space empty in which we say is Aire it being the worke of Reason to make us conceive that the Aire is any thing For by which of our Senses is it that we take notice of the Aire seeing we neither See nor Hear nor Tast nor Smell nor Feel it to be any thing When we feel Heat we do not impute it to the Air but to the Fire nor do we say the aire is Cold but we our selves are Cold and when we feel the Wind we rather think something is comming then that any thing is already come Also we do not at al feel the waight of water in water much less of air in air That we come to know that to be a Body which we call Aire it is by Reasoning but it is from one Reason onely namely because it is impossible for remote Bodies to work upon our Organs of Sense but by the help of Bodies intermediate without which we could have no sense of them till they came to be contiguous Wherefore from the Senses alone without reasoning from effects we cannot have sufficient evidence of the nature of Bodies For there is under-ground in some Mines of Coles a certain matter of a middle nature between Water and Aire which nevertheless cannot by Sense be distinguished from aire for it is as Diaphanous as the purest aire and as farre as Sense can judge equally penetrable But if we look upon the effect it is like that of water For when that matter breaks out of the Earth into one of those Pits it fils the same either totally or to some degree and if a Man or Fire be then let down into it it extinguishes them in almost as little time as water would do But for the better understanding of this Phaenomenon I shall describe the 6th figure In which let A B represent the pit of the Mine and let part thereof namely C B be supposed to be filled with that matter If now a lighted Cādle be let down into it below C it wil as suddenly be extinguished as if it were thrust into water Also if a grate filled with coles throughly kindled and burning never so brightly be let down as soon as ever it is below C the fire will begin to grow pale and shortly after losing its light be extinguished no otherwise then if it were quenched in water But if the grate be drawn up again presently whilest the coles are still very hot the fire will by little and little be kindled again and shine as before There is indeed between this matter water this considerable difference that it neither wetteth nor sticketh to such things as are put down into it as water doth which by the moisture it leaveth hindereth the kindling again of the matter once extinguished In like manner if a Man be let down below C he will presently fall into a great difficulty of breathing and immediately after into a swoun and die unless he be suddenly drawn up again They therefore that go down into these pits have this custome that as soon as ever they feel themselves sick they shake the rope by which they were let down to signifie they are not well and to the end that they may speedily be pulled up again For if a man be drawn out too late void of sense and motion they digg up a Turff and put his face and mouth into the fresh earth by which means unless he be quite dead he comes to himself again by little and little and recovers life by the breathing out as it were of that suffocating matter which he had sucked in whilest he was in the pit almost in the same manner as they that are drowned come to themselves again by vomiting up the water But this doth not happen in all Mines but in some onely and in those not alwayes but often In such Pits as are subject to it they use this remedy They dig another pit as DE close by it of equal depth and joyning them both together with one common channel EF they make a Fire in the bottom E which carries out at D the aire contained in the pit DE and this draws with it the aire contained in the channel EF which
Iron by its action upon the Loadstone doth imprint in it an endeavour towards the other Pole namely towards the South Pole It happens therefore in these reciprocations or motions forwards and backwards of the particles of the Stone and of the Iron betwixt the North the South that whilest in one of them the motion is from North to South and the return from South to North in the other the motion wil be from South to North the return frō North to South which motions being opposite to one another and communicated to the Air the North Pole of the Iron whilest the attraction is working will be depressed towards the South Pole of the Loadstone or contrarily the North Pole of the Loadstone will be depressed towards the South Pole of the Iron and the Axes both of the Loadstone and of the Iron will be situate in the same straight line The truth whereof is taught us by experience As for the propagation of this Magnetical vertue not onely through the Aire but through any other Bodies how hard so ever it is not to be wondred at seeing no motion can be so weak but that it may be propagated infinitely through a space filled with Body of any hardness whatsoever For in a full Medium there can be no motion which doth not make the next part yeild and that the next and so successively without end so that there is no effect whatsoever but to the production thereof something is necessarily contributed by the several motions of all the several things that are in the World And thus much concerning the nature of Body in general with which I conclude this my first Section of the Elements of Philosophy In the first second and third Parts where the Principles of Ratiocination consist in our own Understanding that is to say in the legitimate use of such Words as we our selves constitute all the Theoremes if I be not deceived are rightly demonstrated The fourth Part depends upon Hypotheses which unless we know them to be true it is impossible for us to demonstrate that those Causes which I have there explicated are the true Causes of the things whose productions I have derived from them Nevertheless seeing I have assumed no Hypothesis which is not both possible and easie to be comprehended and seeing also that I have reasoned aright from those Assumptions I have withall sufficiently demonstrated that they may be the true Causes w ch is the end of Physical Contemplation If any other man from other Hypotheses shall demonstrate the same or greater things there wil be greater praise and thanks due to him then I demand for my self provided his Hypotheses be such as are conceivable For as for those that say any thing may be moved or produced by it Self by Species by its own Power by Substantial Forms by Incorporeal Substances by Instinct by Anteperistasis by Antipathy Sympathy Occult Quality and other empty words of Schoolmen their saying so is to no purpose And now I proceed to the Phaenomena of Mans Body Where I shall speak of the Opticks and of the Dispositions Affections and Manners of Men if it shall please God to give me life and shew their Causes AD CAP. XIV fig. 1. fig. 2. fig. 3. fig. 4. fig. 5. fig 6. fig 7. fig 8. fig 9. fig 10. AD CAP. XVI fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 fig 7 fig 8 fig 9 fig 10 fig 11 AD CAP. XVII fig. 1. fig. 2. fig. 3. fig. 4. fig. 5. fig. 6. fig. 7. fig. 8. Cap XVIII fig. 1. fig. 2. AD CAP. XIX fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 fig 7 fig 8 fig 9 fig 10 Cap XX. Fig 1 fig 2 fig 3 fig 4 fig 5 AD CAP XXI Fig 1 fig 2 fig 3 fig 4 fig 5 AD CAP XXII fig 1 fig 2 fig 3 AD CAP XXIII fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 fig 7 fig 8 fig 9 AD CAP. XXIIII fig 1 fig 2 fig 3 fig 4 fig 5 fig 6 AD Cap XXVI fig 1 Fig 2 fig 3 fig 4. fig 5. AD Cap XXVII fig 1. fig 2 AD Cap XXVIII et XXX fig 1. fig 2. fig 3 fig 4 fig 5. fig 6.