by its dissolution transfers its Hardness to the water within B. You are merry But supposing as I do that the Ice in the Pail is more than the water in the Vessel you will finde no absurdity in the Argument Besides the Experiment you know is common A. I confess it is probable The Greeks have the word 〈◊〉 〈◊〉 〈◊〉 〈◊〉 〈◊〉 whence the Latins have their word Frigus to signifie the curling of water by the Wind and use the same also for Horrour which is the passion of one that cometh suddenly into a cold Air or is put into a sudden affright whereby he shrinks and his hair stands upright Which manifestly shews that the Motion which causeth Cold is that which pressing the Superficies of a Body sets the parts of it closer together But to proceed in my Quaeries Monsieur Des Cartes who you know hath written somewhere that the noise we hear in Thunder proceeds from breaking of the Ice in the Clouds What think you of it Can a Cloud be turned into Ice B. Why not A Cloud is but Water in the Air. A. But how For he has not told us that B. You know that 't is onely in Summer and in hot weather that it Thunders or if in Winter it is taken for a Prodigie You know also that of Clouds some are higher some lower and many in number as you cannot but have oftentimes observed with spaces between them Therefore as in all Currents of water the Water is there swiftest where it is streightned with Islands so must the Current of Air made by the Annual Motion be swiftest there where it is checkt with many Clouds through which it must as it were be strained and leave behinde it many small particles of earth always in it and in hot weather more than ordinary A. This I understand and that it may cause Ice But when the Ice is made how is it broken And why falls it not down in shivers B. The particles are inclosed in small Caverns of the Ice and their Natural Motion being the same which we have ascribed to the Globe of the Earth requires a sufficient space to move in But when it is imprisoned in a less room that that then a great part of the Ice breaks And this is the Thunder-clap The Murmur following is from the settling of the Air. The Lightening is the fancie made by the recoiling of the Air against the Eye The fall is in Rain not in Shivers because the prisons which they break are extreme narrow and the shivers being small are dissolved by the Heat But in less Heat they would fall in Drops of Hail that is to say half frozen by the shaving of the Air as they fall and be in a very little time much less than Snow or Ice dissolved A. Will not that Lightning burn B. No. But it hath often kill'd men with Cold. But this extraordinary swiftness of Lightning consisteth not in the Expansion of the Air but in a straight and direct stream from where it breaks forth which is in many places successively according to the Motion of the Cloud A. Experience tells us that I have now done with my Problems concerning the great Bodies of the world the Stars and Element of Air in which they are moved and am therein satisfied and the rather because you have answered me by the Supposition of one onely Motion and commonly known and the same with that of Copernicus whose Opinion is received by all the Learned and because you have not used any of these empty terms Sympathy Antipathy Antiperistasis c. for a natural Cause as the old Philosophers have done to save their credit For though they were many of them wise men as Plato Aristotle Seneca and others and have written excellently of Morals and Politiques yet there is very little Natural Philosophy to be gathered out of their Writings B. Their Ethiques and Politiques are pleasant reading but I finde not any argument in their discourses of Justice or Vertue drawn from the supreme Authority on whose Laws all Justice Vertue and good Politiques depend A. Concerning this Cover or as some have called it the Scurf or Scab of the Terrestrial Star I will begin with you to morrow For it is a large Subject containing Animals Vegetables Metals Stones and many other kinds of Bodies the knowledge whereof is desired by most men and of the greatest and most general profit B. And this is it in which I shall give you the least satisfaction so great is the variety of Motion and so concealed from humane senses CAP. VII Of Hard and Soft and of the Atomes that flie in the Air. A. COncerning this Cover of the Earth made up of an infinite number of parts of different natures I had much ado to finde any tolerable method of enquiry But I resolved at last to begin with the Questions concerning Hard and Soft and what kinde of Motion it is that makes them so I know that in any pulsion of Air the parts of it go innumerable and inexplicable ways but I ask only if every point of it be moved B. No. If you mean a Mathematical point you know it is impossible For nothing is movable but Body But I suppose it divisible as all other Bodies into parts divisible For no Substance can be divided into Nothings A. Why may not that Substance within our Bodies which are called Animal spirits be another kind of Body and more subtile than the common Air B. I know not why no more than you or any man else knows why it is not very Air though purer perhaps than the common Air as being strained through the blood into the Brain and Nerves But howsoever that be there is no doubt but the least parts of the common Air respectively to the whole will easilier pierce with equal Motion the Body that resisteth them than the least parts of water For it is by Motion onely that any mutation is made in any thing and all things standing as they did will appear as they did And that which changeth Soft into Hard must be such as makes the parts not easily to be moved without being moved all together which cannot be done but by some Motion compounded And we call Hard that whereof no part can be put out of order without disordering all the rest which is not easily done A. How Water and Air beaten into extreme small Bubbles is hardned into Ice you have told me already and I understand it But how a soft Homogeneous Body as Air or Water should be so hardned I cannot imagine B. There is no hard Body that hath not also some degree of Gravity and consequently being loose there must be some Efficient Cause that is some Motion when it is severed from the Earth to bring the same to it again And seeing this compounded Motion gives to the Air and Water an Endeavour from the Earth the Motion which must hinder it must be in a way contrary to the compounded
every way and also continually change place to fill up the places forsaken by other parts of the Air which else would be empty there being no Vacuum to retire unto So that there would be a perpetual stream of Air and in a contrary way to the Motion of the Suns Body such as is the Motion of Water by the sides of a Ship under sail A. But this Motion of the Earth from West to East is onely Circular such as is described by a Compass about a Centre and cannot therefore repel the Air as the Sun does And the Disciples of Copernicus will have it to be the Cause of the Moons monthly motion about the Earth B. And I think Copernicus himself would have said the same if his purpose had been to have shewn the Natural Causes of the Motions of the Stars But that was no part of his designe which was onely from his own observations and those of former Astronomers to compute the times of their Motions partly to foretel the Conjunctions Oppositions and other Aspects of the Planets and partly to regulate the times of the Churches Festivals But his followers Kepler and Galileo make the Earths Motion to be the Efficient Cause of the Monthly motion of the Moon about the Earth which without the like Motion to that of the Sun in LM is impossible Let us therefore for the present take it in as a necessary Hypothesis which from some Experiment that I shall produce in our following discourses may prove to be a certain truth A. But seeing A is the Centre both of the Suns Body and of the Annual Motion of the Earth How can it be as all Astronomers say it is that the Orb of the Annual Motion of the Earth should be Excentrique to the Suns Body For you know that from the Vernal Aequinox to the Autumnal there be 187 days but from the Autumnal Aequinox to the Vernal there be but 178 days What Natural Cause can you assigne for this Excentricity B. Kepler ascribes it to a Magnetique vertue viz. that one part of the Earths Superficies has a greater kindness for the Sun than the other part A. I am not satisfied with that It is Magical rather than Natural and unworthy of Kepler Tell me your own opinion of it B. I think that the Magnetical vertue he speaks of consisteth in this that the Southern Hemisphere of the Earth is for the greatest part Sea and that the greatest part of the Northern Hemisphere is dry Land But how it is possible that from thence should proceed the Excentricity the Sun being neerest to the Earth when he is in the Winter-Solstice I shall shew you when we come to speak of the Motions of Air and Water A. That 's time enough For I intend it for our next meeting In the mean time I pray you tell me what you think to be the Cause why the Equinoctial and consequently the Solstitial points are not always in one and the same point of the Ecliptique of the Fixt Stars I know they are not because the Sun does not rise and set in points diametrally opposite For if it did there would be no difference of the Seasons of the year B. The cause of that can be no other than that the Earth which is l m hath the like Motion to that which I suppose the Sun to have in L M compounded of streight and circular from West to East in a day as the Annual Motion hath in a year so that not reckoning the Excentricity it will be moved through the Ecliptiques one Revolution as Copernicus proveth about one degree