refraction 6. An answer to the arguments brought in favour of Monsieur des Cartes his opinion 7. The true cause of refraction of light both at its entrance and at its going out from the refleing body 8. A general rule to know the nature of reflection and refractions in all sorts of surface 9. A body of greater parts and greater pores makes a greater refraction than one of lesser parts and lesser pores 10. A confirmation of the former doctrine out of the nature of bodies that refract light CHAP. XIV Of the composition qualities Generation of mixed Bodies 1. The connexion of this chapter with the rest and the Authours intent in it 2. That there is a least sise of bodies and that this least sise is found in fire 3. The first conjunction of parts is in bodies of least sise and it is made by the force of Quantity 4. The second sort of conjunction is compactedness in simple Elements and it proceeds from density 5. The third conjunction is of parts of different Elements and it proceeds from quantity and density together 6. The reason why liquid bodies do easily joyn together and dry ones difficultly 7. That no two hard bodies can touch one another immediately 8. How mixed bodies are framed in general 9. The cause of the several degrees of solidity in mixed bodies 10. The Rule whereto are reduced all the several combinations of Elements in compounding of mixed bodies 11. Earth and water are the basis of all permanent mixed bodies 12. What kind of bodies those are where water is the basis and earth the predominant Element over the other two 13. Of those bodies where water being the basis air is the predominant Element 14. What kind of bodies result where water is the basis and fire the predominant Element 15. Of those bodies where water is in excess it alone being both the basis and the predominant Element 16. Of those bodies where earth alone is the basis and also the predominant in excess over the other three Elements 17. Of those bodies where earth is the basis water is the predominant element over the other two 18. Of those bodies where earth being the basis air is the predominant 19. Of those bodies where earth being the basis fire is the predominant 20. All the second qualities of mixed bodies arise from several combinations of the first qualities and are at last resolv'd into several degrees of rarity density 21. That in the Planets Stars there is a like variety of mixed bodies caused by light as here on earth 22. In what manner the Elements work on one another in the composition of mixed bodies and in particular fire which is the most active 23. A particular declaration touching the generation of Metals CHAP. XV. Of the Dissolution of Mixed Bodies 1. Why some bodies are brittle and others tough or apt to withstand outward violence the first instrument to dissolve mixed bodies 2. How outward violence doth work on the most compacted bodies 3. The several effects of fire the second and chiefest instrument to dissolve all compounded bodies 4. The reason why some bodies are not dissolved by fire 5. The reason why fire melteth gold but cannot consume it 6. Why Lead is easily consumed and calcinted by fire 7. Why and how some bodies are divided by fire into Spirits Waters Oyls Salts and Earth And what those parts are 8. How water the third instrument to dissolve bodies dissolvs calx into salt and so into terra damnata 9. How water mingled with salt becomes a most powerful Agent to dissolve other bodies 10. How putrefaction is caused CHAP. XVI An Explication of certain Maxims touching the operations and qualies of bodies and whether the Elements be found pure in any part of the world 1. What is the Sphere of activity in corporeal agents 2. The reason why no body can work in distance 3. An objection answer'd against the manner of explicating the former axiome 4. Of re-action and first in pure local motion that each Agent must suffer in acting and act in suffering 5. The former Doctrine applyed to other local motions design'd by particular names And that Suisseths argument is of no force against this way of doctrine 6. Why some notions do admit of intension and remission and others not 7. That in every part of our habitable world all the four elements are found pure in small atoms but not in any great bulk CHAP. XVII Of Rarefaction and Condensation the two first motions of Particular bodies 1. The Authours intent in this and the following chapters 2. That bodies may be rarified both by outward and inward heart and how this is perform'd 3. Of the great effects of Rarefaction 4. The first manner of condensation by heat 5. The second manner of condensation by cold 6. That Ice is not water rarified but condensed 7. How Wind Snow and Hail are made and wind by rain allaid 8. How parts of the same or divers bodies are joyn'd more strongly together by condensation 9. Vacuities cannot be the reason why water impregnated to the full with one kind of salt will notwithstanding receive more of another 10. The true reason of the former effect 11. The reason why bodies of the same nature do joyn more easily together than others CHAP. XVIII Of another motion belonging to Particular bodies called Attraction and of certain operations term'd Magical 1. What Attraction is and from whence it proceeds 2. The true sense of the Maxime that Nature abhors from vacuitys 3. The true reason of attraction 4. Water may be brought by the force of attraction to what height soever 5. The doctrine touching the attraction of water in Syphons 6. That the Syphon doth not prove water to weigh in its own orb 7. Concerning attraction caus'd by fire 8. Concerning attraction made by virture of hot bodies amulets c 9. The natural reason given for divers operations esteem'd by some to be magical CHAP. XIX Of three other motions belonging to particular bodies Filtration Restitution and Electrical attraction 1. What is Filtration and how it is effected 2. What causes the water in Filtration to ascend 3. Why the filter will not drop unless the label hang lower than the water 4. Of the motion of Restitution and why some bodies stand bent others not 5. Why some bodies return only in part to their natural figure others entirely 6. Concerning the nature of those bodies which shrink aand stretch 7. How great and wonderful effects proceed from small plain and simple principles 8. Concerning Electrical attratâ—on and the causes of it 9. Cabeus his opinion refuted concerning the cause of Electrical motions CHAP. XX. Of the Loadstones generation and its particulas motions 1. The extreme heat of the Sun under the Zodiack draws a stream of air from each Pole into the torrid Zone 2. The atomes of these two streams coming together are apt to incorporate with one another 3. By the meeting and mingling together
Of the great effects of Rarefaction 4. The first manner of condensation by heat 5. The second manner of condensation by cold 3. That Ice is not water rarifiâ—d but condensed 7. How wind snow and hail are made and wind by rain allayed 8. How parts of the same or divers bodies are joyned more strongly together by condensation 9. Vacuities cannot be the reason why water impregnated to the full with one kind of salt will notwithstanding receive more of another 10. The true reason of the former effect 11. The reason why bodies of the same nature jâ—yn more easily together then others 1. What attraction is and from whence it proceeds 1. The true sense of the Maxime that Nature abhors from vacuity 3. The true rea son of attraction 4. Water may be brought by the force of attraction to what height soever 5. The doctrine touching the attraction of water in Syphons 6. That the Syphon doth not prove water to weigh in its own orb 7. Concerning attraction caused by fire 8. Concerning attraction made by virtue of hot bodies amulets c. 9. The natural reason given for divers operations esteemed by some to be magical 1. What is Filtration and how it is effected 2. What causes the water in filtration to ascend 3. Why the filter will not drop unless the label hang lower then the water 4. Of the motion of Râ—stitution and why some bodies stand bent others not 5. Why some bo dies return only in part to their natural figure others entirely 6. Concerning the nature of those bodies which shrink and stretch 7. How great wonderful effects proceed from smal plain and simple principles 8. Concerning Electrical at action and the causes of it 6. Cabeus his opinion reâ—uted concerning the cause of Electrical motions 1. The extreme heat of the Sun under the Zodiack draws a stream of air from each pole into the Torrid Zone * Chap. 18. Sect. 7. 2. The Atoms of these two streams coming together are apt to incorporate with one another 3. By the meeting and mingling together of these streams at the Equator divers rivolets of Atoms of each Pole are continuated from one Pole to the other 4. Of these Atoms incorporated with some fit matter in the bowels of the earth is made a stone 5. This stone works by emanations joyned with agreeing streams that meet them in the air and in fine it is a Loadstone 6 A methode for making experiences on any subject 7. The Loadstones generation by atoms flowing from both Poles is confirmd by experiments observ'd in the stone it self 8. Experiments to prove that the Loadstone works by emanations meeting with agreeing streames 1. The operations of the loadstone are wrought by bodies and not by qualities 2. Objections against the former position answer'd 3. The Loadstone is imbued with his virtue from another body 4 The virtue of the Loadstone is a double and not one simple virtue 5. The virtue of the Loadstone works more strongly in the poles of it then in any other part 6. The loadstone sends forth its emanations spherically Which are of two kindâ— and each kind is strongest in that Hemisphere through whose polary parts they issue out 7. Putting two loadstones within the sphere of one another every part of one loadstone doth not agree wâ—th every part of the other loadstone 8. Concetning the declination and other respects of a needle towards the loadstone it touches 8. The virtue of the Loadstone goes from end to end in lines almost parallel to the Axis 10. The virtue of the Loadstone is not perfectly spherical though the stone be such 11. The intention of nature in all the operations of the loadstone is to make an union betwixt the attractive and attracted bodies 12. The main globe of the earth is not a Loadstone 13. The loadstone is generated in all parts or Climâ—t's of the earth 14. The conformity betwixt the two motions of magnetick things and of heavy things 1. Which is the North and which the South Pole of a Loadstone 2. Whether any bodies besides magnetick ones be attractive 3. Whether an iron placed perpendicularly towards the earth gets a magnetical virtue of pointing towards the north or towards the south in that end that lies downwards 4. Why loadstones affect iron better than one another 5. Gilberts reason refuted touching a cap'd Loadstone that takes up more iron then one not cap'd and an iron impregnated that in some case draws more strongly then the stone it self Galileus his opinion touching the former effects refuted 7. The Authors solution to the former questions 8. The reason why in the former case a lesser Loadstones draws the interjacent iron from the greater 9. Why the variation of a touched needle from the North is greater the nearer you go to the Pole 10. Whether in the same part of the world a touched needle may it one time vary more fâ—om the North and at another time less 11. The whâ—le doctrine of the loâ—dstone sum'd up in short 1. The connexion of the following Chapters with the precedent ones 2. Concerning several compositions of mixed bodies 3. Two sorts of Living Creatures 4. An engine to express the first sort of living creatures 5. Another Engine by which may be expressed the second sort of living creatures 4. The two former engines and some other comparisons applied to express the two several sorts of living creatures 7. How plants are framed 8. How Sensitive Creatures are formed 1. The opinion that the seed contains formally every part of the parent 2. The former opinion rejected 3. The Authours opinion of this question 4. Their opinion refuted who hold that every thing contains formally all things 5. The Authors opinion concerning the generation of Animals declared and confirm'd That one substance is changed into another 7. Concerning the hatching of Chickens and the generation of the other Animals 8. From whence it happens that the deficiences or excresences of the parents body are often seen in their children 9. The difference between the Authors opinion anâ—â—he former 〈◊〉 10 That the heart is imbued with the general specifike vertues of the whole body wherby is confirm'd the doctrine of the two former Paragraphes 11 That the heart is the first part generated in a living creatures 1. That the figure of an Animal is produced by ordinary second causes as well as any other corporeal effect 2. That the several figures of bodies proceed from a defect in one of three dimensions caused by the circumference of accidental causes 3. The former doctrine is confirmd by several instances 4. The same doctrine applyed to plants 4. The same doctrine declared in leaves of trees 16. The same applied to the bodies of Animals 7. In what sense the Author admits of vis formatrix 1. From whence proceeds the primary motion growth in Plants 2. Mr. des Cartes his opinion touching the motion of the heart 3. The former opinion rejected 4. The Authors opinion
activity and the great activity shews a great percussion burning being effected by a kind of attrition of the thing burned And the great force which fire shews in Guns and in Mines being but a multiplication of the same evidently convinces that of its own nature it makes a stong percussion when all due circumstances concur Whereas it has but little effect if the due circumstances be wanting as we may observe in the insensible burning of so rarified a body as pure spirit of wine converted into flame But we must examine the matter more parrticularly and seek the cause why a violent effect doth not always appear wherever light strikes For which we are to note that three things concur to make a percussion great The bigness the density and the celerity of the body moved Of which three there is onely one in light to wit celerity for it has the greatest rarity and the rays of it are the smallest parcels of all natural bodies and therfore since only celerity is considerable in the account of lights percussions we must examine what celerity is necessary to make the stroke of a ray sensible First then we see that all the motes of the aire nay even feathers and straws do make no sensible percussion when they fall upon us therefore we must in light have at the least a celerity that may be to the celerity of the straw falling upon our hand for example as the density of the straw is to the density of light that the percussion of light may be in the least degree sensible But let us take a corn of gunpowder instead of a straw between which there cannot be much difference and then putting that the density of fire is to the density of Gunpowder as 1. to 125000. and that the density of the light we have here in the earth is to the density of that part of fire which is in the Suns body as the body of the Sun is to that body which is called Orbis magnus whose Semidiameter is the distance between the Sun and the Earth which must be in subtriple proportion of the Diameter of the Sun to the Diameter of the great Orb it follows that 125000. being multiplyed by the proportion of the great Orb to the Sun which Galileo tells us is as 106000000. to one will give a scantling of what degree of celerity light must have more then a corn of Gunpowder to recompence the excess of weight which is in a corn of Gunpowder above that which is in a ray of light as big as a corn of Gunpowder Which will amount to be much greater than the proportion of the Semediameter of Orbis magnuâ— to the Semidiameter of the corn of Gunpowder for if you reckon five grains of Gunpowder to a Barly-corns breadth and 12. of them in an inch and 12. inches in a foot and 3. feet in a pace and 1000. paces in a mile and 3500. miles in the Semidiameter of the earth and 1208. Semidiamiters of the earth in the Semidiameter of the Orbis magnus there will be in it but 913 2480000000. grains of Gunpowder whereas the other calculation makes light to be 13250000000000 times rarer then gunpowder which is almost ten times a greater proportion then the other And yet this celerity supplies but one of the two conditions wanting in light to make its percussions sensible namely density Now because the same velocity in a body of a lesser bulk doth not make so great a percussion as it doth in a bigger body and that the littleness of the least parts of bodies follows the proportion of their rarity this vast proportion of celerity must again be drawn into it self to supply for the excess in bigness that a corn of gunpowder hath over an atome of light and the product of this multiplication will be the celerity required to supply for both defects Which evidently shews it is impossible that a ray of light should make any sensible percussion though it be a body Especially considering that sense never takes notice of what is perpetually done in a moderate degree And therefore after this minute looking into all circumstances we need not have difficulty in allowing to light the greatest celerity imaginable and a percussion proportionate to such a celerity in so rare a body and yet not fear any violent effect from its blow unless it be condens'd and many parts of it be brought together to work as if they were but one As concerning the last objection that if light were a body It would be fanned by the wind we must consider what is the cause of a thing appearing to be moved and then examine what force that cause hath in light As for the first part we see that when a body is discern'd now in one place now in another then it appears to be moved And this we see happens also in light as when the Sun or a candle is carried or moves the light thereof in the body of the Candle or Sun seems to be moved along with it And the like is in a shining cloud or comet But to apply this to our purpose We must note that the intention of the objection is that the light which goes from the fire to an opacous body far distant without interruption of its continuity should seem to be jog'd or put out of its way by the wind that crosses it Wherein the first failing is that the Objector conceives light to send species to our eye from the midst of its line whereas with a little consideration he may perceive that no light is seen by us but that which is reflected from an opacous body to our eye so that the light he means in his objection is never seen at all Secondly 't is manifest that the light which strikes our eye strikes it in a straight line and seems to be at the end of that straight line wherever that is and so can never appear to be in another place but the light which we see in another place we conceive to be another light Which makes it again evident that the light can never appear to shake though we should suppose that light may be seen from the middle of its line for no part of wind or air can come into any sensible place in that middle of the line with such speed that new light from the sourcce doth not illuminate it sooner then it can be seen by us wherefore it will appear to us illuminated as being in that place and therefore the light can never appear shaken And lastly it is easier for the air or wind to destroy the light then to remove it out of its place wherefore it can never so remove it out of its place as that we should see it in another place But if it should remove it it would wrap it up within it self and hide it In conclusion after this long dispute concerning the nature of light If we consider well what hath been said on both sides
could strike it But it is evident say you out of these pretended causes of this motion that such atomes cannot move so swiftly downwards as a great dense body since their littleness and their rarity are both of them hindering to their motion Therefore this cannot be cause of that effect which we call gravity To this I reply That to have the atoms give these blows to a descending dense body 't is not requir'd that their natural and ordinary motion should be swifter then the descent of such a dense body but the very descent of it occasions their striking it for as it falls and makes it self a way through them they divide themselves before it and swell on the sides and a little above it and presently close again behind it and over it assoon as it is past Now that closing to hinder vacuity of space is a sudden one and thereby attains great velocity which would carry the atoms in that degree of velocity further than the descending body if they did not encounter with it in their way to retard them which encounter and tarding implyes such strokes upon the dense body as we suppose to cause this motion And the like we see in water into which letting a stone fall presently the water that was divided by the stone and swells on the sides higher then it was before closes upon the back of the descending stone and follows it so violently that for a while after it leaves a purling hole in the place where the stone went down till by the repose of the stone the water returns likewise to its quiet and so its superficies becomes even In the third place an enquiry occurs emergent out of this doctrine of the cause of bodies moving upwards and downwards Which is Whether there would be any natural motion deep in the earth beyond the activity of the Sun beams for out of these principles it follows that there would not and consequently there must be a vast Orb in which there would be no motion of gravity or levity For suppose the Sun beams might pierce a thousand miles deep into the body of the earth yet there would still remain a mass whose Diameter would be near 5000 miles in which there would be no gravitation nor the contrary motion For my part I shall make no difficulty to grant the inference as far as concerns motion caused by our Sun for what inconvenience would follow out of it But I will not offer at determining whether there may not be enclosed within that great sphere of earth some other fire such as the Chymists talk of an Archeus a Demogorgon seated in the centre like the heart in animals which may raise up vapours and boyl an air out of them and divide gross bodies into atoms and accordingly give them motions answerable to ours but in different lines from ours according as that fire or Sun is situated Since the far-searching Authour of the Dialogues de Mundo hath left that speculation undecided after he had touched upon it in the Twelfth knot of his first Dialogue Fourthly it may be objected that if such descending atoms as we have described were the cause of a bodies gravity and descending towards the center the same body would at divers times descend more and less swiftly for example after midnight when the atoms begin to descend more slowly the same body would descend more slowly in a like proportion and not weigh so much as it did in the heat of the day The same may be said of Summer and Winter for in Winter time the atoms seem to be more gross and consequently to strike more strongly upon the bodies they meet with in their way as they descend yet on the other side they seem in the Summer to be more numerous as also to descend from a greater height both which circumstances will be cause of a stronger stroke and more vigorous impulse on the body they hit And the like may be objected of divers parts of the World for in the Torrid Zone it will always happen as in Summer in places of the Temperate Zone and in the Polar times as in deepest winter so that no where there should be any standard or certainty in the weight of bodies if it depended upon so mutable a cause And it makes to the same effect that a body which lies under a thick rock or any other very dense body that cannot be penetrated by any great store of atoms should not be so heavy as it would be in the open and free air where the atoms in their compleat numbers have their full strokes For answer to these and such like instances we are to note first that 't is not so much the number or violence of the percussion of the striking atoms as the density of the thing strucken which gives the measure to the descending of a weighty body and the chief thing which the stroak of the atoms gives to a dense body is a determination of the way which a dense body is to cut to it self therfore multiplication or lessening of the atoms will not make any sensible difference betwixt the weight of one dense body where manya toms strike and an other body of the same density where but a few strike so that the stroak downwards of the descending atoms be greater then the stroke upwards of the ascending atoms and therby determines it to weigh to the Centrewards and not rise floating upwards which is all the sensible effect we can perceive Next we may observe that the first particulars of the objection do not reach home to enfeeble our doctrine in this particular although we admit them to be in such sort as they are proposed for they withal imply such a perpetual variation of causes ever favourable to our position that nothing can be infer'd out of them to repugne against it As thus When there are many atoms descending in the air the same general cause which makes them be many makes them also be light in proportion to their multitude And so when they are few they are heavy likewise when the atoms are light the air is rarified and thin and when they are heavy the air is thick And so upon the whole matter 't is evident that we cannot make such a precise and exact judgement of the variety of circumstances as to be able to determine when there is absolutely more cause of weight and when less And as we find not weight enough in either side of these opposite circumstances to turn the scales in our discourse so likewise we find the same indifference in experience it self for the weights we use do weigh equally in mysty weather and in clear and yet in rigor of discourse we cannot doubt but that in truth they do not gravitate or weigh so much though the difference be imperceptible to sense when the air is thick and foggy as when its pure and rarified Which thickness of the Medium when it arrives to a very
