a little more slowly For you may have observed that when it snows in the South Parts the flakes of Snow are not so great as in the North which is a probable sign they fall in the South from a greater height and consequently disperse themselves more as water does that falls down from a high and steep Rock A. 'T is not improbable B. In natural causes all you are to expect is but probability which is better yet then making Gravity the cause when the cause of Gravity is that you desire to know and better then saying the Earth draws it when the Question is how it draws A. Why does the Earth cast off Air more easily than it does Water or any other heavy bodies B. It is indeed the Earth that casteth off that Air which is next unto it But it is that Air which casteth off the next Air and so continually Air moveth Air which it can more easily do then any other thing because like bodies are more susceptible of one anothers motions as you may see in two Lute-strings equally strained what motion one string being stricken communicates to the Air the same will the other receive from the Air but strained to a differing note will be less or not at all moved For there is no body but Air that hath not some internal though invisible motion of its parts And it is that internal motion which distinguisheth all natural bodies one from another A. What is the cause why certain Squibs though their substance be either Wood or other heavy matter made hollow and filled with Gunpowder which is also heavy do nevertheless when the Gunpowder is kindled fly upwards B. The same that keeps a man that swims from sinking though he be heavier then so much water He keeps himself up and goes forward by beating back the water with his Feet and so does a Squib by beating down the Air with the stream of the fired Gunpowder that proceeding from its Tail makes it recoil A. Why does any Brass or Iron Vessel if it be hollow flote upon the water being so very heavy B. Because the Vessel and the Air in it taken as one body is more easily cast off than a body of water equal to it A. How comes it to pass that a Fish especially such a broad Fish as a Turbut or a Plaice which are broad and thin in the bottom of the Sea perhaps a mile deep is not press'd to death with the weight of water that lies upon the back of it B. Because all heavy bodies descend towards one point which is the Center of the Earth and consequently the whole Sea descending at once does arch it self so as that the upper parts cannot press the parts next below them A. It is evident Nor can there be possibly any weight as some suppose there is of a Cylinder of Air or Water or of any other liquid thing while it remains in its own Element or is sustained and inclosed in a Vessel by which one part cannot press the other CHAP. II. Problems of Tides A. WHat makes the Flux and Reflux of the Sea twice in a natural day B. We must come again to our Basen of water wherein you have seen whilst it was moved how the water mounteth up by the sides and withal goes circling round about Now if you should fasten to the inside of the Basen some bar from the bottom to the top you would see the water instead of going on go back again from that bar ebbing and the water on the other side of the bar to do the same but in counter-time and consequently to be highest where the contrary streams meet together and then return again marking out four quarters of the Vessel two by their meeting which are the high waters and two by their retiring which are the low waters A. What bar is that you find in the Ocean that stops the current of the water like that you make in the Basen B. You know that the main Ocean lies East and West between India and the Coast of America and again on the other side between America and India If therefore the Earth have such a motion as I have supposed it must needs carry the current of the Sea East and West In which course the bar that stoppeth it is the South part of America which leaves no passage for the water but the narrow Streight of Magellan The Tide rises therefore upon the Coast of America And the rising of the same in this part of the world proceedeth from the swelling chiefly of the water there and partly also from the North Sea which lieth also East and West and has a passage out of the South Sea by the Streight of Anian between America and Asia A. Does not the Mediterranean Sea lie also East and West why are there not the like Tides there B. So there are proportionable to their lengths and quantity of water A. At Genoa at Ancona there are none at all or not sensible B. At Venice there are and in the bottom of the Streights and a current all along both the Mediterranean-Sea and the Gulf of Venice And it is the current that makes the Tides unsensible at the sides but the check makes them visible at the bottom A. How comes it about that the Moon hath such a stroke in the business as so sensibly to encrease the Tides at Full and Change B. The motion I have hitherto supposed but in the Earth I suppose also in the Moon and in all those great Bodies that hang in the Air constantly I mean the Stars both fixed and errant And for the Sun and Moon I suppose the Poles of their motion to be the Poles of the Aequinoctial which supposed it will follow because the Sun the Earth and the Moon at every Full and Change are almost in one streight line that this motion of the Earth will be made swifter than in the Quarters For this motion of the Sun and Moon being communicated to the Earth that hath already the like motion maketh the same greater and much greater when they are all three in one streight line which is only at the Full and Change whose Tides are therefore called Spring Tides A. But what then is the cause that the Spring-Tides themselves are twice a year namely when the Sun is in the Equinoctial greater than at any other times B. At other times of the year the Earth being out of the Aequinoctial the motion thereof by which the Tides are made will be less augmented by so much as a motion in the obliquity of 23 degrees or thereabout which is the distance between the Aequinoctial and Ecliptick Circles is weaker then the motion which is without obliquity A. All this is reasonable enough if it be possible that such motions as you suppose in these bodies be really there But that is a thing I have some reason to doubt of For the throwing off of Air consequent to these motions is the cause