Suppose then the whole Earth moved from H to I which is half the year circularly but falling from I to i in the same time about 30 minutes and as much in the other Hemisphere from H to k then draw the line i k which will be equal and parallel to H I and be the Diameter of the Aequator for the next year But it shall not cut the Diameter of the Ecliptick B Z in A which was the Equinoctial of the former year but in o 36 seconds from the first degree of Aries Suppose the same done in the Hemisphere under the Plain of the paper and so you have the double of 36 seconds that is 72 seconds or very neer for the progress of the Vernal Equinox in a year The cause why I suppose the Arch I i to be half a degree in the Ecliptique of the Earth is that Copernicus and other Astronomers and Experience agree in this that the Aequinoctial points proceed according to the order of the Signes Aries Taurus Gemini c. from West to East every 100 year one degree or very neer A. In what time do they make the whole Revolution through the Ecliptique of the Sky B. That you may reckon For we know by Experience that it hath proceeded about one degree that is 60 minutes constantly a long time in a hundred years But as 100 years to one degree so is 36000 years to 360 degrees Also as 100 years to one degree so is one year to the hundred part of one degree or 60 minutes which is 60 100 or 36 seconds for the progress of one year which must be somewhat more than a degree according to Copernicus who lib. 3. cap. 2. saith That for 400 years before Ptolomie it was one degree almost constantly Which is well enough as to the Natural Cause of the Precession of the Aequinoctial points which is the often-said compounded Motion though not an exact Astronomical Calculation A. And 't is a great signe that his Supposition is true But what is the Cause that the Obliquity of the Ecliptique that is the distance between the Aequinoctial and the Solstice is not always the same B. The necessity of the Obliquity of the Ecliptique is but a consequence to the Precession of the Aequinoctial points And therefore if from C the North-Pole you make a little Circle C u equal to 15 minutes of a degree upon the Earth and another u s equal to the same which will appear like this Figure 8 that is as Copernicus calls it a Circle twined the Pole C will be moved half the time of the Aequinoctial points in the arc C u and as much in the alternate arc u s descending to s. But in the arc s u and its alternate rising to C. The cause of the twining is the Earths Annual Motion the same way in the Ecliptique and makes the four quarters of it and makes also their revolution twice as slow as that of the Aequinoctial points And therefore the Motion of it is the same compounded Motion which Copernicus takes for his Supposition and is the cause of the Precession of the Aequinoctial points and consequently of the variation of the Obliquity adding to it or taking from it somewhere more somewhere less so as that one with another the addition is not much more nor the substraction much less than 30 minutes But as
for the Natural Efficient cause of this compounded Motion either in the Sun or the Earth or any other Natural Body it can be none but the immediate hand of the Creator A. By this it seems that the Poles of the Earth are always the same but make this 8 in the Sphere of the fixt Stars neer that which is called Cynosura B. No 'T is described on the Earth but the Annual Motion describes a Circle in the Sphere of the fixed Stars Though I think it improper to say a Sphere of the fixt Stars when 't is so unlikely that all the fixt Stars should be in the Superficies of one and the same Globe A. I do not believe they are B. Nor I since they may seem less one than another as well by their different distances as by their different magnitudes Nor is it likely that the Sun which is a fixt Star is the Efficient Cause of the Motion of those remoter Planets Mars Jupiter and Saturn seeing the whole Sphere whose Diameter is the distance between the Sun and the Earth is but a point in respect of the distance between the Sun and any other fixed Star Which I say onely to excite those that value the knowledge of the Cause of Comets to look for it in the Dominion of some other Sun than that which moveth the Earth For why may not there be some other fixed Star neerer to some Planet than is the Sun and cause such a light in it as we call a Comet A. As how B. You have seen how in high and thin Clouds above the Earth the Sun-beams piercing them have appeared like a Beard and why might not such a Beard have appeared to you like a Comet if you had lookt upon it from as high as some of the fixed Stars A. But because it is a thing impossible for me to know I will proceed in my own way of enquiry And seeing you ascribe this compounded Motion to the Sun and Earth I would grant you that the Earth whose Annual Motion is from West to East shall give the Moon her Monthly-motion from East to West But then I ask you whether the Moon have also that compounded Motion of the Earth and with it a Motion upon its own Centre as hath the Earth For seeing the Moon has no other Planet to carry about her she needs it not B. I see reason enough and some necessity that the Moon should have both those Motions For you cannot think that the Creator of the Stars when he gave them their Circular Motion did first take a Centre and then describe a Circle with a Chain or Compass as men do No he moved all the parts of a Star together and equally in the Creation And that 's the reason I give you The necessity of it comes from this Phaenomenon that the Moon doth turn one and the same face towards the Earth Which cannot be by being moved about the Earth parallelly unless also it turn about its own Centre Besides we know by experience that the Motion of the Moon doth adde not a little to the Motion of the Sea Which were impossible if it did not adde to the Stream of the Air and by consequence to that of the Water A. If you could get a piece of the true and intimate Substance of the Earth of the bigness of a Musquet-bullet do you believe that the Bullet would have the like compounded Motion to that which you attribute to the Sun Earth and Moon B. Yes truly but with less strength according to its magnitude saving that by its Gravity falling to the Earth the activity of it would be unperceived A. I will trouble you no more with the Nature of Celestial appearances But I pray you tell me by what art a man may finde what part of a Circle the Diameter of the Suns Body doth subtend in the Ecliptique Circle B. Kepler says it subtends 30 minutes which is half a degree His way to finde it is by letting in the Sun-beams into a close room through a small hole and receiving the image of it upon a plain perpendicularly For by this means he hath a Triangle whose sides and angles he can know by measure and the vertical Angle he seeks for and the substance of the arc of the Suns Body A. But I think it impossible to distinguish where the part illuminate toucheth the part not illuminate B. Another way is this Upon the Aequinoctial-day with a Watch that shews the minutes standing by you observe when the lower brim of the Suns setting first comes to the Horizon and set the Index to some minute of the Watch and observe again the upper brim when it comes to the Horizon then count the minutes and you have what you look for Other way I know none CAP. V. Of the Motions of Water and Air. A. I Have considered as you bad me this compounded Motion with great admiration First it is that which makes the difference between Continuum and Contiguum which till now I never could distinguish For Bodies that are but Contiguous with any little force are parted but by this compounded Motion because every point of the body makes an equal Line in equal time and every Line crosses all the rest one part cannot be separated from another without disturbing the Motion of all the other parts at once And is not that the Cause think you that some Bodies when they are prest or bent as soon as the force is removed return again of themselves to their former figure B. Yes sure saving that it is not of themselves that they return for we were agreed that nothing can move it self but it is the Motion of the parts which are not prest that delivers those that are And this restitution the Learned now call the Spring of a Body The Greeks called it Antitypia A. When I considered this Motion in the Sun and the Earth and Planets I fancied them as so many Bodies of the Army of the Almighty in an immense field of Air marching swiftly and commanded under God by his glorious Officer the Sun or rather forced so to keep their order in every part of every of those Bodies as never to go out from the distance in which he had set them B. But the parts of the Air and other Fluids keep not their places so A. No. You told me that this Motion is not natural in the Air but received from the Sun B. True But since we seek the Natural Causes of Sublunary Effects where shall we begin A. I would fain know what makes the Sea to ebbe and flow at certain Periods and what causeth such variety in the Tides B. Remember that the Earth turneth every day upon its own Axis from West to East and all the while it so turneth every point thereof by its compounded Motion makes other Circlings but not on the same Centre which is you know a rising in one part of the day and a falling in the other part What