to the iron though the other steam be never so great yet it cannot draw more then according to the proportion of its Antagonists coming from the iron Wherfore seeing the two steams betwixt the iron and the little Loadstone are more proportionable to one another and the steam coming out of the little loadstone is notably greater then the steam going from the iron to the greater Loadstone the conjunction must be made for the most part to the little loadstone And if this discourse doth not hold in the former part of the Probleme betwixt a second iron and Loadstone it is supplyed by the former reason which we gave for that particular purpose The third case depends also of this solution for the bigger an iron is so many more parts it hath to suck up the influence of the Loadstone and consequently doth it therby the more greedily and therfore the Loadstone must be carried to it more violently and when they aâ—e joyn'd stick more strongly The sixth question is Why the variations of the Needle from the true North in the Northern Hemisphere are greater the nearer you go to the Pole and lesser the nearer you approach to the Equator The reason wherof is plain in our doctrine For considering that the magnetick virtue of the earth streams from the North towards the Equator it follows of necessity that if there be two streams of magnetick flowrs issuing from the North one of them precisely from the pole the other from a part of the earth near the pole that the stream coming from the point by side the Pole be but a little the stronger of the two there will appear very little differences in their several operations after they have had a long space to mingle their emanations together which therby join and grow as it were into one stream wheras the nearer you come to the Pole the more you will find them severed and each of them working by its own virtue And very near the point which causes the variation each stream works singly by it self and therfore here the point of variation must be master and will carry the needle strongly to his course from the due North if his stream be never so little more efficacious then the other Again a line drawn from a point of the Earth wide of the Pole to a point of the Meridian near the Equator makes a less angle then a line drawn from the same point of the Earth to a point of the same Meridian nearer the Pole wherfore the variation being esteem'd by the quantities of the said angles it must needs be greater near the Pole then near the Equator though the cause be the same But because it may happen that in the parts near the Equator the variation may proceed from some piece of land not much more northerly then where the needle is but that it bears rather Easterly or Westerly from it and yet Gilbert's assertion goes universally when he says the variations in Southern regions are less then in Northern ones we must examine what may be the reason therof And presently the generation of the Loadstone shews it plainly For seeing the nature of the Loadstone proceeds out of this that the Sun works more upon the Torrid Zone then upon the poles and that his too strong operation is contrary to the Loadstone as being of the nature of fire it follows evidently that the lands of the Torrid Zone cannot be so magnetical generally speaking as the polar lands are and by consequence that a lesser land near the Pole will have a greater effect then a larger continent near the Equator and likewise a land further off towards the Pole will work more strongly then a nearer land which lyes towards the Equator The seventh question is Whether in the same part of the world a touched needle may at one time vary more from the true North point and at another time less In which Gilbert was resolute for the negative part but our latter Mathematicians are of another mind Three experiences were made neer London in three divers years The two first 42 years distant from one another and the third 12 years distant from the second And by them it is found that in the space of 54 years the Loadstone hath at London diminsh'd his variation from the North the quantity of 7 degrees and more But so that in the latter years the diminution hath sensibly gone faster then in the former These observations peradventure are but little credited by Strangers but we who know the worth of the men that made them cannot mistrust any notable errour in them for they were very able Mathematicians and made their observations with very great exactness and there were several judicious witnesses at the making of them as may be seen in Mr. Gillebrand's print concerning this subject And divers other particular persons confirm the same whose credit though each single might peradventure be slighted yet all in body make a great accession We must therfore cast about to find what may be the cause of an effect so paradox to the rest of the doctrine of the Loadstone for seeing that no one place can stand otherwise to the North of the earth at one time then at another how it is possible the needle should receive any new variation since all variation proceeds out of the inequality of the earth But when we consider that this effect proceeds not out of the main body of the earth but only out of the bark of it and that its bark may have divers tempers not as yet discover'd to us out of whose variety the influence of the earthy parts may be divers in respect of one certain place 't is not impossible but that such variation may be especially in England which Island lying open to the North by a great and vast Ocean may receive more particularly then other places the special influences and variation of the weather that happen in those Northeastern countreys from whence this influence comes to us If therfore there should be any cours of weather whose period were a hundred years for example or more or lesse and so might easily pass unmarked this variation might grow out of such a cours But in so obscure a thing we have already hazarded to guess too much And upon the whole matter of the Loadstone it serves our turn if we have proved as we conceive we have done fully that its motions which appear so admirable do not proceed from an occult quality but that the causes of them may be reduced to local motion and all perform'd by such corporeal instruments and means though peradventure more intricately disposed as all other effects are among bodies Whose ordering and disposing and particular progress there is no reason to despair of finding ouâ— would men but carefully apply themselvs to that work upon solid principles and with diligent experiences But because this matter has been very long and scatteringly
towards that side on which the shadow appears in respect of the opacous body or of the illuminant and so be a cause of deepness of Colour on that side if it happen to be fringed with colour CHAP. XXXI The causes of certain appearances in luminous Colours with a Conclusion of the discourse touching the Senses and the Sensible Qualities OUt of these grounds we are to seek the resolution of all such Symptoms as appear to us in this kind of colours First therfore calling to mind how we have already declared that the red colour is made by a greater proportion of light mingled with darkness and the blew with a less proportion it must follow that when light passes through a glass in such sort as to make colours the mixture of the light and darkness on that side where the light is strongest will encline to a red and their mixture on the otherside where the light is weakest will make a violet or blew And this we see fall out accordingly in the light which is tincted by going through a Prism for a red colour appears on that side from which the light dilates or encreases and a blew is on that side towards which it decreases Now if a dark body be placed within this light so as to have the light come on both sides of it we shall see the contrary happen about the borders of the picture or shadow of the dark body that is to say the red colour will be on that side of the picture which is towards or over against the blew colour made by the glass and the blew of the picture will be on that side which is towards the red made by the glass as you may experience if you place a slender opacous body along the Prism in the way of the light either before or behind the Prism The reason wherof is that the opacous body standing in the middle environ'd by light divides it and makes two lights of that which was but one each of which lights is comprised between two darknesses to wit between each border of Shadow that joyns to each extreme of the light that comes from the glass and each side of the Opacous bodies shadow Wherfore in each of these lights or rather in each of their comixtions with darkness there must be red on the one side and blew on the other according to the course of light which we have explicated And thus it falls out agreeable to the Rule we have given that blew comes to be on that side of the opacous bodies shadow on which the glass casts red and red on that side of it on which the glass casts blew Likewise when light going through a convex glass makes two cones the edges of the cone betwixt the glass the point of concourse will appear red if the room be dark enough and the edges of the further cone will appear blew both for the reason given For in this case the point of concourse is the strong light betwixt the two cones of which that betwixt the glass and the point is the stronger that beyond the point the weaker And for this very reason if an opacous body be put in the axis of these two cones both the sides of its picture will be red if it be held in the first cone which is next to the glass and both will be blew if the body be situated in the further cone for both sides being equally situated to the course of the light within its own cone there is nothing to vary the colours but only the strength and weakness of the two lights of the cones on this that side the point of the concourse which point being in this case the strong and clear light wherof we made general mention in our precedent note the cone towards the glass and the illuminant is the stronger side and the cone from the glass is the weaker In those cases where this reason is not concern'd we shall see the victory carried in the question of colours by the shady side of the opacous body that is the blew colour will still appear on that side of the opacous bodies shadow that is furthest from the illuminant But where both causes concur and contest for precedence there the course of the light carries it that is to say the red will be on that side of the opacous bodies shadow where it is thicker and darker and blew on the otherside where the shadow is not so strong although the shadow be cast that way that the red appears as is to be seen when a slender body is placed betwixt the Prism and the reflectant body upon which the light colours are cast through the Prism And 't is evident that this cause of the course of the shadow is in it self a weaker cause than the other of the course of light and must give way to it whenever they incounter as it cannot be expected but that in all circumstances shadows should be light because the colours which the glass casts in this case are much more faint and dusky than in the other For effects of this latter cause we see that when an opacous body lyes cross the Prism whiles it stands end-ways the red or blew colour will appear on the upper or lower side of its picture according as the illuminant is higher or lower then the transverse opacous body the blew ever keeping to that side of the picture that is furthest from the body and the illuminant that make it and the red the contrary Likewise if an opacous body be placed out of the axis in either of the cones we have explicated before the blew will appear on that side of the picture which is furthest advanced in the way that the shadow is cast and the red on the contrary And so if the opacous body be placed in the first cone beside the axis the red will appear on that side of the picture in the basis of the second cone which is next to the circumference and the blew on that side next the axis but if it be placed on one side of the axis in the second cone then the blew will appear on that side the picture is next the circumference and the red on that side which is next the center of the basis of the cone There remains yet one difficulty of moment to be determined which is Why when through a glass two colours namely blew and red are cast from a Candle upon a paper or wall if you put your eye in the place of one of the colours that shines upon the wall and so that colour comes to shine upon your eye so that another man who looks upon it will see thot colour plainly upon your eye nevertheless you shall see the other colour in the glass as for example if on your eye there shines a red you shall see a blew in the glass and if a blew shines upon your eye you shall see a
side an Incorporated Soul by reason of her being confined to the use her Senses can look on but one single definite place or time at once and needs a long chain of many discourses to comprehend all the circumstances of any one action and yet after all how short is she of comprehending all So that comparing one of these with the other 't is evident that the proportion of a Separated Soul to one in the Body is as all time or all place in respect of any one piece or least parcel of them or as the entire absolute comprehender of all time and all place is to the discoverer of a small measure of them For whatever a Soul wills in that state she wills it for the whole extent of her duration because she is then out of the state or capacitity of changing and wishes for whatever she wishes as for her absolute good and therfore employs the whole force of her judgment upon every particular wish Likewise the eminencie which a Separated Soul hath over place is also then entirely employ'd upon every particular wish of hers since in that state there is no variety of place left her to wish for such good in one place and to refuse it in another as while she is in the Body hapneth to every thing she desires Wherefore whatever she then wishes for she wishes for it according to her comparison to place that is to say that as such a Soul hath a power to work at the same time in all places by the absolute comprehension which she hath of place in abstract so every wish of that Soul if it were concerning a thing to be made in place were able to make it in all places through the excessive force and efficacy which she employs upon every particular wish The third effect by which among bodies we gather the vigour and energy of the cause that produces it to wiâ— the doing of the like action in a lesser time in a larger extent is but a combination of the two former 〈◊〉 therfore it requires no further particular insistance upon it to shew tha◠〈◊〉 〈◊〉 〈◊〉 this the proportion of a Separated to an 〈◊〉 Soul must needs be the self same as in the other seeing a Separated Soul's activity is upon all place is in an Indivisible of time Therfore to shut up this point there remains only for us to consider what addition may be made to the efficacity of a judgment by the concurrence of other extrinsecal helps We see that when an understanding man will settle any judgment or conclusion in his mind he weighs throughly all that follows out of such a judgment and considers likewise all the antecedents that lead him to iâ— and if after due reflection and examination of whatever concerns this conclusion which he is establishing in his mind he finds nothing to cross it but that every particular and circumstance goes smoothly along with and strengthens it he is then satisfied and quiet in his thoughts and yields a full assent therto which assent is the stronger the more concurrent testimonies he has for it And though he should have a perfect demonstration or sight of the thing in it self yet every one of the other extrinsecal proofs being as it were a new perswasion hath in it a further vigour to strengthen and content his mind in the fore-had demonstration for if every one of these be in it self sufficient to make the thing evident it cannot happen that any one of them should hinder the others but contrariwise every one of them must needs concurr with all the rest to the effectual quieting of his understanding in its assent to that judgment Now then according to this rate let us calculate if we can what concurrence of proofs and witnesses a Separated Soul will have to settle and strengthen her in every one of her judgments We know that all verities are chain'd and connected one to another and that there is no true conclusion so far remote from any other but may by more or less consequences and discourses be deduced evidently out of it it follows then that in the abstracted Soul where all such consequences are ready drawn and seen in themselvs without extention of time or employing of pains to collect them every particular verity bears testimony to any other so that every one of them is believ'd and works in the sence and virtue of all Out of which it is manifest that every judgment in such a Separated Soul hath an infinite strength and efficacity over any made by an embodyed one To sum all up in a few words We find three roots of infinity in every action of a Separated Soul compar'd to one in the Body First the freedom of her essence or substance it self Next that quality of hers by which she comprehends place and time that is all permanent and successive quantity and Lastly the concurrence of infinite knowledges to every action of hers Having then this measure in our hands let us apply it to a Well-order'd and to a Disorder'd Soul passing out of this world let us consider the oneset upon those goods which she shall there have present and shall fully enjoy the other languishing after and pining away for those which are impossible for her ever to obtain What joy what content what exultation of mind in any living man can be conceiv'd so great as to be compared with the happiness of one of these Souls And what grief what discontent what misery can be like the others These are the different effects which the divers manners of living in this world cause in Souls after they are deliver'd from their Bodies Out of which and the discourse that hath discover'd these effects to us we see a clear resolution of that so main and agitated question among the Philosophers Why a rational Soul is imprison'd in a gross Body of Flesh and Blood In truth the question is an illegitimate one as supposing a false ground for the Soul 's being in the Body is not an imprisonment of a thing that was existent before the Soul and Body met together but her being there is the natural course of begining that which can no other way come into the lists of nature For should a Soul by the course of nature obtain her first being without a Body either she would in the first instant of her being be perfect in knowledg or she would not if she were then would she be a perfect compleat immaterial substance not a Soul whose nature is to be a copartner to the Body and to acquire her perfection by the medâ—ation and service of corporeal senseâ— but if she were not perfect in Science but were only a capacity therto and like white paper in which nothing were yet written then unless she were 〈◊〉 into a Body she could never arrive to know any thing because motion alteration are effects peculiar to Bodies Therfore 〈◊〉 be agreed that she is naturally
quality it would always produce an equal to it self 5. The third reason because if we imagine to our selvs the substance of fire to be rarified it will have the same appearances which Light hath 6. The fourth reason from the manner of the generation and corruption of light which agrees with fire 7. The fifth reason because such properties belong to light as agree onely to bodies CHAP. VII Two Objections answer'd a gainst light being fire a more ample proof of its being such 1. That all light is hot and apt to heat 2. The reason why our bodies for the most part do not feel the heat of pure light 3. The experience of burning glasses and of soultry gloomy weather prove light to be fire 4. Philosophers ought not to judg of things by the rules of vulgar people 5. The different names of light and fire proceed from different Notions of the same Substance 6. The reason why many times fire and heat are deprived of light 7. What becometh of the body of light when it dies 8. An experiment of some who pretend that light may be precipitated into powder 9. The Authors opinion concerning Lamps pretended to have leen found in Tombs with inconsumptible lights CHAP. VIII An answer to three other Objections formerly proposed against Light being a Substance 1. Light is not really in every part of the room it enlightneth nor fills entirely any sensible part of it though it seem to us to do so 2. The least sensible point of a diaphanous body hath room sufficient to contain both air and light together with a multitude of beams issuing from several lights without penetrating one another 3. That light doth not enlighten any room in an instant and that the great celerity of its motion makes it imperceptible to our senses 4. The reason why the motion of light is not discern'd coming towards us and that there is some real tardity in it 5. The Planets are not certainly ever in that place where they appear to be 6. The reason why light being a body doth not by its motion shatter other bodies into pieces 7. The reason why the body of light is never perceiv'd to be fan'd by the wind 8. The Reasons for and against lights being a body compared together 9. A summary repetition of the reasons which prove that light is fire CHAP. IX Of Local Motion in common 1. No local motion can be perfored without succession 2. Time is the common measure of all succession 3. What velocity is and that it cannot be infinite 4. No force so little but is able to move the greatest weight imâ—nable 5. The chief principle of Mechannicks deduced out of the former discourse 6. No movable can pass from rest to any determinate degree of velocity or from a lesser degree to a greater without passing through all the intermediate degres which are below the obtained degree 7. The conditions which help to motion in the movable are three in the medium one 8. No body hath any intrinsecal virtue to move it self towards any determinate part of the Universe 9. The encrease of motion is always made in the proportion of the odd numbers 20. No motion can encrease for ever or without coming to a period 11. Certain Problems resolved concerning the proportion of some moving Agents compared to their effects 12. When a movable comes to rest the motion decreases according to the Rules of encrease CHAP. X. Of Gravity and Levity and of Local Motion commonly term'd Natural 1. Those motions are call'd natural which have constant causes and those violent which are contrary to them 2. The first and most general opeperation of the Sun is the making and raising of atomes 3. The light rebounding from the earth with atomes causes two streams in the air the one ascending the other descending and both of them in a perpendicular line 4. A dense body placed in the air between the ascending and descending stream must needs descend 5. A more particular explication of all the former doctrine touching gravity 6. Gravity and Levity do not signifie an intrinsecal inclination to such a motion in the bodies themselvs which are term'd heavy and light 7. The more dense a body is the more swiftly it descends 8. The velocity of bodies descending doth not encrease in proportion to the difference that may be between their several densities 9. More or lesse gravity produces a swifter or a slower descending of a heavy body Aristotles argument to disprove motion in vacuo is made good 10. The reason why at the inferior quarter of a circle a body descends faster by the Arch of that quarter than by the cord of it CHAP. XI An answer to objections against the causes of Natural Motion avow'd in the former Chapter and a refutation of the contrary opinion 1. The first objection answered why a hollow body descends slower than a solid one 2. The second objection answer'd and the reason shown why atomes do continually overtake the descending dense body 3. A curious question left undecided 4. The fourth objection answer'd why the descent of the same heavy bodies is equal in so great inequality of the atomes which cause it 5. The reason why the shelter of a thick body doth not hinder the descent of that which is under it 6. The reason why some bodies sink others swim 7. The fifth objection answer'd concerning the descending of heavy bodies in streams 8. The sixth objection answered and that all heavy elements doe weigh in their own spheres 9. The seventh objection answer'd and the reason why we do not feel the course of the air and atomes that beat continually upon us 10. How in the same body gravity may be greater than density and density than gravity though they be the same thing 11. The opinion of gravities being an intrinsecal inclination of a body to the centea refuted by reason 12. The same opinion refutedly several experiences CHAP. XII Of Violent Motion 1. The State of the question touching the cause of violent motion 2. That the medium is the only cause which continues violent motion 3. A further explication of the former doctrine 4. That the air hath strength enough to continue violent motion in a moveable 5. An answer to the first objection that air is not apt to conserve motion and how violent motion comes to cease 6. An answer to the second objection that the air hath no power over heavy bodies 7. An answer to the third objection that an arrow should fly faster broad wayes than long ways CHAP. XIII Of three sorts of Violent motion Reflection Undulation and Refraction 1. That reflection is a kind of violent motion 2. Reflection is made at equal angles 3. The causes and properties of undulation 4. Refraction at the entrance into the reflectent body is towards the perpendicular at the going out is from it when the second superficies is parallel to the first 5. A refutation of Monsieur des Cartes his explication of