in pieces A. 'T is like enough to be so And if nature have betrayed her self in any thing I think it is in this and in that other experience of the Cross-bow which strongly and evidently demonstrates the internal reciprocation of the Motion which you suppose to be in the internal parts of every Hard body And I have observed somewhat in Looking-glasses which much confirms that there is some such Motion in the internal parts of Glass as you have supposed for the cause of Hardness For let the Glass be AB and let the Object at C be a Candle and the Eye at D. Now by divers Reflections and Refractions in the two superficies of the Glass if the Lines of Vision be very oblique you shall see many images of the Candle as E F G in such order and position as is here described But if you remove your Eye to C and the Candle to D they will appear in a situation manifestly different from this Which you will yet more plainly perceive if the Looking-Glass be coloured as I have observed in Red and Blew Glasses and could never conceive any probable cause of it till now you tell me of this secret Motion of the parts across the grain of the Glass acquired by cooling it this or that way B. There be very many kinds of Hard bodies Metals Stones and other kinds in the bowels of the Earth that have been there ever sence the beginning of the World and I believe also many different sorts of Juices that may be made Hard But for one general cause of Hardness it can be no other then such an internal Motion of parts as I have already described whatsoever may be the cause of the several concomitant qualities of their Hardness in particular A. We see water Hardened every Frosty day It 's likely therefore you may give a pribable cause of Ice What is the cause of Freezing of the Ocean towards the Poles of the Earth B. You know the Sun being always between the Tropicks and as we have supposed always casting off the Air and the Earth likewise casting it off from it's self there must needs on both sides be a great Stream of Air towards the Poles shaving the superficies of the Earth and Sea in the Northern and Southern Climates This shaving of the Earth and Sea by the Stream of Air must needs contract and make to shrink those little Circles of the internal parts of Earth and Water and consequently Harden them first at the superficies into a thin skin which is the first Ice and afterwards the same Motion continuing and the first Ice co-operating the Ice becomes thicker And this I conceive to be the cause of the Freezing of the Ocean A. If that be the cause I need not ask how a Bottle of water is made to Freeze in warm weather with Snow or Ice mingled with Salt For when the Bottle is in the midst of it the Wind that goeth out both of the Salt and of the Ice as they dissolve must needs shave the superficies of the Bottle and the Bottle work accordingly on the water without it and so give it first a thin skin and at last thicken it into a solid piece of Ice But how comes it to pass that water does not use to Freeze in a deep Pit B. A deep Pit is a very thick Bottle and such as the Air cannot come at but only at the top or where the Earth is very loose and spungy A. Why will not Wine Freeze as well as Water B. So it will when the Frost is great enough But the internal Motion of the parts of Wine and other Heating Liquors is in greater Circles and stronger then the Motion of the parts of water and therefore less easily to be Frozen especally quite through because those parts that have the strongest Motion retire to the center of the Vessel CHAP. VI. Problems of Rain Wind and other WEATHER A. WHat is the original cause of Rain and how is it generated B. The motion of the Air such as I have described to you already tending to the dis-union of the parts of the Air must needs cause a continual endeavour there being no possibility of Vacuum of whatsoever fluid parts there are upon the face of the Earth and Sea to supply the place which would else be empty This makes the water and also very small and loose parts of the Earth and Sea to rise and mingle themselves with the Air and to become mist and Clouds Of which the greatest quantity arise there where there is most water namely from the large parts of the Ocean which are the South Sea the Indian Sea and the Sea that divideth Europe and Africa from America over which the Sun for the greatest part of the year is perpendicular and consequently raiseth a greater quantity of water Which afterwards gathered into Clouds falls down in Rain A. If the Sun can thus draw up the water though but in small drops why can it not as easily hold it up B. It is likely it would also hold them up if they did not grow greater by meeting together nor were carried away by the Air towards the Poles A. What