think you must happen to the Sea which resteth on it and is a Fluid Body A. I think it must make the Sea rise and fall And the same happeneth also to the Air from the Motion of the Sun B. Remember also in what manner the Sea is situated in respect of the Dry Land A. Is not there a great Sea that reacheth from the Straight of Magellan Eastward to the Indies and thence to the same Straight again And is not there a great Sea called the Atlantick Sea that runneth Northward to us and does not the great South-Sea run also up into the Northern Seas But I think the Indian and the South-Sea of themselves to be greater than all the rest of the Surface of the Globe B. How lieth the water in those two Seas A. East and West and rises and falls a little as it is forc'd to do by this compounded Motion which is a kind of succussion of the Earth and fills both the Atlantick and Northern Seas B. All this would not make a visible difference between High and Low water because this Motion being so regular the unevenness would not be great enough to be seen For though in a Bason the water would be thrown into the Air yet the Earth cannot throw the Sea into the Air. A. Yes The Bason if gently moved will make the water so move that you shall hardly see it rise B. It may be so But you should never see it rise as it doth if it were not checkt For at the Straight of Magellan the great South-Sea is checkt by the shore of the Continent of Peru and Chily and forced to rise to a great height and made to run up into the Northern Seas on that side by the coast of China and at the return is checkt again and forced through the Atlantick into the British and German Seas And this is done every day For we have supposed that the Earths Motion in the Ecliptique caused by the Sun is Annual and that its Motion in the Aequinoctial is Diurnal It followeth therefore from this compounded Motion of the Earth the Sea must Ebb and Flow twice in the space of Twenty four hours or thereabout A. Has the Moon nothing to do in this business B. Yes For she hath also the like Motion And is though less swift yet much neerer to the Earth And therefore when the Sun and Moon are in Conjunction or Opposition the Earth as from two Agents at once must needs have a greater Succussion And if it chance at the same time the Moon also be in the Ecliptique it will be yet greater because the Moon then worketh on the Earth less obliquely A. But when the Full or New Moon happen to be then when the Earth is in the Aequinoctial points the Tides are greater than ordinary Why is that B. Because then the force by which they move the Sea is at that time to the force by which they move the same at other times as the Aequinoctial Circle to one of its Parallels which is a lesser Circle A. 'T is evident And 't is pleasant to see the Concord of so many and various motions when they proceed from one and the same Hypothesis But what say you to the stupendious Tides which happen on the Coasts of Lincolnshire on the East and in the River of Severn on the West B. The cause of that is their proper Scituation For the Current of the Ocean through the Atlantick Sea and the Current of the South-Sea through the Northern Seas meeting together raise the water in the Irish and British Seas a great deal higher than ordinary Therefore the mouth of the Severn being directly opposite to the Current from the Atlantick Sea and those Sands on the Coast of Lincolnshire directly opposite to the Current of the German Sea those Tides must needs fall furiously into them by this Succussion of the water A. Does when the Tide runs up into a River the water all rise together and fall together when it goes out No One part riseth and another falleth at the same time because the Motion of the Earth rising and falling is that which makes the Tide A. Have you any Experiment that shews it B. Yes You know that in the Thames it is high water at Greenwich before it is high water at London-bridge The water therefore falls at Greenwich whilst it riseth all the way to London But except the top of the water went up and the lower part downward it were impossible A. 'T is certain It is strange that this one Motion should salve so many apparences and so easily But I will produce one Experiment of water not in the Sea but in a Glass If you can shew me that the cause of it is this compounded Motion I shall go neer to think it the Cause of all other Effects of Nature hitherto disputed of The Experiment is common and described by the Lord Chancellour Bacon in the third page of his Natural History Take saith he a Glass of water and draw your finger round about the lip of the Glass pressing it somewhat hard after you have done so a few times it will make the water frisk up into a fine Dew After I had read this I tried the same with all diligence my self and found true not onely the frisking of the water to above an inch high but also the whole Superficies to circulate and withal to make a pleasant sound The Cause of the frisking he attributes to a tumult of the inward parts of the Substance of the Glass striving to free it self from the pressure B. I have tried and found both the Sound and Motion and do not doubt but the pressure of the parts of the Glass was part of the Cause But the Motion of my finger about the Glass was always parallel and when it chanced to be otherwise both Sound and Motion ceased A. I found the same And being satisfied I proceed to other questions How is the water being a heavie Body made to ascend in small particles into the Air and be there for a time sustained in form of a Cloud and then fall down again in Rain B. I have shewn already that this compounded Motion of the Sun in one part of its Circumlation drives the Air one way and in the other part the contrary way and that it cannot draw it back again no more than he that sets a stone a flying can pull it back The Air therefore which is contiguous to the water being thus distracted must either leave a Vacuum or else some part of the water must rise and fill the spaces continually forsaken by the Air. But that there is no Vacuum you have granted Therefore the water riseth into the Air and maketh the Clouds and seeing they are very small and invisible parts of the water are though naturally heavie easily carried up and down with the Wind till meeting with some Mountain or other Clouds they be prest together into greater drops and
fall by their weight So also it is forced up in moist ground and with it many small Atomes of the Earth which are either twisted with the rising water into Plants or are carried up and down in the Air incertainly But the greatest Quantity of Water is forced up from the great South and Indian Seas that lie under the Tropique of Capricorn And this Climate is that which makes the Suns Perigaeum to be always on the Winter-Solstice And that is the part of the Terrestrial Globe which Keplerus says is kinde to the Sun whereas the other part of the Globe which is almost all dry land has an Antipathy to the Sun And so you see where this Magnetical vertue of the Earth lies For the Globe of the Earth having no Natural Appetite to any place may be drawn by this Motion of the Sun a little neerer to it together with the water which it raiseth A. Can you guess what may be the Cause of Wind B. I think it manifest that the unconstant Winds proceed from the uncertain Motion of the Clouds ascending and descending or meeting with one another For the Winds after they are generated in any place by the descent of a Cloud they drive other Clouds this way and that way before them the Air seeking to free it self from being pent up in a straight For when a Cloud descendeth it makes no wind sensible directly under it self But the Air between it and the Earth is prest and forced to move violently outward For it is a certain Experiment of Mariners that if the Sea go high when they are becalmed they say they shall have more Wind than they would and take in their Sails all but what is necessary for steering They know it seems that the Sea is moved by the descent of Clouds at some distance off Which presseth the water and makes it come to them in great Waves For a Horizontal Wind does but curl the Water A. From whence come the Rivers B. From the Rain or from the falling of Snow on the higher ground But when it descendeth under ground the place where it again ariseth is called the Spring A. How then can there be a Spring upon the top of a Hill B. There is no Spring upon the very top of a Hill unless some Natural Pipe bring it thither from a higher Hill A. Julius Scaliger says there is a River and in it a Lake upon the top of Mount Cenis in Savoy and will therefore have the Springs to be ingendred in the Caverns of the Earth by Condensation of the Air. B. I wonder he should say that I have pass'd over that Hill twice since the time I read that in Scaliger and found that River as I pass'd and went by the side of it in plain ground almost two miles Where I saw the water from two great Hills one on one side the other on the other in a thousand small Rillets of melting Snow fall down into it Which has made me never to use any Experiment the which I have not my self seen As for the conversion of Air into Water by Condensation and of Water into Air by Rarefaction though it be the doctrine of the Peripatetiques it is a thing incogitable and the words are insignificant For by Densum is signified onely frequencie and closeness of parts and by Rarum the contrary As when we say a Town is thick with houses or a Wood with trees we mean not that one house or tree is thicker than another but that the spaces between are not so great But since there is no Vacuum the spaces between the parts of Air are no larger than between the parts of Water or of any thing else A. What think you of those things which Mariners that have sailed through the Atlantick Sea called Spouts which pour down water enough at once to drown a great Ship B. 