of these streams at the Equator divers Rivolets of Atomes of each Pole are continuated from one Pole to the other 4. Of these Atomes incorporated with some fit matter in the bowels of the earth is made a stone 5. This stone works by emanatitions joyn'd with agreeing streams that meet them in the air and in fine it is a Loadstone 6. A Method for making experiences upon any subject 7. The Loadstones generation by Atomes flowing from both Poles is confirmed by experiments observed in the stone it self 8. Experiments to prove that the Loadstone works by emanations meeting with agreeing streams CHAP. XXI Positions drawn out of the former doctrine and confirm'd by experimental proofs 1. The operations of the Loadstone are wrought by bodies and not by qualities 2. Objections against the former position answer'd 3. The Loadstone is imbu'd with his vertue from another body 4. The vertue of the loadstone is a double and not one simple virtue 5. The vertue of the Loadstone works more strongly in the Poles of it than in any other part 6. The loadstone sends forth its emanations spherically Which are of two kinds and each kind is strongest in that hemisphere through whose polary parts they issue out 7. Putting two loadstones within the sphere of one another every part of one loadstone doth not agree with every part of the other loadstone 8. Concerning the declination and other respects of a needle towards the loadstone it touches 9. The vertue of the loadstone goes from end to end in lines almost parallel to the axis 10. The virtue of a loadstone is not perfectly spherical though the stone be such 11. The intention of nature in all the operations of the loadstone is to make an union betwixt the attractive and the attracted bodies 12. The main Globe of the earth not a loadstone 13. The loadstone is generated in all parts or climates of the earth 14. The conformity betwixt the two motions of magnetick things and of heavy things CHAP. XXII A solution of certain Problems concerning the Loadstone and a short summ of the whole doctrine touching it 1. Which is the North and which the South Pole of a loadstone 2. Whether any bodies besides magnetick ones be attractive 3. Whether an iron placed perpendicularly towards the earth doth get a magnetical virtue of pointing towards the North or towards the South in that end that lies downwards 4. Why loadstones affect iron better than one another 5. Gilbert's reason refuted touching a capped loadstone that takes up more iron than one not capped and an iron impregnated that in some case draws more strongly than the stone it self 6. Galileus his opinion touching the former effects refuted 7. The Authours solution to the former questions 8. The reason why in the former case a lesser Load stone draws the interjacent iron from the greater 9. Why the variation of a touched needle from the North is greater the nearer you go to the Pole 10. Whether in the same part of the world a touched needle may at one time vary more from the North and at another time lesse 11. The whole doctrine of the load stone summ'd up in short CHAP. XXIII A description of two sorts of Living creatures Plants and Animals and how they are framed in common to perform vital motion 1. The connexion of the following Chapters with the precedent 2. Concerning several compositions of mix'd bodies 3. Two sorts of living creatures 4. An engin to express the first sort of living creatures 5. An other engin by which may be express'd the second sort of living creatures 6. The two former enginâ— and some other compâ—risons upplyed express 〈◊〉 〈◊〉 〈◊〉 〈◊〉 of living creatures 7. How plants are fram'd 8. How Sensitive creatures are form'd CHAP. XXIV A more particular survey of the generation of Animals in which is discover'd what part of the animal is first generated 1. The opinion that the seed contains formally every part of the parent 2. The former opinion rejected 3. The Authours opinion of this question 4. Their opinion refuted who hold that every thing contains formally all things 5. The Authours opinion concerning the generation of Animals declared and confirm'd 6. That one substance is chang'd into another 7. Concerning the â—atching of Chickens and the generation of other animals 8. From whence it â—ppens that the defi◠〈◊〉 〈◊〉 â—scences of the 〈◊〉 〈◊〉 〈◊〉 seen in their children 9. The difference between the Authours opinion and the former 10. That the heart is iâ—ued with the generalâ— spâ—ific virtues of the whole body 〈◊〉 confirm'd the doctrine of the two former paragraphs 11. That the heart is the first part generated in a living creature CHAP. XXV How a Plant or Animal comes to that Figure it hath 1. That the Figure of an Animal is produced by ordinary second causes as well as any other corporeal effect 2. That the several figures of bodies proceed from a defect in one of the three dimensions caused by the concurrence of accidental causes 3. The former doctrine is confirmed by several instances 4. The same doctrine apply'd to Plants 5. The same doctrine declared in leafs of trees 6. The same apply'd to the bodies of Animals 7. In what sense the Authour admits of Vis formatrix CHAP. XXVI How motion begins in Living creatures And of the Motion of the Heart Circulation of the Blood Nutrition Augmentation and corruption or death 1. From whence proceeds the primary motion and growth in Plants 2. Monsieur des Cartes his opinion touching the motion of the heart 3. The former opinion rejected 4. The Authours opinion concerning the motion of the heart 5. The motion of the heart depends originally of its fibers irrigated by bloud 6. An objection answer'd against the former doctrine 7. The circulation of the bloud and other effects that follow the motion of the heart 8. Of Nutrition 9. Of Augmentation 10. Of death and sickness CHAP. XXVII Of the motions of Sense and of the Sensible Qualities in gegeral in particular of those which belong to Touch Tast and Smelling 1. The connexion of the subsequent Chapters with the precedent 2. Of the senses and sensible qualities in general And of the end for which they serve 3. Of the sense of touching and that both it and its qualities are bodies 4. Of the tast and its qualities that they are bodies 5. That the smell and its qualities are real bodies 6. Of the conformity betwixt the two senses of smelling and tasting 7. The reason why the sense of smelling is not so perfect in man as in beasts with a wonderful history of a man who could wind sent as well as any beast CHAP. XXVIII Of the sense of Hearing and of the sensible quality Sound 1. Of the sense of hearing and that sound is purely motion 2. Of divers arts belonging to the sense of hearing all which confirm that sound is nothing but motion 3. The same is confirmed by the effects caused
oftentimes works strange effects in their issue 4. Of Antipathies 5. Of Sympathies 6. That the Antipathy of beasts towards one another may be taken away by assuefaction 7. Of longing marks seen in children 8. Why divers men hate some certain meats particularly Cheese 9. Concerning the providence of Ants in laying up in store for winter 10. Concerning the foreknowing of beasts The Conclusion of the first Treatise TABLE Of the Second TREATISE CONCERNING Mans Soul PREFACE CHAP. I. OF simple Apprehensions 1 what is a right apprehension of a thing 2. The very thing it self is truly in his understanding who rightly apprehends it 3. The apprehensions of things coming to us by our senses are resolvable into other more simple apprehensions 4. The apprehension of a Being is the most simple and Basis of all the rest 5. The apprehension of a thing is in next degree to that of Being and it is the Basis of all the subsequent ones 6. The apprehension of things known to us by our senses consists in certain respects betwixt two things 7. Respect or relation hath not really any formal being but only in the apprehension of man 8. That Existence or Being is the proper affection of man and that mans soul is a comparing power 9. A thing by coming into the understanding of man loses nothing of its own peculiar nature 10. A multitude of things may be united in mans understanding without being mingled or confounded together 11. Of abstracted and concrete terms 12. Of universal notions 13. Of apprehending a multitude under one notion 14. The power of the understanding reaches as far as the extent of Being CHAP. II. Of thinking and knowing 1. How a judgment is made by the understanding 2. That two or more apprehensions are identified in the soul by uniting them in the stock of being 3. How the notions of a substantive an adjective are united in the soul by the common stock of being 4. That a setled judgment becomes a part of our soul. 5. How the soul comes to deem or settle a judgment 6. How opinion is begotten in the understanding 7. How faith is begotten in the unstanding 8. Why truth is the perfection of a reasonable Soul and why it is not found in simple apprehensions as well as in Enuntiations 9. What is a solid judgment and what a slight one 10. What is an acute judgment and what a dull one 11. In what consists quickness and clearness of judgment and their opposite vices CHAP. III. Of Discoursing 1. How discourse is made 2. Of the figures and moods of syllogisms 3. That the life of man as man consists in discourse and of the vast extent of it 4. Of humane actions and of those that concern our selvs 5. Of humane actions as they concern our neighbours 6. Of Logick 7. Of Grammar 8. Of Rhetorick 9. Of Poetry 10. Of the power of speaking 11. Of arts that concern dumb and insensible creatures 12. Of Arithmetick 13. Of Prudence 14. Observations upon what has been said in this Chapter CHAP. IV. How a Man proceeds to Action 1. That humane actions proceed from two several principles understanding and sense 2. How our general and inbred maximes concur to Humane Actions 3. That the rules and maximes of arts works positively in us though we think not of them 4. How the understanding casts about when it wants sufficient grounds for action 5. How reason rules over sense and passion 6. How we recall our thoughts from distractions 7. How reason is sometimes overcome by sense and passion CHAP. V. Containing proofs out of our Single apprehensions that our Soul is Incorporeal 1. The connexion of the subsequent Chapters with the precedent 2. The existence of corporeal things in the soul by the power of apprehension proves her to be immaterial 3. The notion of Being which is innate in the Soul proves the same 4. The same is proved by the notion of respects 5. That corporeal things are spiritualized in the understanding by means of the souls working in and by respects 6. That the abstracting of Notions from all particular and individual accidents proves the the immateriality of the soul. 7. That the universality of abstracted notions proves the same 8. That collective apprehensions proves the same 9. The operations of the soul drawing always from multitude to unity prove the same 10. The difference betwixt the notion of a thing in our understanding and the impression that corresponds to the same thing in our phansie proves the same 11. The apprehension of negations and privations proves the same CHAP. VI. Containing proofs out of our souls operations in knowing or deeming any thing that she is of a spiritual nature 1. The manner of judging or deeming by apprehending two things to be identified proves the soul to be immaterial 2. The same is proved by the manner of apprehending opposition in a negative judgment 3. That things in themselvs opposite to one another having no opposition in the soul proves the same 4. That the first truths are identified to the soul. 5. That the soul hath an infinite capacity and consequently is immaterial 6. That the opposition of contradictory propositions in the soul proves her immateriality 7. How propositions of eternal truth prove the immateriality of the soul. CHAP. VII That our Discoursing proves our Soul to be incorporeal 1. That in discoursing the soul contains more in it at the same time than is in the phantasy which proves her to be immaterial 2. That the nature of discourse proves the soul to be order'd to infinite knowledge and consequently immaterial 3. That the most natural objects of the soul are immaterial and consequently the soul her self is such CHAP. VIII Cantaining proofs out of our manner of proceeding to action that our Soul is incorporeal 1. That the souls being a power to order things proves her to be immaterial 2. That the Souls being able to move without being moved proves her to be immaterial 3. That the souls proceeding to action with an universality and indifferency proves the same 4. That the quiet proceeding of reason proves the same 5. A conclusion of what hath been said hitherto in this second Treatise CHAP. IX That our soul is a Substance and Immortal 1. That Mans soul is a substance 2. That man is compounded of some other substance besides his body 3. That the Soul subsists of it self independently of the body 4. Two other arguments to prove the same one positive the other negative 5. The same is proved because the soul cannot be obnoxious to the cause of mortality 6. The same is proved because the Soul hath no contrary 7. The same is proved from the end for which the Soul was created 8. The same is proved because she can move without being moved 9. The same is proved from her manner of operation which is grounded in being 10. Lastly it is proved from the science of Morality the principles wherof would be destroyed
if the soul were mortal CHAP. X. Declaring what the Soul of a man separated from his body is and of her knowledg and manner of working 1. That the Soul is one simple knowing act which is a pure substance and nothing but substance 2. That a separated Soul is in no place and yet is not absent from any place 3. That a separated Soul is not in time nor subject to it 4. That the Soul is an active substance and all in it is activity 5. A description of the Soul 6. That a separated Soul knows all that which she knew whilst she was in her body 7. That the least knowledge which the Soul acquires in her body of any one thing causes in her when she is separated from her body a complete knowledge of all things whatever 8. An answer to the objections of some Peripateticks who maintain the Soul to perish with the body 9. The former Peripateticks refuted out of Aristotle 10. The operations of a separated soul compared to her operations in her body 11. That a separated soul is in a state of pure being and consequently immortal CHAP. XI Shewing what effects the divers manners of living in ths world do cause in a soul after she is separated from her body 1. That a Soul in this life is subject to mutation and may be perfected in knowledge 2. That the knowledge which a soul gets in this life will make her knowledge in the next life more perfect and firm 3. That the soul of men addicted to science whilest they lived here are more perfect in the next world than the souls of unlearned men 4. That those souls which embrace virtue in this world will be most perfect in the next and those which imbrace vice most miserable 5. The state of a vitious soul in the next life 6. The fundamenatl reason why as well happiness as misery is so excessive in the next life 7. The reason why mans soul requires to be in a body and to live for some space of time joyn'd with it 8. That the misery of the soul in the next world proceeds out of the inequality and not out of the falsity of her judgments CHAP. XII Of the perseverance of a soul in the state she finds her self in at her first separation from her body 1. The explication and proof of that maxime that If the cause be in act the effect must also be 2. The effects of all such agents as work instantaneously are complete in the first instant that the agents are put 3. All pure spirits work instantaneously 4. That a soul separated from her body cannot suffer any change after the first instant of her separation 5. That temporal sins are justly punished with eternal pains The Conclusion Preface THis Writing was design'd to have seen the light under the name of One Treatise But afer it was drawn in Paper as I cast a view over it I found the Proaemial part which Treats of Bodies so ample in respect of the other which was the End of it and for whose sake I medled with it that I readily apprehended my Reader would think I had gone much astray from my Text when proposing to speak of the Immortality of Mans Soul three parts of four of the whole Discourse should not so much as in one word mention that Soul whose nature and proprieties I aim'd at the discovery of To avoid this incongruity occasioned me to change the Name and Unity of the Work and to make the survay of Bodies a body by it self though subordinate to the Treatise of the Soul Which notwithstanding it be less in bulk than the other yet I dare promise my Reader that if he bestow the painsr equisite to perfect himself in it he will find as much time well spent in the due reading of it as in the reading of the former Treatise though far more large But I discern an Objection obvious to be made or rather a Question Why I should spend so much time in the consideration of Bodies wheras none that has formerly written of this Subject has in any measure done the like I might answer that they had on other occasions first written of the nature of Bodies as I may instance in Aristotle and sundry others who either have themselvs professedly treated the Science of Bodies or have supposed that part sufficiently perform'd by other pens But truly I was by an unavoidable necessity hereto obliged which is a current of doctrin that at this day much reigns in the Christian Schools where Bodies and their overations are explicated after the manner of spiritual things For we having very slender knowledge of Spiritual Substances can reach no further into their nature than to know that they have certain Powers or Qualities but can seldom penetrate so deep as to descend to the particulars of such Qualities or Powers Now our Modern Philosophers have introduced such a course of learning into the Schools that to all questions concerning the proper natures of Bodies and their operations 't is held sufficient to answer they have a Quality or a Power to do such a thing And afterwards they dispute whether this Quality or Power be an Entity distinct from its subject or no and how it is separable or unseparable from it and the like Consormable to this who will look into the Books which are in vogue in these Schools shall find such Answers and such controversies every where and few others As of the Sensible Qalities ask what it is to be white or red what to be sweet or sowr what to be odoriferous or stinking what to be cold or hot And you are presently paid with that it is a Sensible Quality which has the power to make a Wall white or red to make a Meat agreeable or disagreeable to the tast to make a grateful or ungrateful Smell to the nose c. Likewise they make the same Questions and Resolutions of Gravity and Levity as whether they be qualities that is Entities distinct from their subjects and whether they be active or passive which when they have disputed slightly and in common with Logical arguments they rest there without any further searching into the Physical causes or effects of them The like you shall find of all strange Effects of them The Loadstone and Electrical bodies are produced for miraculous and not understandable things and which must be acknowledg'd to work by hidden Qualities that mans wit cannot reach to And ascending to Living Bodies they give it for a Maxim that Life is the action of the same Entity upon it self that Sense is likewise a work of an intrinsecal power in the part we call Sense upon it self Which our predecessors held the greatest absurdities that could be spoken in Philosophy Even some Physicians that take upon them to teach the curing of our Bodies often pay us with such terms among them you have long discourses of a retentive of an expulsive of a purging of a consolidating Faculty
will pierce cut out the water almost into as little parts as themselves and mingling themselves with them they will flie away together and so convert the whole body of water into subtile smoke whereas the same Agent after long working upon lead will bring it into no less parts then small grains of dust which it calcines it into And gold that is more dense then lead resists peremptorily all the dividing power of fire and will not at all be reduced into a calx or lime by such operation as reduced lead into it So that remembring how the nature of Quantity is Divisibility and considering that rare things are more divisible then dense ones we must needs acknowledge that the nature of Quantity is some way more perfectly in things that are Rare then in those that are Dense On the other side more compacted and dense things may haply seem to some to have more Quantity then those that are rare and that is but shrunk together which may be stretch'd out and driven into much greater dimensions then the Quantity of rare things taking the quantities of each equal in outward appearance As gold may be beaten into much more and thiner leaf then an equal bulk of silver or lead A wax candle will burn longer with a small light then a tallow candle of the same bigness and consequently be converted into a greater quantity of fire and air Oyl will make much more flame then spirit of wine that is far rarer then it These and such like considerations have much perplex'd Philosophers and driven them into diverse thoughts to find out the reasons of them Some observing that the dividing of a body into little parts makes it less apt to descend then when it is in greater have believ'd the whole cause of lightness and rarity to be derived from division As for example they find that lead cut into little pieces will not go down so fast in water as when it is in bulk and it may be reduced into so smal atomes that it will for some space swim upon the water like dust of wood Which assumption is prov'd by the great Galileus to whose excellent wit and admirable industry the world is beholding not only for his wonderful discoveries made in the Heavens but also for his acurate and learned declaring of those very things that lye under our feet He about the 90. page of his first Dialogue of Motion clearly demonstrates how any real medium must of necessity resist more the descent of a little piece of lead or any other weighty matter than it would a greater piece and the resistance will be greater and greater as the pieces are lesser and lesser So that as the pieces are made less they will in the same medium sink the flower and seem to have acquired a new nature of lightness by the diminution not only of having less weight in them than they had as half an ounce is less than a whole ounce but also of having in themselvs a less proportion of weight to their bulk than they had as a pound of Cork is in regard of its magnitude lighter than a pound of Lead So as they conclude that the thing whose continued parts are the lesser is in its own nature the lighter and the rarer and other things whose continued parts are greater be heavier and denser But this discourse reaches not home for by it the weight of any body being discovered by the proportion it has to the medium in which it descends it must ever suppose a body lighter than it self in which it may sink and go to the bottome Now of that lighter body I enquire what makes it be so and you must answer by what you have concluded that it is lighter then the other because the parts of it are lesse and moreseverd from one another for if they be as close together their division avails them nothing since things sticking fast together work as if they were but one and so a pound of lead though it be filed into small dust if it be compacted hard together will sink as fast as if it were one bulk Now then allowingthe little parts to be seperated I ask what other body fills up the spaces between those little parts of the medium in which your heavy body descends For if the parts of water are more sever'd then the parts of lead there must be some other substance to keep the parts of it asunder let us suppose this to be air and I ask Whether an equal part of air be as heavy as so much water or whether it be not If you say it is then the compound of water and air must be as heavy as lead since their parts one with another are as much compacted as the parts of lead are For there is no difference whether those bodies whose little parts are compacted together be of the same substance or of divers or whether the one be divided into smaller parts then the other or not so they be of equal weights in regard of making the whole equally heavy as you may experience if you mingle pin-dust with a sand of equal weight though it be beaten into far smaller divisions then the pin-dust and put them in a bag together But if you say that air is not so heavy as water it must be because every part of air hath again its parts more sever'd by some other body then the parts of water are sever'd by air And then I make the same instance of that body which severs the parts of air And so at last since there cannot actually be an infinite process of bodies one lighter then another you must come to one whose little parts filling the pores and spaces between the parts of the others have no spaces in themselves to be fil'd up But as soon as you acknowledge such a body to be lighter and rarer then all the rest you contradict and destroy all you said before For by reason of its having no pores it follows by your rule that the little parts of it must be as heavy if not heavier then the little parts of the same bigness of that body whose pores it fills and consequently it is proved by the experience we alledg'd of pin-dust mingled with sand that the little parts of it cannot by their mingling with the parts of the body in which it is immediately contain'd make that lighter then it would be if these little parts were not mingled with it Nor would both their parts mingled with the body which immediately contains them make that body lighter And so proceeding on in the same sort through all the mingled bodies till you come to the last that is immediately mingled with water you will make water nothing the lighter for being mingled with all these and by consequence it should be as heavy and as dense as lead Now that which deceiv'd the Authors of this opinion was that they had not a right intelligence of the causes