makes them gather together B. It is not improbable that they are carried against Hills and there stopt till more overtake them And when they are carried towards the North or South where the force of the Sun is more oblique and thereby weaker they descend gently by their own weight And because they tend all to the center of the Earth they must needs be united in their way for want of room and so grow bigger And then it Rains A. What is the reason it Rains so seldom but Snows so often upon very high Mountains B. Because perhaps when the water is drawn up higher then the highest Mountains where the course of the Air between the Aequator and the Poles is free from stopping the Stream of the Air Freezeth it into Snow And 't is in those places only where the Hills shelter it from that Stream that it falls in Rain A. Why is there so little Rain in Egypt and yet so much in other parts nearer the Aequinoctial as to make the Nile overflow the Countrey B. The cause of the falling of Rain I told you was the the stopping and consequently the collection of Clouds about great Mountains especially when the Sun is near the Aequinoctial and thereby draws up the water more potently and from greater Seas If you consider therefore that the Mountains in which are the springs of Nile lye near the Aequinoctial and are exceeding great and near the Indian Sea you will not think it strange there should be great store of Snow This as it melts makes the Rain of Nile to rise which in April and May going on toward Egypt arrived there about the time of the Solstice and overflow the Countrey A. Why should not the Nile then overflow that Countrey twice a year For it comes twice
directly but as the Rudder inclines to the stern so will the Ship turn But this is too well known to insist upon you have observed that the Rudders of the greatest Ships are not very broad but go deep into the Water whereas Western Barges though but small Vessels have their Rudders much broader which argues that the holding of Water from passing is the office of a Rudder and therefore to a Ship that draws much Water the Rudder is made deep accordingly and in Barges that draw little Water the Rudders as less deep must so much the more be extended in breadth A. What makes Snow B. The same cause which speaking of Hardness I supposed for the cause of Ice For the Stream of Air proceeding from That both the Earth and the Sun cast off the Air and consequently maketh a stream of Air from the Aequinoctial towards the Poles passing amongst the Clouds shaving those small drops of Water whereof the Clouds consist and congeals them as they do the Water of the Sea or of a River And these small frozen drops are that which we call Snow A. But then how are great drops frozen into Hailstones and that especially as we see they are in Summer B. It is especially in Summer and hot weather that the drops of Water which make the Clouds are great enough but it is then also that Clouds are sooner and more plentifully carryed up And therefore the current of the Air strengthned between the Earth and the Clouds becomes more swift and thereby freezeth the drops of Water not in the Cloud it self but as they are falling Nor does it freeze them throughly the time of their falling not permitting it but gives them only a thin coat of Ice as is manifest by their suddain dissolving A. Why are not somteimes also whole Clouds when pregnant and ready to drop frozen into one piece of Ice B. I belive they are so whensoever it Thunders A. But upon what ground do you believe it B. From the manner or kind of noise they make namely a crack which I see not how it can possibly be made by Water or any other soft Bodies whatsoever A. Yes the Powder they call Aurum Fulminans when throughly warm gives just such another crack as Thunder B. But why may not every small grain of that Aurum Fulminans by it self be heard though a heap of them together be soft as is any heap of Sand. Salts of all sorts are of the nature of Ice But Gold is dissolved into Aurum Fulminans by Nitre and other Salts And the least grain of it gives a little crack in the fire by it self And therefore when they are so warmed by degrees the crack cannot chuse but be very great A. But before it be Aurum Fulminans they use to wash away the Salt which they call dulcifying it and then they dry it gently by degrees B. That is they exhale the pure Water that is left in the Powder and leave the Salt behind to Harden with drying Other Powder made of Salts without any Gold in them will give a crack as great as Aurum Fulminans A very great Chymist of our times hath written that Salt of Tarter Salt-peter and a little Brimstone ground together into a Powder and dryed a few grains of that Powder will be made by the fire to give as great a Clap as a Musquet A. Me thinks it were worth your tryal to see what effect a Quart or a Pint of Aurum Fulminans would produce being put into a great Gun made strong enough on purpose and the Breech of the Gun set in hot Cinders so as to heat by degrees till the Powder fly B. I pray you try it your self I cannot spare so much Money A. What is it that breaketh the Clouds when they are frozen B. In very hot weather the Sun raiseth from the Sea and all moist places abundance of Water and to a great height And whilst this Water hangs over us in Clouds or is again descending it raiseth other Clouds and it hapens very often that they press the Air between them and squeeze it through the Clouds themselves very violently which as it passes shaves and hardens them in the manner declared A. That has already been granted