'T is a thing I have not seen And therefore can say nothing to it though I doubt not but when two very large and heavie Clouds shall be driven together by two great and contrary winds the thing is possible A. I think your reason good And now will propound to you another Experiment I have seen an exceeding small Tube of Glass with both ends open set upright in a Vessel of Water and that the Superficies of the Water within the Tube was higher a good deal than of that in the Vessel but I see no reason for it B. Was not part of the Glass under Water Must not then the Water in the Vessel rise Must not the Air that lay upon it rise with it Whither should this rising Air go since there is no place empty to receive it It is therefore no wonder if the Water press'd by the Substance of the Glass which is dipt into it do rather rise into a very small Pipe than come about a longer way into the open Air. A. 'T is very probable I observed also that the top of the inclosed Water was a concave Superficies which I never saw in other Fluids B. The Water hath some degree of tenacity though not so great but that it will yield a little to the Motion of the Air as is manifest in the Bubbles of water where the concavity is always towards the Air. And this I think the cause why the Air and Water meeting in the Tube make the Superficies towards the Air concave which it cannot do to a Fluid of greater tenacity A. If you put into a Bason of Water a long rag of Cloth first drenched in water and let the longer part of it hang out it is known by Experience that the Water will drop out as long as there is any part of the other end under Water B. The cause of it is that water as I told you hath a degree of tenacity And therefore being continued in the rag till it be lower without than within the weight will make it continue dropping though not onely because it is heavie for if the rag lay higher without than within and were made heavier by the breadth it would not descend but 't is because all heavie Bodies Naturally descend with proportion of swiftness duplicate to that of the time whereof I shall say more when we talk of Gravity A. You see how despicable Experiments I trouble you with But I hope you will pardon me B. As for mean and common Experiments I think them a great deal better Witnesses of Nature than those that are forced by fire and known but to very few CAP. VI. Of the Causes and Effects of Heat and Cold. A. 'T Is a fine day and pleasant walking through the Fields but that the Sun is a little too hot B. How know you that the Sun is hot A. I feel it B. That is to say you know that your self but not that the Sun is hot But when you finde your self hot what Body do you feel A. None B. How then can you infer your heat from the Sense of Feeling Your walking
may have made you hot Is Motion therefore hot No. You are to consider the Concomitants of your heat as that you are more faint or more ruddy or that you sweat or feel some Endeavour of Moisture or Spirits tending outward and when you have found the Causes of those Accidents you have found the Causes of Heat which in a living Creature and specially in a Man is many times the Motion of the parts within him such as happen in sickness anger and other passions of the minde which are not in the Sun nor in Fire A. That which I desire now to know is what Motions and of what Bodies without me are the Efficient Causes of my Heat B. I shewed you yesterday in discoursing of Rain how by this compounded Motion of the Suns Body the Air was every way at once thrust off West and East so that where it was contiguous the small parts of the water were forced to rise for the avoiding of Vacuum Think then that your hand were in the place of water so exposed to the Sun Must not the Sun work upon it as it did upon the Water Though it break not the skin yet it will give to the inner Fluids and looser parts of your hand an Endeavour to get forth which will extend the skin and in some climates fetch up the bloud and in time make the skin black The Fire also will do the same to them that often sit with their naked skins too neer it Nay one may sit so neer without touching it as it shall blister or break the skin and fetch up both spirits and bloud mixt into a putrid oyly matter sooner than in a Furnace Oyl can be extracted out of a Plant. A. But if the Water be above the Fire in a Kettle what then will it do Shall the particles of water go toward the Fire as it did toward the Sun B. No. For it cannot But the Motion of the parts of the Kettle which are caused by the Fire shall dissipate the Water into Vapour till it be all cast out A. What is that you call Fire Is it a hard or Fluid Body B. It is not any other Body but that of the shining coal which coal though extinguished with Water is still the same Body So also in a very hot Furnace the hollow spaces between the shining coals though they burn that you put into them are no other Body than Air moved A. Is it not Flame B. No. For flame is nothing but a multitude of Sparks and Sparks are but the Atomes of the Fewel dissipated by the incredible swift Motion of the Movent which makes every Spark to seem a hundred times greater than it is as appears by this That when a man swings in the Air a small stick fired at one end though the Motion cannot be very swift yet the Fire will appear to the eye to be a long streight or crooked Line Therefore a great many sparks together flying upward must needs appear unto the sight as one continued Flame Nor are the sparks striken out of a Flint any thing else but small particles of the stone which by their swift Motion are made to shine But that Fire is not a substance of it self is evident enough by this that the Sun-beams passing through a Globe of Water will burn as other fire does Which beams if they were indeed Fire would be quenched in the passage A. This is so evident that I wonder so wise men as Aristotle and his followers for so long a time could hold it for an Element and one of the primary parts of the Universe But the Natural heat of a man or other living Creature whence proceedeth it Is there any thing within their Bodies that hath this compounded Motion B. At the breaking up of a Deer I have seen it plainly in his Bowels as long as they were warm And it is called the Peristaltique Motion and in the Heart of a Beast newly taken out of his Body and this Motion is called Systole and Diastole But they are both of them this compounded Motion whereof the former causeth the food to Winde up and down through the guts and the later makes the Circulation of the Blood A. What kind of Motion is the Cause of Cold Methinks it should be contrary to that which causeth Heat B. So it is in some respect For seeing the Motion that begets Heat tendeth to the separation of the parts of the Body whereon it acteth it stands with reason that the Motion which maketh Cold should be such as sets them closer together But contrary Motions are to speak properly when upon two ends of a Line two Bodies move towards each other the Effect whereof is to make them meet But each of them as to this Question is the same A. Do you think as many Philosophers have held and now hold that Cold is nothing but a privation of Heat B. No. Have you never heard the Fable of the Satyre that dwelling with a Husbandman and seeing him blow his fingers to warm them and his Pottage to cool it was so scandalized that he ran from him saying he would no longer dwell with one that could blow both Hot and Cold with one breath Yet the Cause is evident enough For the Air which had gotten a Calefactive power from his vital parts was from his mouth and throat gently diffused on his fingers and retained still that power But to cool his Pottage he streightened the passage at his lips which extinguished the Calefactive Motion A. Do you think Wind the general Cause of Cold If that were true in the greatest Winds we should have the greatest Frosts B. I mean not any of those uncertain Winds which I said were made by the Clouds but such as a Body moved in the Air makes to and against it self For it is all one Motion of the Air whether it be carried against the Body or the Body against it Such a Wind as is constant if no other be stirring from East to West made by the Earth turning dayly upon its own Centre Which is so swift as except it be kept off by some hill to kill a man as by Experience hath been found by those who have passed over great Mountains and specially over the Andies which are opposed to the East And such is the Wind which the Earth maketh in the Air by her Annual Motion which is so swift as that by the Calculation of Astronomers to go Sixty miles in a minute of an hour And therefore this must be the Motion which makes it so cold about the Poles of the Ecliptique A. Does not the Earth make the Wind as great in one part of the Ecliptique as in another B. Yes But when the Sun is in Cancer it tempers the Cold and still less and less but least of all in the Winter-Solstice where his beams are most oblique to the Superficies of the Earth A. I thought the greatest Cold had been about the Poles of the