which made little parts of bodies naturally heavie descend slowly in regard of the velocity of greater parts of the same bodies descending the Doctrine of which we intend to deliver hereafter Others therfore perceiving this rule to fall short have indeavour'd to piece it out by the mixtion of Vacuitie among bodies believing it is that which makes one rarer then another Which mixtion they do not put always immediate to the main body they consider but if it have other rarer and lighter bodies mingled with it they conceive this mixtion immediate only to the rarest or lightest As for example a Crystal being lighter and consequently rarer then a Diamond they will not say there is more vacuity in a Crystal then in a Diamond but that the pores of a Crystal are greater and consequently there is more aire in a Crystal to fil the pores of it then is in a Diamond and the vacuities are in the aire which abounding in a Crystal more then in a Diamond makes that lighter and rarer then this by the more vacuites that are in the greater Quantity of aire which is mingled with it But against this suppsition a powerful adversary is urged for Aristotle in his 4. Book of Physicks hath demonstrated that there can be no motion in vacuity 'T is true they indeavour to evade his demonstration as not reaching home to their supposition by acknowledging it to be an evident one in such a vacuity as he there speaks of which he supposed so great that a body may swim in it as in an Ocean and not touch or be near any other body whereas this opinion exclude all such vast inanity admit no vacuities but so little ones as no body whatever can come to but wil be biger than they and consequently must on some side orother touch the corporal parts which those vacuities divide for they are the separations of the least parts that are or can be actually divided from one another which parts must of necessity touch one another on some side or else they could not hang together to compose one substance and and therefore the dividing vacuities must be less then the divided parts And thus no body will ever be in danger of floating up and down without touching any thing which is the difficulty that Aristotle chiefly impugns I confess I should be very glad that this supposition might serve our turne and save the Phenomena that appear among bodies through their variety of Rarity and Density Which if it might be then would I straight go on to the inquiring after what follow'd out of this ground as Astronomers to use our former similitude calculate the future appearances of the Celestial bodies out of those motions and orbs they assign to the Heavens For as this apprehension of vacuity in bodies is very easie and intelligible so the other which I conceive to be the truth of the case is exceedingly abstracted and one of the most difficult points in all the Metaphysicks and therefore I would if it were possible avoid touching upon it in this discourse which I desire should be as plain and easie and as much removed from Scholastick terms as may be But indeed the inconveniences that follow out of this supposition of vacuities are so great as it is impossible by any means to slide them over As for example let us borrow of Gallileus the proportion of weight between water and air He shews us how the one is 400 times heavier then the other And Marinus Ghetaldus teaches us that gold is 19 times heavier then water so that gold must be 7600 times heavier then air Now then considering that nothing in a body can weigh but the solid parts of it it follows that the proportion of the parts of gold in a sphere of an inch Diameter is to the parts of the air of a like dimension as 7600 is to one Therfore in air it self the vacuities that are supposed in it will be to the solid parts of it in the same proportion as 7600 to one Indeed the proportion of difference shal be greater for even in gold many vacuities must be admitted as appears by the heating of it which shews that in every least part it is exceeding porous But according to this rate without pressing the inconvenience any further the air will by this reckoning appear to be like a net whose holes distances are to the lines and threds in the proportion of 7600 to one and so would be lyable to have little parts of its body swim in those greater vacuities contrary to what they strive to avoid Which would be excedingly more if we found on the one side any bodies heavier denser then gold that were so solid as to exclude all vacuities on the other side should balance them withsuch bodies as are lighter and rarer then air as fire is and as some say will have the aether to be But already the disproportion is so great and the vacuity so strangely exceeds the body in which it is as were too great an absurdity to be admitted And besides it would destroy all motion of small bodies in the air if it be true as Aristotle hath demonstrated in the fourth Book of his Physicks that motion cannot be made but among bodies and not in vacuo Again if rarity were made by vacuity rare bodies could not be gather'd together without losing their rarity and becoming dense The contrary of which we learn by constant experience as when the Smith and Glassemender drive their white and fury fires as they term them when aire pierces most in the sharp wind and generally we see that more of the same kind of rare bodies in less place works more efficaciously according to the nature that results out of that degree of rarity Which argues that every little part is as rare as it was before for else it would lose the vertue of working according to the nature but that by their being crowded together they exclude all other bodies that before mediated between the little parts of their main body and so more parts being gotten together in the same place then formerly there were they work more forcibly Thirdly if such vacuities were the cause of rarity it would follow that fluid bodies being rarer then solid ones would be of themselvs standing like nets or cobwebs wheras contrariwise we see their natures are to run together and to fill up every little creek and corner which effect following out of the very nature of the things themselves needs must exclude vacuities out of that nature And lastly if it be true as we have shew'd in the last Chapter that there are no actual parts in Quantity it follows of necessity that all Quantity must of it self be one as Metaphysicks teach us and then no distance can be admitted between one Quantity and another And truely if I understand Aristotle right he hath perfectly demonstrated that no vacuity is possible in nature
because mans discerning them to be able to discourse accordingly of them is the princpal respect for which their denominations are to be allotted them we may with reason call those things dense wherein a man finds a sensible difficulty to part them and those rare where the resistance is imperceptible And to these two notions of rarity and density we must allow a great latitude far from consisting in an indivisible state for since rare faction makes a lesser body equal to a bigger and all inequalitie betwixt two bodies has the conditions of a Body it follows that the excess of one body over another consists of infinite parts into which it might be divided and consequently that what is rarified passes as many degrees as the inequality or excess hath parts And the same law being in condensations both dense and rare things must be acknowledg'd capable of infinite variety and diversity of states in regard of more and less in the same kind These things being premised and calling to mind that 't is the nature of density to make the parts of a dense thing compact and stick together and be hardly divisible and on the contrary side that 't is the nature of rarity to diffuse and extend a rare thing and prepare and approach it to division according to the proportion of the degree of rarity which it has and that weight abounds where there is excess of density and is very little or none in excess of rarity we may now begin in our imagination to put these Qualities into the scales one against another to see what effects they produce in Bodies And first let us weigh Gravity against Density or sticking together of parts which sticking or compactedness being natural to density requires some excess of gravity in proportion to the density or some other outward violence to break it If then in a dense body the gravity overcome the density and make the parts of it break asunder it will draw them downwards towards the center that gravity tends to and never let them rest till they come thither unless some impediment meet them by the way and stop their journey so that such a body will as near as it possibly can lie in a perfect spherical figure in respect of the center and the parts of it will be chang'd and alter'd and thrust on any side that is the ready way thither the force of gravity therefore working upon it it will run as far as it meets with nothing to hinder it from attaining this spherical superficies Wherefore such bodies for the most part have no setled outside of their own but receive their figure and limits from such lets as hinder them from attaining to that sphericalness they aim at Now Aristotle whose definitions are in these matters generally receiv'd as fully expressing the notions of mankind tells us and our own experience confirms it that we use to call those things moist which run in such sort as we have here set down and that we term those things dry which have a Consistence within themselves and which to enjoy a determinate figure do not require the stop or hinderance of another body to limit and circle them in which will be the nature of those that have a greater proportion of density in respect of their gravity And thus out of the comparison of density with weight we have found two more qualities then we yet had met withall namely wetness and dryness For though a body be dense which of its own nature singly considered would preserve the continuity of its parts as making the body hardly divisible whereby it would be dry yet if the gravity that works upon it be in proportion greater then the density it will sever the parts of it and make them run to the center and so become fluide and moist though not in the eminentest degree that may be of fluidity and moisture because that if the like over proportion of gravity happen in a rare body it will there more powerfully work its effect then it can in a dense body because a rare body will more easily obey and yield to the gravity that masters it then a dense one will and consequently will be more fluide and moist then it Now on the other side in weighing Rarity against Gravity if it happen that the Rarity overcome the Gravity then the gravity will not change the figure of a body so proportion'd but what figure it has from its proper natural causes the same will still remain with it and consequently such a body will have terms of its own and not require an ambient body to limit and circle it in which nature we call dry But if the proportion of the gravity be the greater and overcome the rarity then by how much the rarity is greater so much the more will the gravity force it to apply it self equally and on all sides to the center and such a body will the more easily receive its figure from another and will be less able to consist of it self which properties we attribute to wetness or moisture So that it appears how the qualities of wet and dry which first we found in things that were dense are also common to that nature of bodies which we term rare And thus by our first inquiry after what kind of bodies result out of the compounding of rarity and density with gravity we discover four different sorts some dense ones that are dry and others likewise dense that are moist then again some rare ones that are likewise moist and other rare ones that are dry But we must not rest here let us proceed a little further to search what other properties these four kinds of bodies will have which we shall best discover if we apply them severally to some other compounded bodie of which nature are all those we converse with or see and then consider the effects which these work upon it To begin with that which we said is so excessively Rare that gravity has no power over it If we look on the multitude of little parts it may be divided into whereof every one will subsist by it self for we have already proved it dry and then suppose them to be moved with force and strength against the body we apply them to it must necessarily follow that they will forcibily get into the porousness of it and pass with violence between part and part and of necessity separate the parts of that thing one from another as a knife or wedge doth a solid substance by having their thinnest parts press'd into it So that if in the compounded thing some parts be more weighty others more light as of necessity there must be the heaviest will all fall lowest the lightest will fly uppermost and those which are of a mean nature between the two extremes will remain in the middle In summe by this action an extreme rare body upon a compounded one all the parts of one kind that were in the
the operation of the understanding is nothing else but the inward superficies of a body that compasses and immediately conteines another Which ordinarily being of a rare body that doth not shew it self to us namely the Air is for the most part unknown by us But because nothing can make impression on our minds and cause us to give it a name otherwise then by being known therfore our understanding to make a compleat notion must add something else to this fleeting and unremarkable Superficies that may bring it to our acquaintance And for this end we may consider further that as this Superficies hath in it self so the bodie enclosed in it gains a certain determinate respect to the stable and immoveable bodies that environ it As for example we understand such a Tree to be in such a place by having such and such respects to such a Hill near it or to such a House that stands by it or to such a River that runs under it or to such an immoveable point of the Heaven that from the Suns rising in the Equinox is called East and such like To which purpose it imports not whether these that we call immoveable bodies and points be truly so or do but seem so to mankind For man talking of things according to the notions he frames of them in his mind speech being nothing else but an expression to another man of the images he hath within himself and his notions being made according to the seeming of the things he must needs make the same notions whether the things be truly so in themselvs or but seem to be so when that seeming or appearance is always constantly the same Now then when one body dividing another gets a new immediate clothing and consequently new respects to the stable and immoveable bodies or seeming such that environ it we vary in our selves the notion we first had of that thing conceiving it now accompanied with other circumstances and other respects then formerly it had Which notion we express by saying it has changed its place and is now no longer where it was at the first And this change of place we call Locall motion to wit the departing of a body from that hollow superficies which inclosed it and its changing to another wherby it gains new respects to those parts of the World that have or in some sort may seem to have immobility and fixed stableness So as hence 't is evident that the substance of Locall motion consists in Division and that the alteration of Locality follows Division in such sort as the becoming like or unlike of one wall to another follows the action whereby one of them becomes white And therefore in Nature we are to seek for any entity or special cause of applying the moved body to a place as place which is but a respect consequent to the effect of division but only to consider what real and physical action unites it to that other body which is called its place and truly serves for that effect And consequently they who think they have discover'd a notable subtilty by bringing in an Entity to unite a Body to its Place have strain'd beyond their strength and grasped but a shadow Which will appear yet more evident if they but mark well how nothing is divisible but what of it self abstracting from division is one For the nature of Division is the making of many which implies that what is to be divided must of necessity be not-many before it be divided Now Quantity being the subject of division 't is evident that purely of it self and without any force or adjoyned helps it must needs be one wherever some outward agent doth not introduce multiplicity upon it And whenever other things work upon quantity as quantity it is not the nature and power of their operation to produce unity in it and make it one for it is already one but contrariwise the immediate necessary effect that flows from them in this case is to make one quantity many according to the circumstances that accompany the divider and that which is to be divided And therefore although we may seek causes why some one thing sticks faster together then some other yet to ask absolutely why a body sticks together were prejudicial to the nature of quantity whose essence is to have parts sticking together or rather to have such unity as without which all divisibility must be excluded Out of which discourse it follows that in local motion we are to look onely for a cause or power to divide but not for any to unite For the very nature of quantity unites any two parts that are indistant from one another without needing any other cement to glue them together as we see the parts of water and all liquid substances presently unite themselves to other parts of like bodies when they meet with them and to solid bodies if they chance to be next them And therefore 't is vain to trouble our heads with Unions and imaginary Moods to unite a body to the place it is in when their own nature makes them one as soon as they are immediate to each other And accordingly if when we see a Boul move we would examine the causes of that motion we must consider the quantity of air or water it makes to break from the parts next to it to give place to it self and not speculate upon an intrinsecall relation from the body to a certain part of the imaginary space they will have to run through all things And by ballancing that quantity of air or water which it divides we may arrive to make an estimate of what force the Boul needs to have for its motion Thus having declar'd that the locality of motion is but an extrinsecall denomination and no reality in the thing moved we may now cast an eye upon a vast consequence that may be deduced out of what we have hitherto said For if we consider the nature of a Body that is that a Body is a Body by quantity and that the formall notion of Quantity is nothing else but Divisibility and that the adequate Act of Divisibility is Division 't is evident there can be no other Operation upon Quantity nor by consequence among Bodies but must either be such Division as we have here explicated or what must necessarily follow out of such division And Division as we have even now explicated being Locall Motion 't is evident that All operations among Bodies are either Local Motion or such as follow out of Local motion Which conclusion however unexpected and at first hearing appearing a Paradox will nevertheless by the ensuing work receive such evidence as it it cannot be doubted of and that not only by force of argumentation and by necessity of notions as is already reduced but also by experience and declaratiosns of particulars as they shall occur But now to apply what we have said to our proposed subject 't is obvious to every
man that seeing the Divider is the agent in division and in Local motion and dense bodies are by their nature dividers the Earth must in that regard be the most active among the Elements since it is the most dense of them all But this seems to be against the Common judgment of all the searchers of nature who unamimously agree that Fire is the most active Element As also it seems to impugne what we our selves have determin'd when we said there were two active qualities heat and cold whereof the first was in its greatest excess in Fire and the latter in water To reconcile these we are to consider that the action of Cold in its greatest height is composed of two parts the one is a kind of pressing and the other is penetration which requires applicability Of which two the former arises out of density but the latter out of moderation of density as I have declared in the precedent Chapter Wherefore the former will exceed more in Earth though the whole be more eminent in Water For though considering only the force of moving which is a a more simple and abstracted notion then the determination and particularization of the Elements and is precedent to it therein Earth hath a precedency over water yet taking the action as it is determin'd to be the action of a particular Element and as it concurs to the composition or dissolution of mixed bodies in that consideration which is the chief work of Elements and requires an intime application of the Agents Water hath the principality and excess over Earth As for Fire it is more active then either of them as will appear clearly if we consider how when Fire is applyed to fewel and the violence of blowing is added to its own motion it incorporates it self with the fewel and in a small time converts a great part of it into its own nature and shatters the rest into smoak and ashes All which proceeds from the exceeding smallness and dryness of the parts of fire which being moved with violence against the fewel and thronging in multitudes upon it easily pierce the porous substance of it like so many extreme sharp Needles And that the force of Fire is as great and greater then of Earth we may gather out of our former discourse where having resolved that density is the virtue by which a body is moved and cuts the medium and again considering that celerity of motion is a kind of density as we shall by and by declare 't is evident that since blowing must of necessity press violently and with a rapid motion the parts of fire against the fewel and so condense them exceedingly there both by their celerity by bringing very many parts together there it must needs also give them activity and vertue to pierce the body they are beaten against New that Celerity is a kind of Density will appear by comparing their natures For if we consider that a dense body may be dilated so as to possess and fill the place of a rare body that exceeded it in bigness and by that dilatation may be divided into as many and as great parts as the rare body was divisible into we may conceive that the substance of those parts was by a secret power of nature folded up in that little extension in which it was before And even so if we reflect upon two Rivers of equal channels and depths whereof the one goes swifter then the other and determine a certain length of each channel and a common measure of Time we shall see that in the same measure of time there passes a greater bulk of water in the designed part of the channel of the swifter stream then in the designed part of the flower though those parts be equal Nor imports it that in Velocity we take a part of time whereas in Density it seems that an instant is sufficient and consequently there would be no proportion between them For knowing Philosophers all agree that there are no Instants in time and that the apprehension of them proceeds meerly from the manner of our understanding And as for parts in time there cannot be assumed any so little in which the comparison is not true and so in this regard it is absolutely good And if the Reader have difficulty at the disparity of the things which are pressed together in Density and in Celerity for that in Density there is only Substance in Celerity there is also Quantity crowded up with the substence he will soon receive satisfaction when he shall consider that this disparity is to the advantage of what we say and makes the nature of density more perfect in celerity and consequently more powerful in fire then in earth Besides if there were no disparity it would be a distinct species of density but the very same By what we have spoken above it appears how fire gets into fewel now let us consider how it comes out for the activity of that fierce body will not let it lie still and rest as long as it has so many enemies round about it to rouse it up We see then that as soon as it has incoporated it self with the fewel and is grown master of it by introducing into it so many of its own parts like so many Souldiers into an Enemies Town they break out again on every side with as much violence as they came in For by reason of the former resistance of the fewel their continual streaming of new parts upon it and one overtaking another there where their journey was stop'd all which is increas'd by the blowing doth so exceedingly condense them into a narrower room then their nature effects that as soon as they get liberty and grow masters of the fewel which at the first was their prison they enlarge their place and consequently come out and flie abroad ever aiming right forwards from the point where they begin their journey for the violence wherewith they seek to extend themselves into a larger room when they have liberty to do so will admit no motion but the shortest which is by a straight line So that if in our phantasie we frame an image of a round body all of fire we must withall presently conceive that the flame proceeding from it would diffuse it self every way indifferently in straight lines so that the source serving for the Center there would be round about it an huge Sphere and of fire and light unless some accidental and extern cause should determine its motion more to one part then to another Which compass because it is round and has the figure of a Sphere is by Philosophers term'd the Sphere of its activity So that it is evident the most simple and primary motition of fire is a flux in a direct line from the center of it to its circumference taking the fewel for its center as also that when 't is beaten against a harder body it may be able to destroy it though that