my question is what breaks them B. I must here take in one supposition more A. Then your Basen it seems holds not all you have need of B. It may for all this for the supposition I add is no more but this that what internal motion I ascribe to the Earth and other the Concrete parts of the World is to be supposed also in every of their parts how small soever for what reason is there to think in case the whole Earth have in truth the motion I have ascribed to it that one part of it taken away the remaining part should love that motion If you break a Load-stone both parts will retain their vertue though weakened according to the diminution of their quantity I suppose therefore in every small part of the Earth the same kind of motion which I have supposed in the whole and so I recede not yet from my Basen A. Let it be supposed and withall that abundance of Earth which I see you aim at be drawn up together with the Water What then B. Then if many pregnant Clouds some ascending and some descending meet together and make concavities between and by the pressing out of the Air as I have said before become Ice those Atomes as I may call them of Earth will be by the straining of the Air through the water of the Clouds be left behind and remain in the Cavities of the Clouds and be more in number then for the proportion of the Air therein Therefore for want of liberty they must needs justle one another and become as they are more and more streightened of room more and more swift and consequently at last break the Ice suddenly and violently now in one place and by and by in another and make thereby so many claps of Thunder and so many Flashes of Lightning For the Air Recoiling upon our Eyes is that which maketh those Flashes to our Fancy A. But I have seen Lightning in a very clear Evening when there has been neither Thunder nor Clouds B. Yes in a clear evening because the Clouds and the Rain were below the Horison perhaps 40 or 50 Miles off so that you could not see the Clouds nor hear the Thunder A. If the Clouds be indeed Frozen into Ice I shall not wonder if they be sometimes also so scituated as like Looking-Glasses to make us see sometimes three or more Suns by Refraction and Reflection CHAP. VII Problems of Motion Perpendicular Oblique of Pression and Percussion Reflection and Refraction Attraction and Repulsion IF a Bullet from a certain point given be shot against a wall Perpendicularly and again from the same Point Oblique What will be the proportion of the Forces wherewith they urge the wall
that should drive them back B. For my part I believe the cause of their descending is not in any natural appetite of the bodies that descend but rather that the Globe of the Earth hath some special motion by the which it more easily casteth off the Air than it doth other bodies And then this descent of those we call heavy bodies must of necessity follow unless there be some empty spaces in the world to receive them For when the Air is thrown off from the Earth somewhat must come into the place of it in case the world be full and it must be those things which are hardliest cast off that is those things which we say are heavy A. But suppose there be no place empty for I will defer the Question till anon how can the Earth cast off either the Air or any thing else B. I shall shew you how and that by a familiar Example If you lay both your hands upon a Basen with water in it how little soever and move it circularly and continue that motion for a while and you shall see the water rise upon the sides and fly over by which you may be assured that there is a kind of circulating motion which would cast off such bodies as are contiguous to the body so moved A. I know very well there is and it is the same motion which Country people use to purge their Corn For the Chaff and Straws by casting the Grain to the side of the Seive will come towards the middle But I would see the Figure B. Here it is There is a Circle pricked out whose Center is A and three less Circles whose Centers are B C D let every one of them represent the Earth as it goeth from B to C and from C to D always touching the uttermost Circle and throwing off the Air as is marked at E and F. And if the world were not full there would follow by this scattering of the Air a great deal of space left empty But supposing the world full there must be a perpetual shifting of the Air one part into the place of another A. But what makes a stone come down suppose from G B. If the Air be thrown up beyond G it will follow that at the last if the motion be continued all the Air will be above G that is above the stone which cannot be till the stone be at the Earth A. But why comes it down still with encreasing swiftness B. Because as it descends and is already in motion it receiveth a new impression from the same cause which is the Air whereof as part mounteth part also must descend supposing as we have done the plenitude of the world For as you may observe by the Figure the motion of the Earth according to the Diameter of the uttermost Circle is progressive and so the whole motion is compounded of two motions one circular and the other progressive and consequently the Air ascends and circulates at once And because the stone descending receiveth a new pressure in every point of its way the motion thereof must needs be accelerated A. 