Aequator B. And so did I once But the reason commonly given for it is so improbable that I do not think so now For the Cause they render of it is onely that the Motion of the Earth is swiftest in the Aequinoctial and slowest about the Poles and consequently since Motion is the Cause of Heat and Cold is but as 't was thought a want of the same they inferr'd that the greatest Cold must be about the Poles of the Aequinoctial Wherein they miscounted For not every Motion causeth Heat but this agitation onely which we call compounded Motion though some have alleadged Experience for that opinion as that a Bullet out of a Gun will with its own swiftness melt Which I never shall believe A. 'T is a common thing with many Philosophers to maintain their Fancies with any rash report and sometimes with a Lye But how is it possible that so soft a Substance as water should be turned into so hard a Substance as Ice B. When the Air shaves the Globe of the Earth with such swiftness as that of Sixty miles in a minute of an hour it cannot where it meets with still water but beat it up into small and undistinguishable bubbles and involve it self in them as in so many bladders or skins of Water And Ice is nothing else but the smallest imaginable parts of Air and Water mixt which is made hard by this compounded Motion that keeps the parts so close together as not to be separated in one place without disordering the Motion of them all For when a Body will not easily yield to the impression of an external Movent in one place without yielding in all we call it Hard And when it does we say 't is Soft A. Why is not Ice as well made in a moved as in a still water Are there not great Seas of Ice in the Northern parts of the Earth B. Yes and perhaps also in the Southern parts But I cannot imagine how Ice can be made in such agitation as is always in the open Sea made by the Tides and by the Winds But how it may be made at the Shoar it is not hard to imagine For in a River or Current though swift the water that adhereth to the banks is quiet and easily by the Motion of the Air driven into small insensible bubbles and so may the water that adhereth to those bubbles and so forwards till it come into a stream that breaks it and then it is no wonder though the fragments be driven into the open Sea and freeze together into greater lumps But when in the open Sea or at the Shoar the Tide or a great Wave shall arise this young and tender Ice will presently be washt away And therefore I think it evident that as in the Thames the Ice is first made at the banks where the Tide is weak or none and broken by the stream comes down to London and part goes to the Sea floating till it dissolve and part being too great to pass the Bridge stoppeth there and sustains that which follows till the River be quite frozen over So also the Ice in the Northern Seas begins first at the banks of the Continent and Islands which are scituated in that Climate and then broken off are carried up and down and one against another till they become great Bodies A. But what if there be Islands and narrow Inlets of the Sea or Rivers also about the Pole of the Aequinoctial B. If there be 't is very likely the Sea may also there be covered all over with Ice But for the truth of this we must stay for some further discovery A. When the Ice is once made and hard what dissolves it B. The Principal Cause of it is the weight of the water it self but not without some abatement in the Stream of the Air that hardned it as when the Sun-beams are less oblique to the Earth or some contrary Wind resisteth the stream of the Air. For when the impediment is removed then the nature of the water only worketh and being a heavie Body downward A. I forgot to ask you Why two pieces of Wood rub'd swiftly one against another will at length set on fire B. Not onely at length but quickly if the Wood be dry And the Cause is evident viz. the compounded Motion which dissipates the external small parts of the Wood. And then the inner parts must of necessity to preserve the Plenitude of the Universe come after first the most Fluid and then those also of greater consistence which are first erected and the Motion continued made to flie swiftly out whereby the Air driven to the Eye of the beholder maketh that fancie which is called Light A. Yes I remember you told me before that upon any strong pressure of the Eye the resistance from within would appear a Light But to return to the enquiry of Heat and Cold there be two things that beyond all other put me into admiration One is the swiftness of kindling in Gunpowder The other is the freezing of Water in a Vessel though not far from the fire set about with other water with Ice and Snow in it When Paper or Flax is flaming the flame creeps gently on and if a house full of Paper were to be burnt with putting a Candle to it it will be long in burning whereas a spark of fire would set on flame a mountain of Gunpowder in almost an instant B. Know you not Gunpowder is made of the powder of Charcole Brimstone and Salt-peter Whereof the first will kindle with a spark the second flame as soon as toucht with fire and the third blows it as being composed of many Orbs of Salt fill'd with Air and as it dissolveth in the flame furiously blowing increaseth it And as for making Ice by the fire side It is manifest that whilst the Snow is dissolving in the external vessel the Air must in the like manner break forth and shave the Superficies of the inner vessel and work through the water till it be frozen A. I could easily assent to this if I could conceive how the Air that shaves as you say the outside of the Vessel could work through it I conceive well enough a pail of water with Ice or Snow dissolving in it and how it causeth Wind. But how that Wind should communicate it self through the vessel of wood or metal so as to make it shave the Superficies of the water which is within it I do not so well understand B. I do not say the inner Superficies of the vessel shaves the water within it But 't is manifest that the Wind made in the Pail of water by the melting Snow or Ice presseth the sides of the Vessel that standeth in it and that the pressure worketh clean through how hard soever the Vessel be and that again worketh on the water within by restitution of its parts and so hardeneth the water by degrees A. I understand you now The Ice in the Pail
is that which maketh Fermentation scattering dissimilar parts and congregating similar A. Why do some hard Bodies resist breaking more one way than another B. The Bodies that do so are for the most part Wood and receive that quality from their generation For the heat of the Sun in the Spring-time draweth up the moisture at the Root and together with it the small parts of the Earth and twisteth it into a small twig by its Motion upwards to some length but to very little other dimensions and so leaves it to dry till the Spring following and then does the same to that and to every small part round about it so that upward the strength is doubled and the next year trebled c. And these are called the grain of the Wood and but touch one another like sticks with little or no binding and therefore can hardly be broken across the grain but easily all-along it Also some other hard Bodies have this quality of being more fragile one way than another as we see in quarrels of a Glass-window that are aptest many times to break in some crooked Line The cause of this may be that when the glass hot from the Furnace is poured out upon a Plain any small stones in or under it will break the stream of it into divers lines and not onely weaken it but also cause it falsly to represent the Object you look on through it A. What is the Cause why a Bow of Wood or Steel or other very hard Body being bent but not broken will recover its former degree of straightness B. I have told you already how the smallest parts of a hard Body have every one by the generation of hardness a Circular or other compounded Motion such Motion is that of the smallest parts of the Bow Which Circles in the bending you press into narrower figures as a Circle into an Ellipsis and an Ellipsis into a narrower but longer Ellipsis with violence which turns their Natural Motion against the outward parts of the Bow so bent and is an Endeavour to stretch the Bow into its former posture Therefore if the impediment be removed the Bow must needs recover its former Figure A. 'T is manifest and the cause can be no other but that except the Bow have Sense B. And though the Bow had Sense and Appetite to boot the Cause will be still the same A. Do you think Air and Water to be pure and Homogeneous Bodies B. Yes and many Bodies both Hard and Heavie to be so too and many liquors also besides water A. Why then do men say they finde one Air healthy another infectious B. Not because the nature of the Air varies but because there are in the Air drawn or rather beaten up by the Sun many little Bodies whereof some have such Motion as is healthful others such as is hurtful to the life of man For the Sun as you see in the generation of Plants can fetch up Earth as well as Water and from the driest ground any kind of Body that lieth loose so it be small enough rather than admit any Emptiness By some of these small Bodies it is that we live which being taken in with our breath pass into our blood and cause it by their compounded Motion to circulate through the Veins and Arteries which the blood of it self being a heavie Body without it cannot do What kind of substance these Atomes are I cannot tell Some suppose them to be Nitre As for those infectious creatures in the Air whereof so many die of the Plague I have heard that Monsieur Des Cartes a very ingenious man was of opinion that they were little Flies But what grounds he had for it I know not though there be many Experiments that invite me to believe it For first we know that the Air is never universally infected over a whole Country but onely in or neer to some populous Town And therefore the cause must also be partly ascribed to the multitude thronged together and constrained to carry their Excrements into the fields round about and neer to their habitation Which in time fermenting breed Worms which commonly in a month or little more naturally become Flies and though engendred at one Town may flie to another Secondly in the beginning of a Plague those that dwell in the Suburbs that is to say neerest to this corruption are the poorest of the people that are nourished for the most part with the Roots and Herbs which grow in that corrupted dirt so that the same filth makes both the blood of poor people and the substance of the Fly And 't is said by Aristotle that every thing is