conceive let us go on to the fourth which requires that we satisfie their inquisition who ask what becomes of that vast body of shining light if it be a body that fills all the distance between heaven and earth and vanishes in a moment assoon as a cloud or the Moon interposes it self between the Sun and us or that the Sun quits our Hemisphere No sign at all remains of it after its extinction as doth of all other substances whose destruction is the birth of some new thing Whither then is it flown we may be perswaded that a mist is a corporeal substance because it turns to drops of water upon the twigs that it invirons and so we might believe light to be fire if after the burning of it out we found any ashes remaing but experience assures us that after it is extinguished it leaves not the least vestigium behind it of having been there Now before we answer this objection we will intreat our Adversary to call to mind how we have in our solution of the former declared and proved that the light which for example shines from a candle is no more then the flame is from whence it springs the one being condensed and the other dilated and that the flame is in a perpetual flux of consumption about the circumference and of restauration at the center where it sucks in the fewell and then we will enquire of him what becomes of the bodie of flame which so continually dies and is renewed and leaves no remainder behind it as well as he doth of us what becomes of our body of light which in like manner is alwaies dying and alwaies springing fresh And when he hath well considered it he will find that one answer will serve for both Which is That as the fire streams out from the fountain of it and growes more subtile by its dilatation it sinks the more easily into those bodies it meets withall the first of which and that environs it round about is aire With air then it mingles and incorporates it self and by consequence with the other little bodies that are mingled with the aire and in them it receives the changes which nature works by which it may be turn'd into the other Elements if there be occasion or be still conserv'd in bodies that require heat Upon this occasion I remember a rare experiment that a Noble-Man of much sincerity and a singular friend of mine told me he had seen which was That by meanes of glasses made in a very particular manner and artificially placed one by another he had seen the Sun-beams gather'd together and precipitated down into a brownish or purplish red powder There could be no fallacy in this operation for nothing whatever was in the glasses when they were placed and disposed for this intent and it must be in the hot time of the year else the effect would not follow And of this Magistry he could gather some dayes near two ounces in a day And it was of a strange volative nature and would pierce and imprint his spiritual quality into gold it self the heaviest and most fixed body we converse withall in a very short time If this be plainly so without any mistaking then mens eyes and hands may tell them what becomes of light when it dies if a great deal of it were swept together But from what cause soever this experience had its effect our reason may be satisfied with what we have said above for I confesse for my part I beleeve the appearing body might be something that came along with the Sun-beams and was gather'd by them but not ther pure substance Some peradventure will object those lamps which both ancient and modern writers have reported to have been found in Tombes and Urns long time before closed up from mens repair to them to supply them with new fewel and therefore they believe such fires to feed upon nothing and consequently to be inconsumptible and perpetual Which if they be then our doctrine that will have light to be nothing but the body of fire perpetually flowing from his center and perpetual dying cannot be sound for in time such fires would necessarily spend themselves in light although light be so subtile a substance that an exceeding little quantity of fewel may be dilated into a vast quantity of light However there would be some consumption which how imperceptible soever in a short time yet after a multitude of revolutions of years must needs discover it self To this I answer That for the most part the witnesses who testifie originally the stories of these lights are such as a rational man cannot expect from them that exactness or nicitie of observation which is requisite for our purpose For they are usually gross labouring people who as they dig the ground for other intentions Stumble upon these Lamps by chance before they are aware and commonly they break them in the finding and imagine they see a glimpse of light which vanishes before they can in a manner take notice of it and is peradventure but the glistering of the broken glass or glazed pot which reflects the outward light assoon as by rummaging in the ground and discovering the Glass the light strikes upon it in such manner as sometimes a Diamond by a certain incountring of light in a dusky place may in the first twinkling of the motion seem to sparkle like fire And afterwards when they shew their broken Lamp and tell their tale to some man of a pitch of wit above them who is curious to inform himself of all the circumstances that may concern such lights they strain their memory to answer him satisfactorily unto all his demands and thus for his sake they perswade themselves to remember what they never saw and he again on his side is willing to help out the story a little And so after a while a very formal and particular relation is made of it As happens in like sort in reporting of all strange and unusual things when even those that in their nature abhor from lying are naturally apt to strain a little and fashion up in a handsome mould and almost to perswade themselves they saw more then they did so innate it is to every man to desire the having of some preeminence beyond his neighbours be it but in pretending to have seen something which they have not Therefore before I engage my self in giving any particular answer to this objection of pretended inconsumptible lights I would gladly see the effect certainly averred and undoubtedly proved For the testemonies which Fortunius Licetus produces who has been very diligent in gathering them and very sub 〈◊〉 in discoursing upon them and as the exactest Author that has written upon this subject do not seem to me to make that certainty which is required for the establishing of a ground in Philosophy Nevertheless if there be any certain experience in this particular I should think there might be some Art by circulation
they are moved be greater then the distance of the greater weight from the same point For 't is plain that the weight which is more distant must be moved a greater space then the nearer weight in the proportion of the two distances Wherfore the force moving it must carry it in a velocity of the said proportion to the velocity of the other And consequently the Agent or mover must be in that proportion more powerfull then the contrary mover And out of this practise of Geometricians in Mechanicks which is confirmd by experience 't is made evident that if other conditions be equal the excess of so much Gravity will make so much Velocity and so much velocity in proportion will recompence so much gravity Out of the precedent Conclusions another follows which is that nothing receds from quiet or rest and attains a great degree of Celerity but it must pass through all the degrees of Celerity that are below the obtain'd degree And the like is in passing from any lesser degree of velocity to a greater because it must pass through all the intermediate degrees of velocity For by the declaration of velocity which we have even now made we see that there is as much resistance in the Medium to be overcome with speed as there is for it to be overcome in regard of the quantity or line of extent of it because as we have said the force of the Agent in counterpoises ought to be encreas'd as much as the line of extent of the Medium which is to be overcome by the Agent in equal time exceeds the line of extent of the other Medium along which the resistant body is to be moved Wherfore it being proved that no line of extent can be overcome in an instant it follows that no defect of velocity which requires as great a superproportion in the cause can be overcome likewise in an instant And by the same reason by which we prove that a moveable cannot be drawn in an instant from a lower degree of velocity to a higher 't is with no less evidence concluded that no degree of velocity can be attain'd in an instant For divide that degree of velocity into two halfs and if the Agent had overcome the one half he could not overcome the other half in an instant much less therfore is he able to overcome the whole that is to reduce the moveable from quiet to the said degree of velocity in an instant Another reason may be because the movers themselvs such movers as we treat of here are Bodies likewise moved and consist of parts wherof not every one part but a competent number of them makes the moving body a fit Agent able to move the proposed body in a proposed degree of celerity Now this Agent meeting with resistance in the moveable and not being in the utmost extremity of density but condensable yet further because it is a body and every resistance be it never so small works something upon the mover though never so hard to condense it the parts of the mover that are to overcome this resistance in the moveable must to work that effect be condens'd and brought together as close as is needful by this resistance of the moveable to the mover and so the remote parts of the mover become nearer to the moveable which cannot be done but successively because it enclud's local motion And this application being likewise divisible and not all the parts flocking together in an instant to the place where they are to exercise their power it follows that whiles there are fewer moving parts knit together they must needs move less and more weakly then when more or all of them are assembled and appled to that work So that the motive virtue encreasing thus in proportion to the multiplying of the parts applied to cause the motion of necessity the effect which is obedience to be moved and quickness of motion in them oveable must do so too that is it must from nothing or from rest passe through al the degrees of celerityun till it arrive to that which all the parts together are able to cause As for example when with my hand I strike a ball till my hand touches it 't is in quiet but then it begins to move yet with such resistance that although it obey in some measure the stroke of my hand nevetiheless it presses the yeelding flesh of my palm backwards towards the upper and bony part of it That part then overtaking the other by the continu'd motion of my hand and both of them joyning together to force the ball away the impulse becomes stronger then at the first touching of it And the longer it presses upon it the more the parts of my hand condense and unite themselvs to excercise their force and the ball therfore must yeeld the more and consequent the motion of it 〈◊〉 quicker and quicker till my hand parts from it Which condensation of the parts of my hand encreasing successively by the parts joyning closer to one another the velocity of the balls motion which is an effect of it must also encrease proportionably therto And in like manner the motion of my hand and arm must grow quicker and quicker and pass all the degrees of velocity between rest and the utmost degree it attains unto For seeing they are the Spirits swelling the Nervs that cause the arms motion as we shall hereafter shew upon its resistance they flock from other parts of the body to evercome that resistance And since their journey thither requires time to perform it in and the nearest come first it must needs follow that as they grow more and more in number they must more powerfully overcome the resistance and consequently encrease the velocity of the motion in the same proportion as they flock thither till it attain that degree of velocity which is the utmost period that the power which the Agent hath to overcome the resistance of the medium can bring it self to Between which and rest or any other inferiour degree of velocity there may be design'd infinite intermediate degrees proportionable to the infinite divisibility of time and space in which the mover moves Which degrees arise out of the reciprocal yeilding of the medium And that is likewise divisible in the same infinite proportion Since then the power of all natural Agents is limited the mover be it never so powerful must be confined to observe these proportions and cannot pass over all these infinite designable degrees in an instant but must allot some time which hath a like infinity of designable parts to ballance this infinity of degrees of velocity and so consequently it requires time to attain to any determinate degree And therfore cannot recede immediately from rest to any degree of celerity but must necessarily pass through all the intermediate ones Thus 't is evident that all motion which hath a beginning must of necessity increase for some time And since the works of nature are
in proportion to their causes it follows that this encrease is in a determinate proportion Which Galileus to whom we owe the greatest part of what is known concerning motion teaches us how to find out and to discover what degree of celerity any movable that is moved by nature has in any determinate part of the space it moves in Having settled these conditions of motion we shall do well in the next place to enquire after the causes of it as well in the body moved as also in the mover that occasions the motion And because we have already shewed that local motion is nothing in substance but division we may determine that those causes which cōtribute to division or resist it are the causes which make or resist local motion It has also been said that Density has in it a power of dividing and that Rarity is the cause of being divided likewise we have said that fire by reason of its smal parts intow ch it may be cut which makes them sharp has also an eminence in dividing So that we have two qualities density and tenuity or sharpness which concur actively to division We have told you also how Galileus has demonstrated that a greater quantity of the same figure and density has a priviledge of descending faster than a lesser And that priviledge consists in this that the proportion of the superficies to the body it limits which proportion the greater it is the more it retards is less in a greater bulk than in a smaller We have therfore three conditions concurring to make the motion more efficacious namely the density the sharpness and the bulk of the movable and more then these three we cannot expect to find in a moved body For quantity hath but three determinations one by density rarity of which density is one of the three conditions another by its parts as by a foot a span c. and in this way we have found that the greater excells the lesser the third and last is by its figure and in this we find that subtile or edged quantities do prevail over blunt ones Seeing therfore that these three determinations be all that are in quantity there can be no more conditions in the body moved which of necessity is a finite quantity but the three named And as for the medium which is to be divided there is only rarity and density the one to help the other to hinder that require consideration on its side For neither figure nor littleness and greatness do make any variation in it And as for the Agent it is not as yet time before we have look'd further into the nature of motion to determine his qualities Now then let us reflect how these three conditions do all agree in this circumstance that they help nothing to division unless the body in which they are to be moved and press'd against the body that is to be divided so that we see no principle to perswade us that any body can move it self towards any determinate part or place of the universe of its own intrinsecal inclination For besides that the learned Author of the Dialogues de Mundo in his third Dialogue and the second Knot hath demonstrated that a body cannot move unless it be moved by some extrinsecal Agent we may easily frame to our selves a conceit how absurd it is to think that a body by a quality in it can work upon it self as if we should say that rarity which is but more quantity could work upon quantity or that figure which is but that the body reaches no further could work upon the body and in general that the manner of any thing can work upon that thing whose manner it is For Aristotle and St. Thomas and their Intelligent Commentators declaring the notion of Quality tell us that to be a Quality is nothing else but to be the determination or modification of the thing whose quality it is Besides the natural manner of operation is to work according to the capacity of the subject but when a body is in the midst of an uniform medium or space the subject is equally prepar'd on all sides to receive the action of that body Wherfore though we should allow it a force to move if it be a natural Agent and have no understanding it must work indifferently on all sides and by consequence cannot move on any side For if you say that the Agent in this case where the medium is uniform works rather upon one side than upon another it must be because this determination is within the Agent it self and not out of the circumstant dispositions which is the manner of working of those substances that work for an end of their own that is of understanding creatures and not of natural hodies Now he that would exactly determine what motion a body has or is apt to have determining by supposition the force of the Agent must calculate the proportions of all these three conditions of the movable and the quality of the medium which is a proceeding too particular for the intention of our discourse But to speak in common it will not be amiss to examine in what proportion motion doth increase since we have concluded that all motion proceeds from quiet by a continual encrease Galileus that miracle of our age and whose wit was able to discover whatever he had a mind to employ it about hath told us that natural motion encreases in the proportion of the odd numbers Which to express by example is thus suppose that in the going of the first yard it has one degree of velocity then in the going of the second yard it will have three degrees and in going of the third it will have five and so onwards still adding two to the degrees of the velocity for every one to the space Or to express it more plainly if in the first minute of time it goes one yard of space then in the next minute it will go three yards in the third it will go five in the fourth seaven and so forth But we must enlarge this proposition to all motions as we have done the former of the encrease it self in velocity because the reason of it is common to all motions Which is that all motion as may appear out of what we have formerly said proceeds from two causes namely the Agent or the force that moves and the disposition of the body moved as it is composed of the three qualities we lately explicated In which is to be noted that the Agent doth not move simply by its own virtue but applyes also the virtue of the body moved which it hath to divide the medium when it is put on As when we cut with a knife the effect proceeds from the knife press'd on by the hand or from the hand as applying and putting in action the edge and cutting power of the knife Now this in Physicks and Nature is clearly parallel to what in Geometry