'T is true For it will be accelerated equally in equal times and the way it makes will encrease in a double proportion to the times as hath heretofore been demonstrated by Galileo I see the solution now of an Experiment which before did not a little puzzle me You know that if two plummets hang by two strings of equal length and you remove them from the perpendicular equally I mean in equal angles and then let them go they will make their turns and returns together and in equal times And though the arches they describe grow continually less and less yet the times they spend in the greater arches will still be equal to the time they spend in the lesser B. 'T is true Do you find any Experiment to the contrary A. Yes For if you remove one of the plummets from the perpendicular so as for example to make an angle with the perpendicular of 80 degrees and the other so as to make an angle of 60 degrees they will not make their turns and returns in equal times B. And what say you is the cause of this A. Because the arches are the spaces which these two motions describe they must be in double proportion to their own times which cannot be unless they be let go from equal altitudes that is from equal angles B. 'T is right and the Experiment does not cross but confirm the equality of the times in all the arches they describe even from 90 degrees to the least part of one degree A. But is it not too bold if not extravagant an assertion to say the Earth is moved as a man shakes a Basen or a Seive Does not the Earth move from West to East every day once upon his own Center and in the Ecliptick Circle once a year And now you give it another odd motion How can all these consist in one and the same body B. Well enough If you be a Shipboard under sail do not you go with the Ship Cannot you also walk upon the Deck Cannot every drop of bloud move at the same time in your veins How many motions now do you assign to one and the same drop of bloud Nor is it so extravagant a thing to attribute to the Earth this kind of motion but that I believe if we certainly knew what motion it is that causeth the descent of bodies we should find it either the same or more extravagant But seeing it can be nothing above that worketh this effect it must be the Earth it self that does it and if the Earth then you can imagine no other motion to do it withal but this And you will wonder more when by the same motion I shall give you a probable account of the causes of very many other works of Nature A. But what part of the Heaven do you suppose the Poles of your pricked Circle point to B. I suppose them to be the same with the Poles of the Ecliptick For seeing the Axis of the Earth in this Nation and in the annual motion keeps parallel to it self the Axis must in both motions be parallel as to sense For the Circle which the Earth describes is not of visible magnitude at the distance it is from the Sun A. Though I understand well enough how the Earth may make a stone descend very swiftly under the Ecliptick or not far from it where it throws off the Air perpendicularly yet about the Poles of the Circle methinks it should cast off the Air very weakly I hope you will not say that bodies descend faster in places remote from the Poles than nearer to them B. No but I ascribe it to the like motion in the Sun and Moon For such motions meeting must needs cast the stream of the Air towards the Poles And then there will be the same necessity for the descent there that there is in other places though perhaps
you say that other things come to the Earth And therefore the like motions in the Sun and Moon and Stars casting off the Air should also cause all other things to come to every one of them From whence it will follow that the Sun Moon and Earth and all other bodies but Air should presently come together into one heap B. That does not follow For if two bodies cast off the Air the motion of that Air will be repress'd both ways and diverted into a course towards the Poles on both sides and then the two bodies cannot possibly come together A. 'T is true And besides this driving off the Air on both sides North and South makes the like motion of Air there also And this may answer to the Question How a stone could fall to the Earth under the Poles of the Ecliptick by the only casting off of Air B. It follows from hence that there is a certain and determinate distance of one of these bodies the Stars from another without any very sensible variation A. All this is probable enough if it be true that there is no Vacuum no place empty in all the World And supposing this motion of the Sun and Moon to be in the plain of the Aequinoctial methinks that this should be the cause of the Diurnal motion of the Earth And because this motion of the Earth is you say in the plain of the Aequinoctial the same should cause also a motion in the Moon on her own Center answerable to the Diurnal motion of the Earth B. Why not what else can you think makes the Diurnal motion of the Earth but the Sun And for the Moon if it did not turn upon its own Center we should see sometimes one sometimes another face of the Moon which we do not CHAP. III. Problems of Vacuum WHat convincing Argument is there to prove that in all the world there is no empty place B. Many but I will name but one and that is the difficulty of separating two bodies hard and flat laid one upon another I say the difficulty not the impossibility It is possible without introducing Vacuum to pull assunder any two bodies how hard and flat soever they be if the force used be greater than the resistance of the hardness And in case there be any greater difficulty to part them besides what proceeds from their hardness then there is to pull them further assunder when they are parted that difficulty is Argument enough to prove there is no Vacuum A. These