nourished by the matter whereof it is generated Thirdly when a Town is infected the Gentlemen and those that live on wholsomest food scarce one of Five hundred die of the Plague It seems therefore whatsoever creatures they be that invade us from the Air they can discern their proper nourishment and do not enter into the mouth and nostrils with the breath of every man alike as they would do if they were inanimate Fourthly a man may carry the infection with him a great way into the Country in his Clothes and infect a Village Shall another man there draw the Infection from the Clothes onely by his breath Or from the Hangings of a Chamber wherein a man hath died It is impossible Therefore whatsoever killing thing is in the Clothes or Hangings it must rise and go into his mouth or nostrils before it can do him hurt It must therefore be a Fly whereof great numbers get into the blood and there feeding and breeding Worms obstruct the Circulation of the blood and kill the man A. I would we knew the palate of those little Animals we might perhaps finde some medicine to fright them from mingling with our breath But what is that which kills men that lie asleep too neer a Charcole-fire Is it another kind of Fly Or is Charcole venimous B. It is neither Fly nor venim but the Effect of a flameless glowing fire which dissipates those Atomes that maintain the circulation of the blood so that for want of it by degrees they faint and being asleep cannot remove but in short time there sleeping die as is evident by this that being brought into the open Air without other help they recover A. 'T is very likely The next thing I would be informed of is the nature of Gravity But for that if you please we will take another day CAP. VIII Of Gravity and Gravitation B. WHat Books are those A. Two Books written by two learned men concerning Gravity I brought them with me because they furnish me with some material Questions about that Doctrine though of the nature of Gravity I finde no more in either of them than this That Gravity is an Intrinsecal Quality by which a Body so qualified descendeth perpendicularly towards the Superficies of the Earth B. Did neither of them consider that descending is local Motion
first Endeavour of the Movent which Endeavour how weak soever is also Motion For if it have no Effect at all neither will it do any thing though doubled trebled or by what number soever multiplied For Nothing though multiplied is still Nothing Other Axiomes and Definitions we will take in as we need them by the way A. Is this all the preparation I am to make B. No you are to consider also the several kinds and properties of Motion viz. when a Body being moved by one or more Movents at once in what way it is carried straight circular or otherwise crooked and what degree of swiftness as also the action of the Movent whether Trusion Vection Percussion Reflexion or Refraction and further you must furnish your self with as many experiments which they call Phaenomenon as you can And supposing some Motion for the Cause of your Phaenomenon try if by evident Consequence without contradiction to any other manifest truth or experiment you can derive the Cause you seek for from your Supposition If you can 't is all that is expected as to that one Question from Philosophy For there is no Effect in Nature which the Author of Nature cannot bring to pass by more ways than one A. What I want of Experiments you may supply out of your own store or such Natural History as you know to be true though I can be well content with the knowledge of the Causes of those things which every Body sees commonly produced Let us therefore now enquire the Cause of some Effect particular B. We will begin with that which is the most universal the Universe and enquire in the first place if any place be absolutely empty that is to say in the language of Philosophers whether there be any Vacuum in Nature CAP. III. Of Vacuum A. 'T Is hard to suppose and harder to believe that the Infinite and Omnipotent Creator of all things should make a work so vast as is the world we see and leave a few little spaces with nothing at all in them which put altogether in respect of the whole Creature would be insensible B. Why say you that Do you think any Argument can be drawn from it to prove there is Vacuum A. Why not For in so great an Agitation of Natural Bodies may not some small parts of them be cast out and leave the places empty from whence they were thrown B. Because he that created them is not a Fancy but the most real substance that is who being Infinite there can be no place empty where he is nor full where he is not A. 'T is hard to answer this Argument because I do not remember that there is any Argument for the maintenance of Vacuum in the writings of Divines Therefore I will quit that Argument and come to another If you take a Glass Vial with a narrow neck and having suckt it dip it presently at the neck into a bason of water you shall manifestly see the water rise into the Vial. Is not this a certain signe that you had suckt out some of the Air and consequently that some part of the Vial was left empty B. No For when I am about to suck and have Air in my mouth contracting my Cheeks I drive the same against the Air in the Glass and thereby against every part of the sides of the hard Glass And this gives to the Air within an Endeavour outward by which if it be presently dipt into the water it will penetrate and enter into it For Air if it be prest will enter into any Fluid much more into water Therefore there shall rise into the Vial so much water as there was Air forced into the Bason A. This I confess is possible and not improbable B. If sucking would make Vacuum what would become of those women that are Nurses Should they not be in a very few days exhausted were it not that either the Air which is in the Childs mouth penetrateth the Milk as it descends and passeth through it or the Breast is contracted A. From what Experiment can you evidently infer that there is no Vacuum B. From many and such as to almost all men are known and familiar If two hard Bodies flat and smooth be joyned together in a common Superficies parallel to the Horizontal Plain you cannot without great force pull them asunder if you apply your force perpendicularly to the common Superficies But if you place that common Superficies erect to the Horizon they will fall asunder with their own weight From whence I argue thus Since their Contiguity in what posture soever is the same and that they cannot be pull'd asunder by a perpendicular force without letting in the ambient Air in an instant which is impossible or almost in an instant which is difficult and on the other side when the common Superficies is erect the weight of the same hard Bodies are able to break the Contiguity and let in the Air successively it is manifest that the difficulty of Separation proceeds from this that neither Air nor any other Body can be moved to any how small soever distance in an instant but may easily be moved the hardness at the sides once mastered successively So that the Cause of this difficulty of Separation is this that they cannot be parted except the Air or other matter can enter and fill the space made by their diremption And if they were infinitely hard not at all And hence also you may understand the Cause why any hard Body when it is suddenly broken is heard to crack which is the swift Motion of the Air to fill the space between Another Experiment and commonly known is of a Barrel of Liquor whose Tap-hole is very little and the Bung so stopt as to admit no Air for then the Liquor will not run but if the Tap-hole be large it will because the Air prest by a heavier Bodie will pierce through it into the Barrel The like reason holds of a Gardeners Watering-pot when the holes in the bottom are not too great A third Experiment is this Turn a thin Brass kettle the bottom upwards and lay it flat upon the Water It will sink till the water rise within to a certain height but no higher Yet let the bottom be perforated and the Kettle will be full and sink and the Air rise again through the water without But if a Bell were so laid on it would be fill'd and sink though it were not perforated because the weight is greater than the weight of the same bulk of water A. By these Experiments without any more I am convinced that there is not actually in Nature any Vacuum but I am not sure but that there may be made some little place empty and this from two Experiments one whereof is Torricellius his Experiment which is this Take a Cylinder of Glass hollow throughout but close at the end in form of a Sack B. How long A. As long as you will so it be