and Arithmatick the Mathematicians call drawing one number or one side into another for as in Mathematicks to draw one number into another is to apply the number drawn to every part of the number into which it is drawn as if we draw three into seven we make twenty one by making every unity or part of the number seven to be three and the like is of lines in Geometry So in the present case to every part of the hands motion we add the whole virtue of the cutting faculty which is in the knife and to every part of the motion of the knife we add the whole pressing virtue of the hand Therfore the encrease of the effect proceeding from two causes so working must also be parallel to the encrease of the quantities arising out of the like drawing in Mathematicks But in those 't is evident that the encrease is according to the order of the odd numbers and therfore it must in our case be the like that is the encrease must be in the said proportion of odd numbers Now that in those the encrease proceeds so will be evident if you consider the encrease of an Equicrure Triangle which because it goes upon a certain proportion of length and breadth if you compare the encreases of the whole Triangle that gains on each side with the encreases of the perpendicular which gains only in length you will see that they will proceed in the foresaid proportion of odd numbers But we must not imagine that the velocity of motion will always encrease thus for as long as we can fancy any motion but when it is arrived to the utmost period that such a moveable with such causes is capable of then it keeps constantly the same pace and goes equally and uniformly at the same rate For since the density of the moveable the force of the Agent moving it which two cause the motion have a limited proportion to the resistance of the medium how yeilding soever it be it must needs follow that when the motion is arrived to that height which arises out of this proportion it cannot exceed it but must continue at that rate unless some other cause give yet a greater impulse to the movable For velocity consisting in this that the movable cuts through more of the medium in an equal time 't is evident that in the encrease of velocity the resistance of the medium which is overcome by it grows greater and greater and by little and little gains upon the force of the Agent so that the superproportion of the Agent grows still lesser and lesser as the velocity encreases and therfore at the length they must come to be ballanced and then the velocity can encrease no more And the reason of the encrease of it for a while at the beginning is because coming from rest it must pass through all the intermediate degrees of velocity before it can attain to the height of it which requires time to perform and therfore falls under the power of our sense to observe But because we see it do so for some time we must not therfore conclude the nature of such motion is still to encrease without any period or limit like those lines that perpetually grow nearer and yet can never meet for we see our reason examining the causes of this velocity assures us that in continuance of time and space it may come to its height which it cannot exceed And there would be the pitch at which distance weights being let fall would give the greatest strokes and make greatest impressions 'T is true that Galileus and Mersenius two exact experimenters do think they find this verity by their experiences But surely that is impossible to be done For the encrease of velocity being in a proportion ever diminishing must of necessity come to an insensible increase in proportion before it ends for the space which the movable goes through is still encreased and the time wherin it passes through that space remains still the same little one as was taken up in passing a less space immediately before such little differences of great spaces passed over in a little time come soon to be undiscernible by sense But reason which shews us that if velocity never ceased from encreasing it would in time arive to exceed any particular velocity and by consequence the proportion which the mover has to the medium because of the adding still a determinate part to its velocity concludes plainly that it is impossible motion should increase for ever without coming to a period Now the impression which falling weights make is of two kinds for the body into which impression is made either can yield backward or it cannot If it can yield backward then the impression made is a motion as we see a stroke with a Racket upon a Ball or with a Pail-mail beetle upon a Bowl makes it flie from it But if the strucken body cannot yield backwards then it makes it yield on the sides And this in divers matters for if the smitten body be drie and brittle 't is subject to break it and make the pieces flie round about but if it be a tough body it squeeses it into a larger form But because the effect in any of these ways is eminently greater than the force of the Agent seems to be 't is worth our labour to look into the causes of it To which end we may remember how we have already declared that the force of the velocity is equall to a reciprocall force of weight in the virtue movent wherefore the effect of a blow that a man gives with a hammer depends on the weight of the hammer on the velocity of the motion and on the hand in case the hand accompanies the blow But if the motion of the hand ceases before as when we throw a thing then only the velocity and the weight of the hammer remain to be consider'd However let us put the hand and weight in one sum which we may equalize by some other virtue or weight Then let us consider the way or space which a weight lying upon the thing is to go forwards to do the same effect in the same time as the percussion doth and what excess the line of the blow hath over the line of that way or space such an excess we must add of equal weight or force to the weight we had already taken And the weight composed of both will be a fit Agent to make the like impression This Problem was proposed to me by that worthy religious man Father Mersenius who is not content with advancing learning by his own industry and labours but besides is alwayes out of his generous affection to verity inciting others to contribute to the publick stock of it He proposed to me likewise this following question to wit why there is required a weight of water in double Geometrical proportion to make a pipe run twice as fast as it did or have twice as much
water run out in the same time To which I answer out of the same ground as before That because in running twice as fast there goes out double the water in every part of time and again every part of water goes a double space in the same part of time that is to say because double the celerity is drawn into double the water and double the water into doule the celerity therfore the present effect is to the former effect as the effect or quadrate of a double line drawn into into it self is to the effect or quadrate of half the said line drawn into it self And consequently the cause of the latter effect which is the weight then must be to the cause of the former effect that is to the former weight in the same proportion namely as the quadrate of a double line is to the quadrate of half that line And so you see the reason of what he by experience finds to be true Though I doubt not but when he shall set out the treatise which he has made on this subject the Reader will have better satisfaction In the mean while an experiment which Galileo delivers will confirm this doctrine He sayes that to make the same Pendant go twice as fast as it did or to make every undulation of it in half the time it did you must make the line at which it hangs double in Geometrical proportion to the line at which it hang'd before Whence it follows that the circle by which it goes is likewise in double Geometrical proportion And this being certain that celerity to celerity has the proportion of force which weight has to weight 't is evident that as in one case there must be weight in Geometrical proportion so in theother case where only celerity makes the variance the celerity must be in double Geometrical proportion according as Galileo finds it by experience But to return to our main intent there is to be further noted that If the subject strucken be of a proportionate cessibility it seems to dull and deaden the stroke wheras if the thing strucken be hard the stroke seems to lose no force but to work a greater effect Though indeed the truth be that in both cases the effects are equal but diverse according to the natures of the things that are strucken for no force that once is in nature can be lost but must have its adequate effect one way or other Let us then first suppose the body strucken to be a hard body of no exceeding bigness in which case if the stroke light perpendicularly upon it it will carry such a body before it But if the body be too great and have its parts so conjoyn'd that they are weaker then the stroke in this case the stroke drives one part before it and so breaks it from the rest But lastly if the parts of the strucken body be so easily cessible as without difficulty the stroke can divide them then it enters into such a body till it has spent its force So that now making up our account we see that an equal effect proceeds from an equal force in all the three cases though in themselves they be far different But we are apt to account that effect greater which is more considerable to us by the profit or damage it brings us And therefore we usually say that the blow which shakes a wall or beats it down and kills men with the stones it scatters abroad hath a greater effect then that which penetrates far into a mud wall and doth little harm for that innocuousness of the effect makes that although in it self it be as great as the other yet 't is little observ'd or consider'd This discourse draws on another which is to declare how motion ceases And to sum that up in short we say that When motion comes to rest it decreases and passes through all the degrees of celerity and tardity that are between rest and the height of that motion which so declines and that in the proportion of the odd numbers as we declared above it encreas'd The reason is clear because that which makes a motion cease is the resistance it findes which resistance is an action of a mover that moves something against the body moved or something equivalent to such an action wherefore it must follow the laws that are common to all motions of which kind those two are that we have expressed in this conclusion Now that resistance is a countermotion or equivalent to one is plain by this that any body which is pressed must needs press again on the body that presses it wherefore the cause that hinders such a body from yielding is a force moving that body against the body which presses it The particulars of all which we shall more at large declare where we speak of the action and reaction of particular bodies CHAP. X. Of Gravity and Levity and of Local Motion commonly term'd Natural IT is now time to consider that distinction of motions which is so famous in Aristotle to wit that some motions are natural others violent and to determine what may be signified by these terms For seeing we have said that no body hath a natural intrinsecal inclination to any place to which 't is able to move it self we must needs conclude that the motion of every body follows the percussion of extrinsecal Agents It seems therefore impossible that any body should have any motion natural to it self and if there be none natural there can be none violent and so this distinction will vanish to nothing But on the otherside Living creatures manifestly shew natural motions having natural instruments to perform certain motions wherefore such motions must of necessity be natural to them But these are not the motions we are to speak of for Aristotles division is common to all bodies or at the least to all those we converse with and particularly to those which are call'd heavy and light which two terms pass through all the bodies we have notice of Therefore proceeding on our grounds before lay'd to wit that no body can be moved of it self we may determine those motions to be natural to bodies which have constant causes or percutients to make them always in such bodies and those violent which are contrary to such natural motions Which being suppos'd we much search out the causes that so constantly make some bodies descend towards the center or the middle of the earth others to rise and go from the center by which the world is subject to those restless motions that keep all things in perpetual flux in this changing sphere of action and passion Let us then begin with considering what effects the Sun which is a constant and perpetual cause works on inferiour bodies by his being regularly sometimes present and sometimes absent Observe in a pot of water hanging over a fire how the heat makes some parts of the water ascend and others to supply the room
as positive gravity or levity but that their course upwards or downwards happens to them by the order of nature which by outward causes gives them an impulse one of these wayes without which they would rest quietly wherever they are as being of themselvs indifferent to any motion But because our words express our notions and they are fram'd according to what appears to us when we observe any body to descend constantly towards our earth we call it heavie and if it move contrarywise we call it light But we must take heed of considering such gravity and levity as if they were Entities that work such effects since upon examination it appears that these words are but short expressions of the effects themselves the causes whereof the vulgar of mankind who impose names to things do not consider but leave that work to Philosophers to examine whiles they onely observe what they see done and agree upon words to express that Which words neither will in all circumstances always agree to the same thing for as cork descends in aire and ascends in water so also will any other body descend if it lights among others more rare then it self and will ascend if it lights among others that are more dense then it And we term Bodies light and heavy only according to the course which we usually see them take Now proceeding further on and considering how there are various degrees of density or gravity it were irrational to conceive that all bodies should descend at the same rate and keep equal pace with one another in their journey downwards For as two knives whereof one hath a keener edge then the other being press'd with equal strength into like yielding matter the sharper will cut deeper then the other so if of two bodies one be more dense then the others that which is so will cut the air more powerfully and descend faster then the other for in this case density may be compared to the kniefs edge since in it consists the power of dividing as we have heretofore determin'd And therefore the pressing them downwards by the descending atomes being equal in both or peradventure greater in the more dense body as anon we shall have occasion to touch and there being no other cause to determine them that way the effect of division must be the greater where the divider is the more powerful Which the more dense body is and therefore cuts more strongly through the resistance of the air and consequently passes more swiftly that way 't is determin'd to move I do not mean that the velocities of their descent shall be in the same proportion to one another as their densities are for besides their density those other considerations which we have discours'd of above when we examin'd the causes of velocity in motion must likewise be ballanced And out of the comparisons of all them not out of the consideration of any one alone results the differences of their velocities nor that neither but in as much as concerns the consideration of the moveables for to make the calculation exact the Medium must likewise be considered as by and by we shall declare For since the motion depends of all them together though there should be difference between the moveables in regard of one only and that the rest were equal yet the proportion of the difference of their motions must not follow the proportion of their difference in that one regard because their difference consider'd single in that regard will have one proportion and with the addition of the other considerations though alike in both to their difference in this they will have another As for example reckon the density of one moveable to be double the density of another moveable so that in that regard it has two degrees of power to descend whereas the other has but one suppose then the other causes of thier descent to be alike in both and reckon them all three and then joyn these three to the one which is caused by the density in one of the moveables as likewise to the two which is caused by the density in the other moveable and you will find that thus altogether their difference of power to descend is no longer in a double proportion as it would be if nothing but their density were considered but is in the proportion of five to four But after we have consider'd all that concerns the moveables we are then to cast an eye upon the Medium they are to move in and we shall find the addition of that decreases the proportion of their difference exceedingly more according to the cessibility of the Medium Which if it be Air the great disproportion of its weight to the weight of those bodies which men use to take in making experiences of their descent in that yeelding Medium will cause their difference of velocity in descending to be hardly perceptible Even as the difference of a sharp or dull knife which is easily perceiv'd in cutting of flesh or bread is not to be distinguish'd in dividing of water or oyl And likewise in Weights a pound and a scruple will bear down a dram in no sensible proportion of velocity more then a pound alone would do and yet put a pound in that scale in stead of the dram and then the difference of the scruple will be very notable So then those bodies whose difference of descending in water is very sensible because of the greater proportion of weight in water to the bodies that descend in it will yield no sensible difference of velocity when they descend in air by reason of the great disproportion of weight between air and the bodies that descend in it The reason of this will clearly shew it self in abstracted proportions Thus Suppose air to have one degree of density and water to have 400 then let the moveable A. have 410 degrees of density and the moveable B. have 500. Now compare their motion to one another in the several mediums of air and water The exuperance of the density of A. to water is 10 degrees but the exuperance of B. to the same water is 100 degrees so that B. must have in water swifter then A in the proportion of 103 to ten that is of 10 to one Then let us compare the exuperance of the two moveables over air A is 409 times more dense then air but B is 499 times more dense then it by which account the motion of B. must be in that medium swifter then the motion of A in the proportion of 499 to 409 that is about 50 to 41 which to avoid fractions we may account as 10 to 8. But in water they exceed one another as 10 to one so that their difference of velocity must be scarce perceptible in air in respect of what it is in water Out of all which discourse I only infer in common that a greater velocity in motion will follow the greater density of the moveable without determining
here their proportions which I leave to them who make that examination their task for thus much serves my present turn wherein I take a survey of nature but in gross And my chief drift in this particular is only to open the way for the discovering how bodies that of themselves have no propension to any determinate place do nevertheless move constantly and perpetually one way the dense ones descending and the rare ones ascending not by any intrinsecal quality that works upon them but by the oeconomy of nature that hath set on foot due and plain causes to produce known effects Here we must crave patience of the great soul of Galileus whose admirable learning all posterity must reverence whiles we reprehend in him that which we cannot term lesse then absurd and yet he not only maintains it in several places but also professes Dial. Po. de motu pag. 81. to make it more clear then day His position is that more or less gravity contributes nothing at all to the faster or slower descending of a natural body but that all the effect it gives to a body is to make it descend or not descend in such a Medium Which is against the first and most known principal that is in bodies to wit that more doth more and less doth less for he allows that gravity causes a body to descend and yet will not allow that more gravity causes it to descend more I wonder he never mark'd how in a pair of scales a superproportion of the overweight in one ballance lifted up the other faster then a less proportion of overweight would do Or that more weight hang'd to a jack made the spit turn faster or to the lines of a Clock made it go faster and the like But his argument wherby he endeavours to prove his position is yet more wonderful for finding in pendants unequal in gravity that the lighter went in the same time almost as fast as the heavier he gathers from thence that the different weights have each of them the same celerity and that it is the opposition of the air which makes the lighter body not reach so far at each undulation as the heavier For reply whereto first we must ask him whether experience or reason taught him that the slower going of the lighter pendant proceeded only from the Medium and not from want of gravity And when he shall have answer'd as he needs must that experience doth not shew this then we must importune him for a good reason but I do not find that he brings any at all Again if he admits which he doth in express terms that a lighter body cannot resist the Medium so much as a heavier body can we must ask him whether it be not the weight that makes the heavier body resist more which when he has acknowledg'd that it is he has therein likewise acknowledg'd that whenever this happens in the descending of a body the more weight must make the heavier body descend faster But we cannot pass this matter without noting how himself makes good those arguments of Aristotle which he seems by no means to esteem of For since the gravity overcomes the resistance of the Medium in same some proportion it follows that the proportions between the gravity and the medium may be multiplied without end so as if he suppose that the gravity of a body makes it go at a certain rate in Imaginary Space which is his manner of putting the force of gravity then there may be given such a proportion of a heavy body to the medium as it shall go in such a medium at the same rate and nevertheless there will be an infinite difference betwixt the resistance of the medium compared to that body and the resistance of the Imaginary Space compared to that other body which he supposed to be moved in it at the same rate which no man will stick at confession to be very absurd Then turning the scales because the resistance of the medium somewhat hinders gravity and that with less resistance the heavy body moves faster it must follow that since there is no proportion betwixt the medium and imaginary space there must neither be any proportion betwixt the time in which a heavy body shall pass through a certain quantity of the medium and the time in which it shall pass through as much imaginary space wherefore it must pass over so much imaginary space in an instant Which is the argument that Aristotle is so much laugh'd at for pressing And in a word nothing is more evident then that for this effect which Galileo attributes to gravity 't is unreasonable to put a divisible quantity since the effect is indivisible And therfore as evident it is that in his doctrine such a quality as intrinsecal gravity is conceiv'd to be ought not to be put since every power should be fitted to the effect or end for which it is put Another argument of Galileo is as bad as this when he endeavours to prove that all bodies go of a like velocity because it happens that a lighter body in some case goes faster then a heavier body in another case as for example in two pendants whereof the lighter is in the beginning of its motion and the heavier towards the end of it or if the lighter hangs at a longer string and the heavier at a shorter we see that the lighter will go faster then the heavier But this concludes no more then if a man should prove a lighter goes faster then a heavier because a greater force can make it go faster for 't is manifest that in a violent motion the force which moves a body in the end of its course is weaker then that which moves it in the beginning and the like is of the two strings But here 't is not amiss to solve a Probleme he puts which belongs to our present subject He findes by experience that if two bodies descend at the same time from the same point and go to the same point the one by the inferiour quarter of the circle the other by the chord to that arch or by any other lines which are chords to parts of that arch he findes I say that the moveable goes faster by the arch then by any of the chords And the reason is evident if we consider that the nearer any motion comes to a perpendicular one downwards the greater velocity it must have and that in the arch of such a quadrant every particular part of it inclines to the perpendicular of the place where it is more then the part of the chord answerable to it doth CHAP. XI An Answer to Objections against the causes of natural motion avow'd in the former Chapter and a refutation of the contrary opinion BUt to return to the thrid of our Doctrine There may peradventure be objected against it that if the violence of a bodies descent towards the center did proceed only from the density of it which gives it