Assertions need demonstration And first how does the difficulty of separation argue the Plenitude of all the rest of the world B. If two flat polish'd Marbles lie one upon another you see they are hardly separated in all points at one and the same instant and yet the weight of either of them it is enough to make them slide off one from the other Is not the cause of this that the Air succeeds the Marble that so slides and fills up the place it leaves A. Yes certainly What then B. But when you pull the whole Superficies assunder not without great difficulty what is the cause of that difficulty A. I think as most men do that the Air cannot fill up the space between in an instant For the parting is in an instant B. Suppose there be Vacuum in that Air into which the Marble you pull off is to succeed shall there be no Vacuum in the Air that was round about the two Marbles when they touched Why cannot that Vacuum come into the place between Air cannot succeed in an instant because a body and consequently cannot be moved through the least space in an instant But emptiness is not a body nor is moved but made by the act it self of separation There is therefore if you admit Vacuum no necessity at all for the Air to fill the space left in an instant And therefore with what ease the Marble coming off presseth out the Vacuum of the Air behind it with the same ease will the Marbles be pulled assunder Seeing then if there were Vacuum there would be no difficulty of Separation it follows because there is difficulty of separation that there is no Vacuum A. Well now supposing the world full how do you prove it possible to pull those Marbles assunder B. Take a piece of soft wax Do not you think the one half touches the other half as close as the smoothest Marbles yet you can pull them assunder But how still as you pull the wax grows continually more and more slender there being a perpetual parting or discession of the outermost part of the wax one from another which the Air presently fills and so there is a continual lessening of the wax till it be no bigger than a hair and at last separation If you can do the same to a Pillar of Marble till the outside give way the effect will be the same but much quicker after it once begins to break in the Superficies because the force that can master the first resistance of the hardness will quickly dispatch the rest A. It seems so by the brittleness of some hard bodies But I shall afterward put some Questions to you touching the nature of hardness But now to return to our subject What reason can you render without supposing Vacuum of the effects produced in the Engine they use at Gresham Colledge B. That Engine produceth the same effects that a strong wind would produce in a narrow room A. How comes the wind in You know the Engine is a hollow round pipe of brass into which is thrust a Cylinder of wood covered with Leather and fitted to the Cylinder so exactly as no Air can possibly pass between the leather and the brass B. I know it and that they may thrust it up there is a hole left in the Cylinder to let the Air out before it which they can stop when they please There is also in the bottom of the Cylinder a passage into a hollow Globe of Glass which passage they can also open and shut at pleasure And at the top of that Globe there is a wide mouth to put in what they please to try conclusions on and that also to be opened and shut as shall be needful 'T is of the nature of a Pop-gun which Children use but great costly and more ingenious They thrust forward and pull back the wooden Cylinder because it requires much strength with an Iron screw What is there in all this to prove the possibility of Vacuum A. When this wooden Cylinder covered with leather fit and close is thrust home to the bottom and the holes in the hollow Cylinder of Brass close stopped how can it be drawn back as with the screw they draw it but that the space it leaves must needs be empty For it is impossible that any Air can pass into the place to fill it B. Truly I think it close enough to keep out Straw and Feathers but not to keep out Air nor
empty space in the Vial before it was sucked And then why does not the water rise to fill that when a man sucks the Vial he draws nothing out neither into his Belly nor into his Lungs nor into his Mouth only he sets the Air within the glass into a circular motion giving it at once an endeavour to go forth by the sucking and an endeavour to go back by not receiving it into his mouth And so with a great deal of labour glues his lips to the neck of the Vial. Then taking it off and dipping the neck of the Vial into the water before the circulation cease the Air with the endeavour it hath now gotten pierces the water and goes out And so much Air as goes out so much matter comes up into the room of it CHAP. IIII. Problems of Heat and Light A. WHat is the cause of Heat B. How know you that any thing is Hot but your self A. Because I perceive by sense it Heats me B. It is no good argument The thing Heats me therefore it is Hot. But what alteration do you find in your body at any time by being Hot A. I find my skin more extended in Summer than in Winter and am sometimes fainter and weaker then ordinary as if my Spirits were exhaled and I sweat B. Then that is it you would know the cause of I have told you before that by the motion I suppose both in the Sun and in the Earth the Air is dissipated and consequently that there would be an infinite number of small empty places but that the World being full there comes from the next parts other Air into the spaces they would else make empty When therefore this motion of the Sun is excercised upon the Superficies of the Earth if there do not come out of the Earth it self some corporal substance to supply that tearing of the Air we must return again to the admission of Vacuum If there do then you see how by this motion fluid bodies are made to exhale out of the Earth The like happens to a mans body or hand which when he perceives he says he is Hot. And so of the Earth when it sendeth forth Water and Earth together in Plants we say it does it by Heat from the Sun A. 