more than 29 inches B. And how broad A. As broad as you will so it be broad enough to pour into it Quicksilver And fill it with Quicksilver and stop up the Entrance with your finger so as to unstop it again at your pleasure Then set down a Bason or if you will a Sea of Quicksilver and inverting the Cylinder full as it is dip the end into the Quicksilver and remove your finger that the Cylinder may empt it self Do you conceive me For there is so many passing by that I cannot paint it B. Yes I conceive you well enough What follows A. The Quicksilver will descend in the Cylinder not till it be level with that in the Bason according to the nature of heavie Fluids but stay and stand above it at the height of 29 inches or very neer it the bottom being now uppermost that no Air can get in B. What do you infer from this A. That all the Cavitie above 29 inches is fill'd with Vacuum B. 'T is very strange that I from this same Experiment should infer and I think evidently that it is fill'd with Air. I pray tell me when you had inverted the Cylinder full as it was and stopt with your finger dipt into the Bason if you had then removed your finger whether you think the Quicksilver would not all have fallen out A. No sure The Air would have been prest upward through the Quicksilver it self For a man with his hand can easily thrust a Bladder of Air to the bottom of a Bason of Quicksilver B. It is therefore manifest that Quicksilver can press the Air through the same Quicksilver A. 'T is manifest and also it self rise into the Air. B. What cause then can there be why it should stand still at 29 inches above the level of the Bason rather than any place else A. 'T is not hard to assigne the cause of that For so much Quicksilver as was above the 29 inches will raise the first level of that in the bason as much as if you had pour'd it on and thereby bring it to an Aequilibrium So that I see plainly now that there is no necessity of Vacuum from this Experiment For I considered onely that naturally Quicksilver cannot ascend in Air nor Air descend in Quicksilver though by force it may B. Nor do I think that Torricellius or any other Vacuist thought of it more than you But what is the second Experiment A. There is a Sphere of Glass which they call a Recipient of the Capacity of three or four Gallons And there is inserted into it the end of a hollow Cylinder of Brass above a foot long so that the whole is one Vessel and the bore of the Cylinder three inches Diameter Into which is thrust by force a solid Cylinder of Wood covered with leather so just as it may in every point exactly touch the Concave Superficies of the Brass There is also to let out the Air which the wooden Cylinder as it enters called the Sucker drives before it a Flap to keep out the External Air while they are pulling the Sucker Besides at the top of the Recipient there is a hole to put into it any thing for Experiment The Sucker being now forc'd up into the Cylinder what do you think must follow B. I think it will require as much strength to pull it back as it did to force it in A. That is not it I ask but what would happen to the Recipient B. I think so much Air as would fill the place the Sucker leaves would descend into it out of the Recipient and also that just so much from the External Air would enter into the Recipient between the Brass and the Wood at first very swiftly but as the place increased more leasurely A. Why may not so much Air rather descend into the place forsaken and leave as much Vacuum as that comes to in the Recipient For otherwise no Air will be pumpt out nor can that wooden Pestle be called a Sucker B. That 's it I say There is no Air either pumpt or sucked out A. How can the Air pass between the Leather and the Brass or between the Leather and the Wood being so exactly contiguous or through the Leather it self B. I conceive no such exact contiguity nor such fastness of the Leather For I never yet had any that in a storm would keep out either Air or Water A. But how then could there be made in the Recipient such strange alteration both on animate and inanimate Bodies B. I will tell you how The Air descends out of the Recipient because the Air which the Sucker removeth from behinde it self as it is pulling out has no place to retire into without And therefore is driven into the Engine between the wood of the Sucker and the brass of the Cylinder and causes as much Air to come into the place forsaken by the retiring Sucker which causeth by oft repetition of the force a violent circulation of the Air within the Recipient which is able quickly to kill any thing that lives by respiration and make all the alterations that have appeared in the Engine CAP. IV. Of the Systeme of the World B. YOu are come in good time let us therefore sit down There is Ink Paper Ruler and Compass Draw a little Circle to represent the Body of the Sun A. 'T is done The Centre is A the Circumference is L M. B. Upon the same Centre A draw a larger Circle to stand for the Ecliptick For you know the Sun is always in the Plain of the Ecliptick A. There ' t is The Diameters of it at right Angles are B Z. B. Draw the Diameter of the Aequator A. How B. Through the Centre A for the Earth is also always in the Plain of the Aequator or of some of its Parallels so as to be distant from B 23 deg and a half A. Let it be H I And let C G be equal to B H and so G will be one of the Poles of the Ecliptick suppose the North-Pole and then H will be East and I West And C A produced to the Circumference in E makes E the South-Pole B. Take C K equal to C G and the Chord G K will be the Diameter of the Arctick-Circle and parallel to H I the Diameter of the Aequator Lastly upon the point B draw a little Circle wherein I suppose to be the Globe of the Earth A. 'T is drawn and marked with l m. And B D and K G joyned will be parallel and as H and I are East and West and so are B and D and G and K. B. True but producing Z B to the Circumference l m in b the Line B b will be in the Diameter of the Ecliptick of the Earth and B m in the Diameter of the Aequator of the Earth In like manner if you produce K G cutting the Circle whose Centre is G in d and e and make an Angle n G d equal
Motion of the Earth For whatsoever having been asunder comes together again must come contrary ways as those that follow one another go the same way though both move upon the same Line A. What Experiment have you seen to this purpose B. I have seen a drop of glass like that of the second Figure newly taken out of the furnace and hanging at the end of an Iron rod and yet Fluid and let fall into the water and hardned The Club-end of it A A coming first to the water the tail B C following it 'T is proved before that the motion that makes it is a compounded Motion and gives an Endeavour outward to every part of it and that the Motion which maketh Cold is such as shaving the Body in every point of contact and turning it gives them all an Endeavour inward Such is this Motion made by the sinking of the hot and fluid glass into the water 'T is therefore manifest that the Motion which hardneth a Soft Body must in every point of contact be in the contrary way to that which makes a hard body Soft And further that slender tail B C shall be made much more hard than common Glass For towards the upper end in C you cannot easily break it as small as it is And when you have broken it the whole Body will fall into dust as it must do seeing the bending is so difficult For all the parts are bent with such force that upon the breaking at D by their sudden restitution to their liberty they will break together And the cause why the tail B C being so slender becomes so hard is that all the Endeavour in the great part A B is propagated to the small part B C in the same manner as the force of the Sun-beams is derived almost to a point by a Burning-glass But the Cause why when it is broken in D it breaks also in so many other places is that the Endeavour in all the other parts which is called the Spring unbends it from whence a Motion is caused the contrary way and that Motion continued bends it more the other way and breaks it as a Bow over-bent is broken into shivers by a sudden breaking of the string A. I conceive now how a Body which having been Hard and softned again may be re-hardned but how a Fluid and meer Homogeneous Body as Air or Water may be so I see not yet For the hardning of water is making a hard Body of two Fluids whereof one which is the water hath some tenacity and so a man may make a Bladder hard with blowing into it B. As for meer Air which hath no Natural Motion of it self but is moved onely by other Bodies of a greater consistence I think it impossible to be hardned For the parts of it so easily change places that they can never be fixt by any Motion No more I think can Water which though somewhat less Fluid is with an insensible force very easily broken A. It is the opinion of many learned men that Ice in long time will be turned into Christal and they alleadge Experience for it For they say that Christal is found hanging on high Rocks in the Alps like Isicles on the Eaves of a house and why may not that have formerly been Ice and in many years have lost the power of being reduced B. If that were so it would still be Ice though also Christal Which cannot be because Christal is heavier than Water and therefore much heavier than Ice A. Is there then no transubstantiation of Bodies but by mixture B. Mixture is no transubstantiation A. Have you never seen a Stone that seemed to have been formerly Wood and some like Shells and some like Serpents and others like other things B. Yes I have seen such things and particularly I saw at Rome in a Stone-cutters work-house a Billet of Wood as I thought it partly covered with bark and partly with the grain bare as long as a mans Arm and as thick as the Calf of a mans Leg which handling I found extreme heavie and saw a small part of it which was polished and had a very fine Gloss and thought it a substance between Stone and Metal but neerest to Stone I have seen also a kind of Slate painted naturally with Forest-work And I have seen in the hands of a Chymist of my acquaintance at Paris a broken Glass part of a Retort in which had been the Rozin of Turpentine wherein though there were left no Rozin yet there appeared in the piece of Glass many Trees and Plants in the ground about them such as grow in Woods and better designed than they could be done by any Painter and continued so for a long time These be great wonders of Nature but I will not undertake to shew their causes But yet this is most certain that nothing can make a hard Body of a Soft but by some Motion of its parts For the parts of the Hardest Body in the world can be no closer together than to touch and so close are the parts of Air and Water and consequently they should be equally Hard if their smallest parts had not different