an aptitude the better to cut the medium and from the mltitude of little atomes descending that strike upon it and press it the way they go which is downwards then it would not import whether the inner part of that body were as solid as the outward parts for it cuts with only the outward and is smitten only upon the outward And yet experience shews us the contrary for a great bullet of lead that is solid and lead throughout descends faster then if three quarters of the Diameiter were hollow within and such a one falling upon any resisting substance works a greater effect then a hollow one And a ball of brass that hath but a thin outside of metal will swim upon the water when a massie one sinks presently Whereby it appears that it is rather some other quality belonging to the very bulk of the metal in it self and not these outward causes that occasion gravity But this difficulty is easily overcome if you consider how subtile those atomes are which descending downwards striking upon a body in their way cause its motion likewise downwards for you may remember how we have shew'd them to be the subtilest and the minutest divisions that Light the subtilest and sharpest divider in nature can make It is then easie to conceive that these extreme subtile bodies penetrate all others as light doth glass and run through them as sand through a small sieve or as water through a spunge so that they strike not only upon the Superficies but as well in every most interiour part of the whole body running quite through it all by the pores of it And then it must needs follow that the solider it is and the more parts it has within as well as without to be strucken upon the faster it go and the greater effect it must work in what falls upon whereas if three quarters of the Diameter of it within should be fill'd with nothing but air the atoms would fly without any considerable effect through all that space by reason of the rarity cessibility of it And that these atoms are thus subtile is manifest by several effects which we see in nature Divers Authors that write of Egypt assure us that though their houses be built of strong stone nevertheless a clod of earth laid in the inmost rooms and shut up from all appearing communication with air will encrease its weight so notably as therby they can judge the change of weather which will shortly ensue Which can proceed from no other cause but a multitde of little atoms of Saltpeter which floating in the air penetrate through the strongest wals and all the massie defences in their way and settle in the cold of earth as soon as they meet with it because it is of a temper fit to entertain and conserve embody them Delights have shewed us the way how to make the spirits or atoms of Snow and Saltpeter pass through a glass vessel which Alchimists hold to be the most impenetrable of all they can find to work with In our own bodies the aches which feeble parts feel before change of weather and the heaviness of our heads and shoulders if we remain in the open air presently after sunset abundantly testifie that even the grosser of these atoms which are the first that fall do vehemently penetrate our bodies so as sense will make us believe what reason peradventure could not But besides all this there is yet a more convincing reason why the descending atomes should move the whole density of a body even though it were so dense that they could not penetrate it and get into the bowels of it but must be content to strike barely upon the outside of it For nature has so order'd the matter that when dense parts stick close together and make the length composed of them to be very stiff one cannot be moved but that all the rest which are in that line must likewise be thereby moved so that if all the world were composed of atoms closse sticking together the least motion imaginable must drive on all that were in a straight line to the very end of the world This you see is evident in reason and experience confirms it when by a little knock given at the end of a long beam the shaking which makes sound reaches sensibly to the other end The blind man that governs his steps by feeling in defect of eyes receives advertisements of remote things through a staff which he holdeth in his hands peradventure more particularly then his eyes could have directed him And the like is of a deaf man that hears the sound of an Instrument by holding one end of a stick in his mouth whiles the other end rests upon the Instrument And some are of opinion and they not of the rank of vulgar Philosophers that if a staff were as long as to reach from the Sun to us it would have the same effect in a moment of time Although for my part I am hard to believe we could receive an advertisement so far unless the staff were of such a thickness as being proportionable to the length might keep it from facile bending for if it should be very plyant it would do us no service as we experience in a thrid which reaching from our hand to the ground if it knock against any thing makes no sensible impression in our hand So that in fine reason sense and authority all of them shew us that the less the atomes should penetrate into a moving body by reason of the extreme density of it the more efficaciously they would work and the greater celerity they would cause in its motion And hence we may give the fullest solution to the objection above Which was to this effect that seeing division is made only by the superficies or exteriour part of the dense body and the virtue whereby a dense body works is onely its resistance to division which makes it apt to divide it would follow that a hollow bowl of brass or iron should be as heavy as a solid one For we may answer that seeing the atoms must strike through the body and a cessible body doth not receive their strokes so firmly as a stiffe one nor can convey them so far if to a stiff superficies there succeed a yielding inside the strokes must of necessity lose much of their force and consequently cannot move a body full of air with so much celerity or with so much efficacy as they may a solid one But then you may peradventure say that if these strokes of the descending atomes upon a dense body were the cause of its motion downwards we must allow the atomes to move faster then the dense body that so they may still overtake it and drive it along and enter into it whereas if they should move slower then it none of them could come in their turn to give it a stroke but it would be past them and out of their reach before they
notable degree as for example to water makes then a great difference of a heavy bodies gravitation in it and accordingly we see a great difference between heavy bodies descending in water and in air though between two kinds of air none is to be observ'd their difference is so smal in respect of the density of the body that descends in them And therfore since an assured and certain difference in circumstances makes no sensible inequality in the affect we cannot expect any from such circumstances as we may reasonably doubt whether there be any inequality among them or no. Besides that if in any of the proposed cases a heavy body should gravitate more and be heavier one time than another yet by weighing it we could not discern it since the counterpoise which is to determine its weight must likewise be in the same proportion heavier then it was And besides weighing no other means remains to discover its greater graviation but to compare it to Time in its descent and I believe that in all such distances as we can try it in its inequalities will be no whit less difficult to be observ'd that way then any other Lastly to bend our discourse particularly to that instance of the objection where it is conceiv'd that if gravity or descending downwards of bodies proceeded from atoms striking on them as they move downwards it would follow that a stone or other dense body lying under shelter of a thick hard and impenetrable adamantine rock would have no impulse downwards and consequently would not weigh there We may note that no body whatever compacted by physical causes and agents can be so dense and imporous but that such atoms as these we speak of must be in them and in every part of them and every where pass through and through them as water doth through a sieve or through a spunge and this universal maxime must extend as far as the Sun or any other heat communicating with the Sun reaches and is found The reason whereof is because these atoms are no other thing but such extreme little bodies as are resolved by heat out of the main stock of those massie bodies upon which the Sun and heat do work Now then it being certain out of what we have heretofore said that all mixt bodies have their temper and consistence and generation from the mingling of fire with the rest of the Elements that compose them and from the concoction or digestion which fire makes in those bodies 't is evident that no mixt body whatever nor any sensible part of a mixt body can be void of pores capable of such atoms or be without such atoms passing through those pores which atoms by mediation of the air that likewise hath its share in such pores must have communication with the rest of the great sea of air and with the motions that pass in it And consequently in all and every sensible part of any such extreme dense and pretended inpenetrable body to the notice wherof we can arrive this percussion of atoms must be found and they will have no difficulty in running through nor by means of it in striking any other body lying under the shelter of it and thus both in from that hard body there must be stil an uninterrupted continuation of gravity or of descending towards the centre To which we may adde that the stone or dense body cannot lie so close to the rock that covers it but that some air must be between for if nothing were between they would be united and become one continued body and in that air which is a Creek of the great Ocean of air spread over the world that is every where bestrew'd with moving atoms and which is continually fed like a running stream with new air that drives on the air it overtakes no doubt but there are descending atoms as well as in all the rest of its main body and these descending atoms meeting with the stone must needs give some stroke upon it and that stroke be it never so little cannot chuse but work some effect in making the stone remove a little that way they go and that motion wherby the space is inlarg'd between the stone and the shelt'ring rock must draw in a greater quantity of air and atoms to strike upon it And thus by little and little the stone passes through all the degrees of tardity by which a descending body parts from rest which is by so much the more speedily done by how much the body is more eminent in density But this difference of time in regard of the atoms strokes only and abstracting from the bodies density will be insensible to us seeing as we have said no more is required of them but to give a determination downwards And out of this we clearly see the reason why the same atoms striking upon one body lying on the water make it sink and upon another they do not As for example if you lay upon the superficies of some water a piece of iron and a piece of cork of equal bigness and of the same figure the iron will be beaten down to the bottom and the cork will float at the top The reason wherof is the different proportions of the comparison of their densities with the density of water for as we have said the efficacy and force of descending is to be measured by that So then the strokes of the atoms being more efficatious upon water then upon cork because the density of water is greater then the density of cork considering the abundance of air that is harbor'd in the large pores of it it followes that the atoms will make the water go down more forcibly then they will cork But the density of iron exceeding the density of water the same strokes will make the iron descend faster then the water and consequently the iron must sink in the water and the cork will swim upon it And this same is the cause why if a piece of cork be held by force at the bottom of the water it will rise up to the top as soon as the violence is taken away that kept it down for the atoms strokes having more force on the water then on the cork they make the water sink and slide under it first a little thin plate of water and then another a little thicker and so by degrees more and more till it hath lifted the cork quite up to the top Fifthly it may be objected that these atoms do not descend always perpendicularly but somtimes slopingly and in that case if their strokes be the cause of dense bodies moving they should move sloping and not downward Now that these atoms descend somtimes slopingly is evident as when for example they meet with a stream of water or with a strong wind or even with any other little motion of the air such as carries feathers up and down hither and thither which must needs waft the atoms in some measure along
with them their way Seeing then that such a gentle motion of the air is able to put a feather out of its way notwithstanding the percussions of the atoms upon it why shall it not likewise put a piece of iron out of its way downwards since the iron hath nothing from the atoms but a determination to its way But much more why should not a strong wind or a currant of water do it since the atoms themselv's that give the iron its determination must needs be hurried along with them To this we answer that we must consider how any wind or water which runs in that sort is it self originally full of such atoms which continually and every where press into and cut through it in pursuing their constant perpetual course of descending in such sort as we shewed in their running through any hard rock or other densest body And these atoms make the wind or water primarily tend downwards though other accidental causes impel them secundarily to a sloping motion And still their primary natural motion will be in truth strongest though their not having scope to obey that but having enough to obey the violent motion makes this become the more observeable Which appears evidently out of this that if there be a hole in the bottome of the pipe that conveys water slopingly be the pipe never so long and consequently the sloping motion never so forcible yet the water will run out at that hole to obey its more powerful impulse to the centrewards rather then continue the violent motion in which it had arrived to a great degree of celerity Which being so 't is easie to conceive that the atoms in the wind or water which move perpendicularly downwards will still continue the irons motion downwards notwithstanding the Mediums sloping motion since the prevailing force determines both the iron and the Medium downward and the iron has a superproportion of density to cut its way according as the prevalent motion determines it But if the descending atoms be in part carried along down the stream by the current of wind or water yet still the current brings with it new atoms into the place of those that are carried away and these atoms in every point or place wherever they are of themselvs tend perpendicularly downwards though they are forced from the compleat effect of their tendance by the violence of the current so that in this case they are moved by a declining motion compounded of their own natural motion and the force one with which the stream carries them Now then if a dense body fall into such a current where these different motions give their several impulses it will be carried in such sort as we say of the atoms but in another proportion not in a perpendicular but in a mixt declining line compounded of the several impulses which the atoms and current give it in which also 't is to be remembred how the current gives an impulse downwards as well as sloping and peradventure the strongest downwards and the declination will be more or less according as the violent impulse prevails more or less against the natural motion But this is not all that is to be consider'd in estimating the declination of a dense bodies motion when it is sinking in a current of wind or water You must remember that the dense body it self has a particular virtue of its own namely its density by which it receivs and prosecutes more fully its determination downwards and therfore the force of that body in cutting its way through the Medium is also to be considered in this case as well as above calculating its declining from the perpendicular and out of all these causes will result a middle declination compounded of the motion of the water or wind both ways and of its own motion by the perpendicular line And since of these three causes of a dense bodies motion it s own virtue in prosecuting by its density the determination it requires is the most efficacious by much after it has once receiv'd a determination from without its declination will be but little if it be very dense and heavy But if it recede much from density as so have some near proportion to the density of the Medium the declination will be great And in a word according as the body is heavier or lighter the declination will be more or less in the some current though not exactly according to the proportion of the diminishing of its density as long as there is a superproportion of its density to the Medium since such a superproportion as we have declared heretofore makes the Mediums operation upon the dense body scarce considerable And hence you see why a stone or piece of iron is not carried out of its way as well as a feather because the stones motion downwards is greater and stronger then the motion of a feather downwards And by consequence the force that can turn a feather from its course downwards is not able to deturn a stone And if it be repli'd that it may be so order'd that the stone shall have no motion before it be in the stream of a river and notwithstanding it will still move downwards we may answer that considering the little declivity of the bed of such a stream the strongest motion of the parts of the stream must necessiariy be downwards and consequently they will beat the stone downwards And if they do not the like to a feather or other light body 't is because other parts of the stream get under the light body and beat it upwards which they have not power enough to do to the stone Sixthly it may be objected that if Elements do not weigh in their own Spheres then their gravity and descending must proceed from some other cause and not from this percussion of the atoms we attribute to it which percussion we have determin'd goes through all bodies whatever and beats upon every sensible part of them But that Elements weigh not in their own Spheres appears out of the experience of a Syphon for though one leg of a Syphon be sunk never so much deeper into the body of the water then the other leg reaches below the superficies of the water nevertheless if once the outward leg become full of water it will draw it out of the other longer leg Which it should not do if the parts of water that are comprised within their whole bulk did weigh since the bulk of water is much greater in the sunk leg then in the other and therfore these should rather draw back the other water into the Cistern then be themselves drawn out of it into the air To this we answer that 't is evident the Elements do weigh in their own Spheres at least as far as we can reach to their Spheres for we see that a ball once stuff'd hard with air is heavier then an empty one Again more water would not be heavier then less if the inward
parts of it did not weigh and if a hole were dig'd in the bottome of the Sea the water would not run into and fill it if it did not gravitate over it Lastly there are those who undertake to distinguish in a deep water the divers weights which several parts of it have as they grow still heavier and heavier towards the bottom and they are so cunning in this art that they profess to make instruments which by their equality of weight to a determinate part of the water shall stand just in that part and neither rise or fall higher or lower but if it be put lower it shall ascend to its exact equally weighing Orbe of the water and if it be put higher it shall descend till it comes to rest precisely in that place Whence 't is evident that parts of water do weigh within the bulk of their main body and of the like we have no reason to doubt in the other two weighty Elements As for the opposition of the Syphon we refer that point to where we shall have occasion to declare the nature of that engine on set purpose And there we shall shew that it could not succeed in its operation unless the parts of water did gravitate in their main bulk into which one leg of the Syphon is sunk Lastly it may be objected that if there were such a course of atoms as we say and their strokes were the cause of so notable an effect as the gravity of heavy bodies we should feel it palpably in our own bodies which experience shews us we do not To this we answer first that there is no necessity we should feel this course of atoms since by their subtilty they penetrate all bodies and consequently do not give such strokes as are sensible Secondly if we consider that dusts and straws and feathers light upon us without causing any sense in us much more we may conceive that atoms which are infinitely more subtile and light cannot cause in us any feeling of them Thirdly we see that what is continual with us and mingled in all things doth not make us take any especial notice of it and this is the cause of the smiting of atoms Nevertheless peradventure we feel them in truth as often as we feel hot and cold weather and in all Catars or other such changes which as it were sink into our body without our perceiving any sensible cause of them for no question these atomes are the immediate causes of all good and bad qualities in the air Lastly when we consider that we cannot long together hold out our arm at length or our foot from the ground and reflect upon such like impotencies of our resisting the gravity of our own body we cannot doubt but that in these cases we feel the effect of these atomes working upon those parts though we cannot by our sense discern immediately that these are the causes of it But now it is time to draw our Reader out of a difficulty which may peradventure have perplext him in the greatest part of what he hath hitherto gone over In our investigation of the Elements we took for a principle thereto that gravity is sometimes more sometimes less then the density of the body in which it is but in our explication of rarity and density and again in our explication of gravity we seem to put that gravity and density is all one This thorn I apprehend may in all this distance have put some to pain but it was impossible for me to remedy it because I had not yet deliver'd the manner of gravitation Here then I will do my best to asswage their grief by reconciling these appearing repugnancies We are therefore to consider that density in it self signifies a difficulty to have the parts of its subject separated one from another and that gravity likewise in it self signifies a quality by which a heavy body descends towards the center or which is consequent thereto a force to make another body descend Now this power we have shew'd belong to density so far forth as a dense body being strucken by another doth not yield by suffering its parts to be divided but with its whole bulk strikes the next before it and divides it if it be more divisible then it self is So that you see Density has the name of Density in consideration of a passive quality or rather of an impassibility which it hath and the same density is call'd Gravity in respect of an active quality it has which follows this impassibility And both of them are estimated by the different respects which the same body or subject in which they are has to different bodies that are the terms whereto it is compared for the active quality or Gravity of a dense body is esteem'd by its respect to the body it strikes upon whereas its Density includes a respect singly to the body that strikes it Now 't is no wonder that this change of comparison works a disparity in the denominations and that thereby the same body may be conceiv'd to be more or less impartible then it is active or heavy A for example let us of a dense Element take any one least part which must of necessity be in its own nature and kind absolutely impartible and yet 't is evident that the gravity of this part must be exceeding little by reason of the littleness of its quantity so that thus you see an extremity of the effect of density joyn'd together in one body by the accident of its littleness with a contrary extremity of the effect of gravity or rather with the want of it each of them within the limits of the same species In like manner it happens that the same body in one circumstance is more weighty in another or rather in the contrary is more partible So water in a Pail because 't is thereby â—hinder'd from spreading abroad has the effect of gravity predominating in it but if it be pour'd out it has the effect of partibility more And thus it happens that meerly by the gradation of rarity and density one dense body may be apt out of the general course of natural causes to be more divisible then to be a divider though according to the nature of the degrees consider'd absolutely in themselves what is more powerful to divide is also more resistent and harder to be divided And this arrives in that degree which makes water for the falling and beating of the atomes upon water hath the power both to divide and make it descend but so that by making it descend it divideth it And therefore we say it has more gravity then density though it be the very density of it which is the cause that makes it partible by the working of one part upon another for if the atomes did not find the body so dense as it is they could not by their beating upon one part make another be divided So that a dense body to be more heavy then