'T is very probable and no less probable that the same action of the Sun is that which from the Sea and moist places of the Earth but especially from the Sea fetcheth up the water into the Clouds But there be many ways of Heating besides the action of the Sun or of Fire Two pieces of Wood will take Fire if in Torning they be prest together B. Here again you have a manifest laceration of the Air by the reciprocal and contrary motions of the two pieces of wood which necessarily causeth a coming forth of whatsoever is Aereal or fluid within them and the motion pursued a dissipation also of the other more solid parts into Ashes A. How comes it to pass that a man is warmed even to sweating almost with every extraordinary labour of his body B. It is easie to understand how by that labour all that is liquid in his body is tossed up and down and thereby part of it also cast forth A. There be some things that make a man Hot without sweat or other evaporation as Caustiques Nettles and other things B. No doubt But they touch the part they so Heat and cannot work that effect at any distance A. How does Heat cause light and that partially in some bodies more in some less though the Heat be equal B. Heat does not cause Light at all But in many Bodies the same cause that is to say the same motion causeth both together so that they are not to one another as cause and effect but are concomitant Effects sometimes of one and the same motion A. How B. You know the rubbing or heard pressing of the Eye or a stroke upon it makes an apparition of Light without and before it which way soever you look This can proceed from nothing else but from the restitution of the Organ pressed or stricken unto its former ordinary situation of parts Does not the Sun by his thrusting back the Air upon your eyes press them Or does not those bodies whereon the Sun shines though by reflection do the same though not so strongly And do not the Organs of Sight the Eye the Heart and Brains resist that pressure by an endeavour of restitution outwards Why then should there not be without and before the Eye an apparition of Light in this case as well as in the other A. I grant there must But what is that which appears after the pressing of the eye For there is nothing without that was not there before or if there were methinks another should see it better or as well as he or if in the dark methinks it should enlighten the place B. It is a fancy such as is the appearance of your face in a Looking-glass such as is a Dream such as is a Ghost such as is a spot before the Eye that hath stared upon the Son or Fire For all these are of the Regiment of Fancy without any body concealed under them or behind them by which they are produced A. And when you look towards the Sun or Moon why is not that also which appears before your Eyes at that time a fancy B. So it is Though the Sun it self be a real Body yet that bright Circle of about a foot Diameter cannot be the Sun unless there be two Suns a greater and a lesser And because you may see that which you call the Sun both above you in the Skie and before you in the Water and two Suns by distorting your Eye in two places of the Skie one of them must needs be Fancy And if one both All sense is Fancy though the cause be always in a real Body A. I see by this that those things which the Learned call the Accidents of Bodies are indeed nothing else but diversity of Fancy and are inherent in the Sentient and not in the Objects except Motion and Quantity And I perceive by your Doctrine you have been tampering with Leviathan But how comes Wood with a certain degree of Heat to shine and Iron also with a greater degree but no Heat at all to be able to make water shine B. That which shineth hath the same Motion in its parts that I have all this while supposed in the Sun and Earth In which Motion there must needs be a competent degree of swiftness to move the sense that is to make it visible All Bodies that are not fluid will shine with Heat if the Heat be very great Iron will shine and Gold will shine but water will not because the parts are carried away before they attain to that degree of swiftness which is requisite A. There are many fluid Bodies whose parts evaporate and yet they make a flame as Oyl and Wine and other