continue some time before it can be settled and it being determin'd by the motion of the arrow that way that it slides it follows that all this commotion and undulation of the air serves to continue the arrow in its flight And thus faster then any part behind can be setled new ones before are stir'd till the resistance of the medium grows stronger then the impulse of the movers Besides this the arrow pressing on the air before it with a greater velocity then the air which is a liquid rare body can admit to move all of a piece without breaking it must of necessity happen that the parts of the air immediately before the arrow be driven upon others further off before these can be moved to give place unto them so that in some places the air becomes condens'd and consequently in others rarified Which also the wind we make in walking which will shake a paper pin'd loosly at the wall of a chamber towards which we walk and the cooling air caus'd by faning when we are hot do evidently confirm So that it cannot be doubted but condensation and rarefaction of the air must necessarily follow the motion of any solid body which being admitted 't is evident that a greater disorder and for some remarkable time must necessarily be in the air since it cannot brook to continue in more rarity or density then is natural to it Nor can weighty and light parts agree to rest in an equal height or lowness which the violence of the arrows motion forces them to for the present Therefore it cannot be deni'd but that though the arrow slide away there still remains behind it by this condensation and confusion of parts in the air motion enough to give impulse to the arrow so as to make it continue its motion after the bowstring has left it But here will arise a difficulty which is how this clapping in and undulation of the air should have strength and efficacy enough to cause the continuance of so smart a motion as is an arrow shot from a bow To this I need no other argument for an answer then to produce Galileo's testimony how great a body one single mans breath alone can in due circumstances give a rapid motion to and withal let us consider how the arrow and the air about it are already in a certain degree of velocity that is to say the obstacle that would hinder it from moving that way namely the resistance of the air is taken away and the causes that are to produce it namely the determining of the airs and atomes motion that way are heightned And then we may safely conclude that the arrow which of it self is indifferent to be moved upwards or downwards or forwards must needs obey that motion which is caused in it by the atomes and the air 's pressing upon it either according to the impulse of the string or when the string begins to flag according to the beating that follows the general constitution of nature or in a mixt manner according to the proportions that these two hold to one another Which proportions Galileus in his 4 Dialogue of Motion has attempted to explicate very ingeniously but having miss'd in one of his suppositions to wit that forced motion upon an Horizontal line is throughout uniform his great labours therein have taken little effect towards the advancing the knowledge of nature as he pretended for his conclusions succeed not in experience as Mersenius assures us after very exact trials nor can they in their reasons be fitted to nature So that to conclude this point I find no difficulty in allowing this motion of the air strength enough to force the moveable onwards for sometime after the first mover is sever'd from it and long after we see no motions of this nature endure so that we need seek no further cause for the continuance of it but may rest satisfied upon the whole matter that since the causes and circumstances our reason suggests to us are after mature and particular examination proportionable to the effects we see the doctrine we deliver must be sound and true For the establishing wherof we need not considering what we have already said spend much time in solving Galileo's arguments against it seeing out of what we have set down the answers to them appear plain enough For first we have assign'd causes how the air may continue its motion long enough to give as much impression as is needful to the arrow to make it go on as it does Which motion is not requisite to be near so great in the air behind the arrow that drives it on as what the arrow causes in the air before it for by reason of its density it must needs make a greater impression in the air it cuts then the air causes its motion would do of it self without the mediation of the arrow As when the force of a hand gives motion to a knife to cut a loaf of bread the knife by reason of the density and figure it has makes a greater impression in the loaf then the hand alone would do And this is the same that we declared in the natural motion of a heavy thing downwards to which we assigned two causes namely the beating of the atoms in the air falling down in their natural course to determine it the way it is to go and the density of the body that cutting more powerfully then those atoms can do gives together with their help a greater velocity to the moveable then the atoms of themselves can give Nor imports it that our resolution it aginst the general nature of rare and dense bodies in regard of conserving motion as Galileo objects For the reason why dense bodies conserve motion longer then rare bodies is because in regard of their dividing virtue they get in equal time a greater velocity Wherfore seeing velocity is equal to gravity it follows that resistance works not so much upon them as upon rare bodies and therfore cannot make them cease from motion so easily as it does rare bodies This is the general reason for the conservation of motion in dense bodies But because in our case there is a continual cause which conserves motion in the air the air may continue its motion longer than of it self it would do not in the same part of air which Galileus as it seems aim'd at but in divers parts in which the moveable successively is Which being concluded let us see how the forced motion comes to decrease and be ended To which purpose we may observe that the impression which the arrow receives from the air that drives it forwards being weaker than that which it receiv'd at first from the string by reason that the air is not so dense and therfore cannot strike so great a blow the arrow does not in this second measure of time wherein we consider the impulse given by the air only cut so strongly the air before it nor press so
violently upon it as in the first measure when the string parting from it did beat it forwards for till then the velocity encreases in the arrow as it does in the string that carries it along which proceeds from rest at the fingers loose from it to its highest degree of velocity which is when it arrives to the utmost extent of its jerk where it quits the arrow And therfore the air now doth not so swiftly nor so much of it rebound back from before and clap it self behind the arrow to fill the space that else would be left void by the arrows moving forward and consequently the blow it gives in the third measure to drive the arrow on cannot be so great as the blow was immediately after the strings parting from it which was in the second measure of time and therefore the arrow must needs move slower in the third measure than it did in the second as formerly it moved slower in the second which was the airs first stroke than it did in the first when the string drove it forwards And thus successively in every moment of time as the causes grow weaker weaker by the encrease of resistance in the air before and by the decrease of force in the subsequent air so the motion must be slower and slower till it come to pure cessation As for Galileu's second argument that the air has little power over heavy things and therfore he will not allow it to be the cause of continuing forced motions in dense bodies I wish he could as well have made experience what velocity of motion a mans breath might produce in an heavy bullet lying upon an even hard and slippery plain for a table would be too short as he did how admirable great a one it produced in pendants hanging in the air and I doubt not but he would have granted it as powerful in causing horizontal motions as he found it in the undulations of his pendants Which nevertheless sufficiently convince how great a power air has over heay bodies As likewise the experience of wind-guns assures us that air duly applyed is able to give greater motion to heavy bodies than to light ones For how can a straw or feather be imagin'd possibly to fly with half the violence as a bullet of lead doth out of one of those Engines And when a man sucks a bullet upwards in a perfectly bored barrel of a Gun which the bullet fits exactly as we have mention'd before with what a violence doth it follow the breath and ascend to the mouth of the barrel I remember to have seen a man that was uncautious and sucked strongly that had his foreteeth beaten out by the blow of the bullet ascending This experiment if well look'd into may peradventure make good a great part of this Doctrine we now deliver For the air pressing in behind the bullet at the touch-hole gives it its impulse upwards to which the density of the bullet being added you have the cause of its swiftness and violence for a bullet of wood or cork would not ascend so fast and so strongly and the sucking away of the air before it takes away that resistance which otherwise it would encounter with by the air lying in its way and its following the breath with so great ease shews as we touch'd before that of it self 't is indifferent to any motion when nothing presses upon it to determine it a certain way Now to Galileo's last argument that an arrow should fly faster broad-ways than long-ways if the air were cause of its motion there needs no more to be said but that the resistance of the air before hinders it as much as the impulse of the air behind helps it on So that nothing is gain'd in that regard but much is lost in respect of the figure which makes the arrow unapt to cut the air so well when it flyes broad-ways as when 't is shot long-ways and therfore the air being weakly cut so much of it cannot clap in behind the arrow and drive it on against the resistance before which is much greater Thus far with due respect and with acknowledging remembrance of the many admirable mysteries of nature which that great man hath taught the world we have taken liberty to dipute against him because this difficulty seems to have driven him against his Genius to believe that in such motions there must be allow'd a quality imprinted into the moved body to cause them which our whole scope both in this and all other occasions where like qualities are urged is to prove superfluous and ill grounded in nature and to be but meer terms to confound and leave in the dark whoever is forced to fly to them CHAP. XIII Of three sorts of violent motion Reflection Undulation and Refraction THe motion we have last spoken of because 't is ordinarily either in part or wholy contrary to gravity which is accounted the natural motion of most bodies uses to be call'd violent or forced And thus you have deliver'd you the natures and causes both of Natural and of Forced Motion yet it remains that we advertise you of some particular kinds of this forced motion which seem to be different from it but indeed are not As first the motion of Reflection which if we but consider how forced motion is made we shall find it is nothing else but a forced motion whose line whereon 't is made is as it were snapp'd in two by the encounter of a hard body For even as we see in a spout of water strongly shot against a wall the water following drives the precedent parts first to the wall and afterwards coming themselves to the wall forces them again another way from the wall so the latter parts of the torrent of air which is caused by the force that occasion'd the forced motion drives the former parts first upon the resistant body and afterwards again from it But this is more eminent in light than in any other body because light doth less rissent gravity and so observes the pure course of the stroke better than any other body from which others for the most part decline some way by reason of their weight Now the particular law of reflection is that the line incident the line of reflection must make equal angles with that line of the resistent superficies wch is in the same superficies with themselvs The demonstration wherof that great wit Renatus des Cartes hath excellently set down in his book of Dioptricks by the example of a ball strucken by a Racket against the earth or any resisting body the substance wherof is as follows The motion which we call Undulation needs no further explication for 't is manifest that since a Pendent when 't is removed from its perpendicular will restore it self therto by the natural force of gravity and that in so doing it gains a velocity and therefore cannot cease on a suddain it must needs be
same point of incidence in a shorter line and a greater angle than another does In both these wayes 't is apparent that a body composed of greater parts and greater pores exceeds bodies of the opposite kind for by reason that in the first kind more light may beat against one part a body in which that happens will wake an appearance from a further part of its superficies wheras in a body of the other sort the light that beats against one of the little parts of it will be so little as 't will presently vanish Again because in the first the part at the incidence is greater the surface from which the reflection is made inwards has more of a plain and straight superficies and consequently reflects at a greater angle than that whose superficies hath more of inclining But we must not pass from this question without looking a little into the nature of those bodies in which refraction is made for if they as well as the immediate causes of refraction likewise favour us it will not a little advance the certainty of our determination To this purpose we may call to mind how experience shews us that great refractions are made in smoke and mists and glasses and thick-bodied waters and Monsir des Cartes adds certain Oyls and Spirits or strong Waters Now most of these we see are composed of little consistent bodies swimming in another liquid body As is plain in smoke and mists for the little bubbles which rise in the water before they get out of it and that are smoke when they get into the air assure us that smoke is nothing else but a company of little round bodies swimming in the air and the round consistence of water upon herbs leavs twigs in a rind or dew gives us also to understand that a Mist is likewise a company of little round bodies that sometimes stand sometimes float in the air as the wind drives them Our very eyes bear witness to us that the thicker sort of waters are full of little bodies which is the cause of their not being clear As for Glass the blowing of it convinces that the little darts of fire which pierce it every way do naturally in the melting of it convert it into little round hollow bodies which in their cooling must settle into parts of the like figure Then for Chrystal and other transparent stones which are found in cold places it cannot be otherwise but that the nature of cold piercing into the main body and contracting every little part in it self this contraction must needs leave vacant pores between part and part And that such transparent stones as are made by heat have the like effect and property may be judg'd out of what we see in Bricks and Tiles which are left full of holes by the operation of the fire And I have seen in bones that have lain a long time in the Sun a multitude of sensible little pores close to one another as if they had been formerly stack all over with subtile sharp needles as close as they could be thrust in by one another The Chymical Oyles and Spirits which Monsir des Cartes speaks of are likely to be of the same composition since such use to be extracted by violent fires for a violent fire is made by the conjunction of many rayes together and that must needs cause great pores in the body it works on and the sticking nature of these spirits is capable of conserving them Out of all these observations it follows that the bodies in which greatest refractions happen are compounded as we have said of great parts and great pores and therfore by only taking light to be such a body as we have described it where we treated of its nature 't is evident the effect we have exprest must necessarily follow by way of reflection and refraction is nothing else but a certain kind of reflection Which last assertion is likewise convinced out of this that the same effects proceed from reflection as from refraction for by reflection a thing may be seen greater than it is in a different place from the true one where it is colours may be made by reflection as also gloating light and fire likewise and peradventure all other effects which are caused by refraction may as well as these be perform'd by reflection And therfore 't is evident they must be of the same nature since children are the resemblances of their parents CHAP. XIV Of the composition qualities and generation of mixed bodies HAving now declar'd the vertues by which Fire and Earth work upon one another and upon the rest of the Elements which is by Light and the motions we have discours'd of Our task shall be in this Chapter first to observe what will result out of such action of theirs and next to search into the ways and manner of compassing and performing it Which latter we shall the more easily attain to when we first know the end that their operation levels at In this pursuit we shall find that the effect of the Elements combinations by means of the motions that happen among them is a long pedegree of compounded qualities and bodies wherein the first combinations like marriages are the breeders of the next more-composed substances and they again are the parents of others in greater variety and so are multiplied without end for the further this work proceeds the more subjects it makes for new business of the like kind To descend in particular to all these is impossible And to look further then the general heads of them were superfluous and troublesome in this discourse wherin I aim only at shewing what sorts of things in common may be done by Bodies that if hereafter we meet with things of another nature and strain we may be sure they are not the off-spring of bodies and quantity which is the main scope of what I have design'd here And to do this with confidence certainty requires of necessity this leisurely and orderly proceeding we have hitherto used and shall continue to the end For walking thus softly we have always one foot upon the ground so as the other may be sure of firm footing before it settle Wheras they that for more hast will leap over rugged passages and broken ground when both their feet are in the air cannot help themselvs but must light as chance throws them To this purpose then we may consider that the qualities of bodies in common are of three sorts For they are belonging either to the Constitution of a compounded body or else to the Operation of it and the Operation of a body is of two kinds one upon Other Bodies the other upon Sense The last of these three sorts of qualities shall be handled in a peculiar Chapter by themselvs Those of the second sort wherby they work upon Other bodies have been partly declar'd in the former chapters and will be further discours'd of in the rest of this first
soft and liquid bodies easily joyn and incorporate into one continued body but hard and dry bodies so difficultly as by experience we find to be true Water with water or wine either with other wine or with water so unites that 't is very hard to part them but sand or stones cannot be made to stick together without very great force and industry The reasons whereof must necessarily depend of what we have said above To wit that two bodies cannot touch one another without becoming one and that if two bodies of one degree of density do touch they must stick together according to the force of that degree of density Out of which two is manifestly infer'd that if two hard things should come to touch they must needs be more difficultly separated then two liquid things And consequently they cannot come to touch without as much difficulty as that wherby they are made one But to deduce this more particularly let us consider that all the little surfaces by which one hard body may be conceiv'd to touch another as for example when a stone lies upon a stone must of necessity be either plain or concave or convex Now if a plain superficies should be supposed to touch another plain one coming perpendicularly to it it must of necessity be granted to touch it as soon in the middle as on the sides Wherfore if there were any air as of necessity there must be betwixt the two surfaces before they touch'd it will follow that the air which was in the midle must have fled quite out from between the two surfaces as soon as any part of the surfaces touch that is as soon as the air which was between the utmost edges of the surfaces did fly out and by consequence it must have moved in an instant But if a plain surface be said to touch a convex surface it touches it only by a line as Mathematicians demonstrate or a point But to touch by a line or a point is in truth not to touch by the form or motion of Quantity which requires divisibility in all that belongs to it and by consequence among bodies it is not-to-touch and so one such surface doth not touch the other Now for a plain surface to touch a concave every man sees is impossible Likewise for two convex surfaces to touch one another they must be allow'd to touch either in a line or in a point which we have shew'd not to be a physical touching And if a convex surface should be said to touch a concave they must touch all at once as we said of plain surfaces and therfore the same impossibility will arise therein So that 't is evident no two surfaces moving perpendicularly towards one another can come to touch one another if neither of them yields and changes its hew Now then if it be supposed they come slidingly one over another in the same line wherby first the very tips of the edges come to touch one another and still as you shove the uppermost on forwards and it slides over more of the nether surface it gains to touch more of it I say that neither in this case do they touch immediately one another For as soon as the two first parts should meet if they did touch and there were no air between them they must presently become one quantity or body as we have declared and must stick firmly together according to their degree of density and consequenly could not be moved on without still breaking asunder at every impulse as much of the massie body as were already made one by their touching And if you should say they did not become one and yet allow them to touch immediately one another without having any air or fluid body between them then if you suppose them to move onwards upon these terms they would be changed locally without any intrinsecal change which in the book De Mundo as we have formerly alledg'd is demonstrated impossible There remains only a third way for two hard surfaces to come together which is that first they should rest sloping one upon another and make an angle where they meet as two lines that cut one another doe in the point of their intersection and so contain as it were a wedge of air between them which wedge they should lessen by little and little through their moving towards one another at their most distant edges whiles the touching edges are like immoveable centers that the others turn upon till at length they shut out all the air and close together like the two legs of a compass But neither is it possible that this way they should touch For after their first touch by one line which neither is in effect a touching as we have shewed no other parts of them can touch though still they approach nearer and nearer till their whole surfaces entirely touch at once and therefore the air must in this case leap out in an instant a greater space then if the surfaces came perpendicularly to one another for here it must flie from one extremity to the other whereas in the former case it was to go but from the middle to each side And thus 't is evident that no two bodies can arrive to touch one another unless one of them at the least have a superficies plyable to the superficies of the other that is unless one of them be soft which is to be liquid in some degree Seeing then that by touching bodies become one and liquidity is the cause and means whereby bodies arrive to touch we may boldly conclude that two liquid bodies most easily and readily become one and next to two such a liquid and a hard body are soonest united but two hard ones most difficultly To proceed then with our reflections upon the composition of Bodies and upon what results out of the joyning and mixture of their first differences Rarity and Density we see how if a liquid substance happens to touch a dry body it sticks easily thereto Then consider there may be so small a quantity of such a liquid body as it may be almost impossible for any natural agent to divide it further into less parts and suppose that such a liquid part is between two dry parts of a dense body and sticking to them both becomes like a glew to hold them together will it not follow out of what we have said that these two dense parts will be as hard to be severed from one another as the small liquid part by which they stick together is to be divided So that when the viscuous ligaments which in a body hold together the dense parts are so small and subtile as no force we can apply can divide them the adhesion of the parts must needs grow then inseparable And therefore we use to moisten dry bodies to make them more easily be divided whereas those that are over-moist are of themselves ready to fall in pieces And thus you see how in general
continual application to the body it thus anatomises hath harden'd as it were rosted some parts into such greatness and driness as they will not flie nor can be carried up with any moderate heat But great quantity of fire being mingled with the subtiler parts of his baked earth makes them very pungent and acrimonious in tast so that they are of the nature of ordinary Salt and so called and by the help of water may easily be separated from the more gross parts which then remain a dead and useless earth By this discourse 't is apparent that fire has been the instrument which hath wrought all these parts of an entire body into the forms they are in for whiles it carried away the fiery parts it swel'd the watry ones and whiles it lifted up them it digested the Aerial parts and whiles it drove up the Oyle it baked the earth and salt Again all these retaining for the most part the proper nature of the substance from whence they are extracted 't is evident that the substance is not dissolv'd for so the n