strong drinks B. As for Oyl I never saw any inflamed by it self how much soever Heated therefore I do not think they are the parts of the Oyl but of the combustible body oyled that shine but the parts of Wine and strong Drinks have partly a strong Motion of themselves and may be made to shine but not with boiling but by adding to them as they rise the flame of some other body A. How can it be known that the particles of Wine have such a Motion as you suppose B. Have you ever been so much distempered with drinking Wine as to think the Windows and Table move A. I confess though you be not my Confessor I have but very seldom and I remember the window seemed to go and come in a kind of circling Motion such as you have described But what of that B. Nothing but that it was the Wine that caused it which having a good degree of that Motion before did when it was Heated in the Veins give that concussion which you thought was in the window to the Veins themselves and by the continuation of the parts of mans Body to the Brain and that was it which made the window seem to move A. What is Flame For I have often thought the Flame that comes out of a small heap of Straw to be more before it hath done Flaming then a hundred times the Straw it self B. It was but your Fancy If you take a stick in your hand by one end the other end burning and move it swiftly the burning end if the Motion be circular shall seem a circle if streight a streight line of Fire longer or shorter according to the swiftness of the Motion or to the space it moves in You know the cause of that A. I think it is because the impression of that visible Object which was made at the first instant of the Motion did last till it was ended For then it will follow that it must be visible all the way the impressions in all points of the time being equal B. The cause can be no other The smallest spark of Fire flying up seems a line drawn upward and again by that swift circular Motion which we have supposed for the cause of Light seems also broader then it is And consequently the Flame of every thing must needs seem much greater then it is A. What are those sparks that flie out of the Fire B. They are small pieces of the wood or Coals or other Fuel loosened and carried away with the Air that cometh up with them And being extiguished before their parts be quite dissipated into others are so much Soot and black and may be fired again A. A Spark of Fire may be stricken out of a cold stone It is not therefore Heat that makes this shining B. No 'T is the Motion that makes both the Heat and shining and the stroke makes the Motion For every of those Sparks is a little parcel of the stone which swiftly moved imprinteth the same Motion into the matter prepared or fit to receive it A. How comes the Light of the Sun to burn almost any combustible matter by rerefraction through a convex glass and by reflection from a concave B. The Air moved by the Sun presseth the convex glass in such manner as the action continued through it proceedeth not in the same streight line by which it proceeded from the Sun but tendeth more toward the center of the body it enters Also when the action is continued through the convex body it bendeth again the same way By which means the whole action of the Sun-beams are enclosed within a very small compass in which place therefore there must be a very vehement Motion and consequently if there be in that place combustible matter such as is not very hard kindle the parts of it will be dissipated and receive that Motion which worketh on the Eye as other Fire does The same reason is to be given for burning by Reflection For there also the Beams are collected into almost a point A. Why may not the Sun-beams be such a Body as we call Fire and pass through the pores of the glass so disposed as to cary them to a point or very near B. Can there be a glass that is all pores If there cannot then cannot this effect be produced by the passing of Fire through the pores You have seen men llght their Tobacco at the Sun with a burning glass or with a ball of Cristal held which way they will indifferently Which must be impossible unless the ball were all pores Again neither you nor I can conceive any other Fire then we have seen nor then such as water will put out But not only a solid Globe of Glass or Cristal will serve for a burning Glass but also a hollow one filled with water How then does the Fire from the Sun pass through the glass of water without being put out before it come to the matter they would have it burn A. I know not There comes nothing from the Sun If there did there is come so much from it already that at this day we had had no Sun CHAP. V. Problems of Hard and Soft A. WHat call you Hard and what Soft B. That body whereof no one part is easily put out of its place without removing the whole is that which I and all men call Hard and the contrary Soft So that they are but degrees one of another A. What is the cause that makes one body Harder then another or seeing you say they are but degrees of one another what makes one body Softer then another and the same body sometimes Harder sometimes Softer B. The same Motion which we have supposed from the beginning for the cause of so many other effects Which Motion not being upon the center of the part moved but the part it self going in another circle to and again it is not necessary that the Motion be perfectly circular For it is not circulation but the reciprocation I mean the to and again that does cast off and lacerrate the Air and consequently produce the fore-mentioned effects For the cause therefore of Hardness I suppose the reciprocation of Motion in those things which are Hard to be very swift and in very small circles A. This is somewhat hard to believe I would you could supply it with some visible experience B. When you see for example a Cross-bow bent do you think the parts of it stir A. No. I am sure they do not B. How are you sure You have no argument for it but that you do not see the Motion When I see you sitting still must I believe there is no Motion in your parts within when there are so many arguments to convince me there is A. What argument have you to convince me that there is Motion in a Cross-bow when it stands bent B. If you cut the string or any way set the Bow at liberty it will have then a very visible Motion What