Natural Motions Therefore if you ask me the Causes of these Effects I answer They are different Motions But if you expect from me how and by what Motions I shall fail you For there is no kind of Substance in the World now that was not at the first Creation when the Creator gave to all things what Natural and special Motion he thought good And as he made some Bodies wondrous great so he made others wondrous little For all his works are wondrous Man can but guess nor guess further than he hath knowledge of the variety of Motion I am therefore of opinion that whatsoever perfectly Homogeneous is Hard consisteth of the smallest parts or as some call them Atomes that were made Hard in the beginning and consequently by an Eternal Cause and that the hardness of the whole Body is caused onely by the contact of the parts by pressure A. What Motion is it that maketh a hard Body to melt B. The same compounded Motion that heats namely that of Fire if it be strong enough For all Motion compounded is an Endeavour to dissipate as I have said before the parts of the Body to be moved by it If therefore hardness consist onely in the pressing Contact of the least parts this Motion will make the same parts slide off from one another and the whole to take such a figure as the weight of the parts shall dispose them to as in Lead Iron Gold and other things melted with Heat But if the small parts have such figures as they cannot exactly touch but must leave spaces between them filled with Air or other Fluids then this Motion of the fire will dissipate those parts some one way some another the Hard part still hard as in the burning of Wood or Stone into Ashes or Lime For this Motion
that they might have called it an intrinsecal Motion rather than an intrinsecal quality A. Yes But not how Motion should be intrinsecal to the special individual Body moved For how should they when you are the first that ever sought the differences of Qualities in local Motion except your authority in Philosophy were greater with them than it is For 't is hard for a man to conceive except he see it how there should be Motion within a Body otherwise than as it is in living creatures B. But it may be they never sought or despaired of finding what natural Motion could make any inanimate thing tend one way rather than another A. So it seems But the first of them enquires no further than Why so much water being a heavie Body as lies perpendicularly on a Fishes back in the bottom of the Sea should not kill it The other whereof the Author is Dr. Wallis treateth universally of Gravity B. Well But what are the Questions which from these Books you intend to ask me A. The Author of the first Book tells me that Water and other Fluids are Bodies continued and act as to Gravity as a piece of Ice would do of the same Figure and quantity Is that true B. That the Universe supposing there is no place empty is one entire Body and also as he saith it is a continual Body is very true And yet the parts thereof may be contiguous without any other cohesion but Touch. And it is also true that a Vessel of Water will descend in a medium less heavie but Fluid as Ice would do A. But he means that water in a Tub would have the same Effect upon a Fish in the bottom of the Tub as so much Ice would have B. That also would be true if the water were frozen to the sides of it Otherwise the Ice if there be enough will crush the Fish to death But how applies he this to prove that the water cannot hurt a Fish in the Sea by its weight A. It plainly appears that Water does not Gravitate on any part of it self beneath it B. It appears by Experience but not by this Argument though instead of Water the Tub were fill'd with Quicksilver A. I thought so But how it comes to pass that the Fish remains uncrush'd I cannot tell B. The Endeavour of the Quicksilver downward is stopt by the resistance of the hard bottom But all Resistance is a contrary Endeavour that is an Endeavour upwards which gives the like Endeavour to the Quicksilver which is also heavie and thereby the Endeavour of the Quicksilver is diverted to the sides round-about where stopt again by the resistance of the sides it receives an Endeavour upwards which carries the Fish to the top lying all the way upon a soft bed of Quicksilver This is the true manner how the Fish is saved harmless But your Author I believe either wanted age or had too much business to study the doctrine of Motion and never considered that Resistance is not an impediment onely or privation but a contrary Motion and that when a man claps two pieces of Wax together their contrary Endeavour will turn both the pieces into one Cake of Wax A. I know not the Author but it seems he has deeplier considered this Question than other men For in the Introduction to his Book he saith That men have pre-engaged themselves to maintain certain Principles of their own invention and are therefore unwilling to receive any thing that may render their labour fruitless and That they have not strictly enough considered the several interventions that abate impede advance or direct the Gravitation of Bodies B. This is true enough and he himself is one of those men in that he considered not that Resistance is one of those interventions which abate impede and direct Gravitation But what are his Suppositions for the Question he handles A. His first is That as in a Pyramide of Brick wherein the Bricks are so joyned that the uppermost lies every where over the joynt or Cement of the two next below it you may break down a part and leave a Cavity and yet the Bricks above will stand firm and sustain one another by their cross posture So also it is in Wheat Hail-shot Sand or Water and so they arch themselves and thereby the Fish is every way secured by an arch of water over it B. That the cause why Fishes are not crusht nor hurt in the bottom of the Sea by the weight of the water is the waters arching it self is very manifest For if the uppermost Orb of the water should descend by its Gravity it would tend toward the Centre of the Earth and place it self all the way in a less and lesser Orb which is impossible For the places of the same Body are always equal But that Wheat Sand Hail-shot or loose Stones should make a firm arch is not credible A. The Author therefore it seems quits it And taketh a second Hypothesis for the true Cause though the former he saith be not useless but contributes its part to it B. I see though he depart from his Hypothesis he looks back upon it with some kindness What is his second Hypothesis A. It is That Air and Water have an Endeavour to Motion upward downward directly obliquely and every way For Air he saith will come down his chimney and in at his door and up his stairs B. Yes and mine too and so would Water if I dwelt under water rather than admit of Vacuum But what of that A. Why then it would follow that those several tendencies or Endeavours would so abate impede and correct one another as none of them should Gravitate Which being granted the Fish can take no harm Wherein I finde one difficulty Which is this The Water having an Endeavour to Motion every way at once methinks it should go no way but lie at rest which he saith was the opinion of Stevinus and rejecteth it saying it would crush the Fish into pieces B. I think the Water in this case would neither rest nor crush For the Endeavour being as he saith intrinsecal and every way must needs drive the water perpetually outward that is to say as to this Question upwards and seeing the same Endeavour in one individual Body cannot be more ways at once than one it will carry it on perpetually without limit beyond the fixed Stars and so we shall never more have rain A. As ridiculous as it is it necessarily follows B. What are Dr. Wallis his Suppositions A. He goes upon Experiments And first he alleadgeth this That Water left to it self without disturbance does naturally settle it self into a Horizontal Plain B. He does not then as your Author and all other men take Gravity for that Quality whereby a Body tendeth to the Centre of the Earth A. Yes he defines Gravity to be a Natural propension towards the Centre of the Earth B. Then he contradicteth himself For if all heavie
Bodies tend naturally to one Centre they shall never settle in a Plain but in a Spherical Superficies But against this That such an Horizontal Plain is found in water by Experience I say it is impossible For the Experiment cannot be made in a Bason but in half a mile at Sea Experience visibly shews the contrary According to this he should think also that a pair of Scales should hang parallel A. He thinks that too B. Let us then leave this Experiment What saies he further concerning Gravity A. He takes for granted not as an Experiment but an Axiome that Nature worketh not by election but ad ultimum virium with all the power it can B. I think he means for 't is a very obscure passage that every inanimate Body by nature worketh all it can without election which may be true But 't is certain that men and beasts work often by election and often without election as when he goes by election and falls without it In this sence I grant him that Nature does all it can But what infers he from it A. That naturally every Body has every way if the ways oppose not one another an Endeavour to Motion And consequently that if a Vessel have two holes one at the side another at the bottom the water will run out at both B. Does he think the Body of water that runs out at the side and that which runs out at the bottom is but one and the same Body of water A. No sure He cannot think but that they are two several parts of the whole Water in the Vessel B. What wonder is it then if two parts of water run two ways at once or a thousand parts a thousand ways Does it follow thence that one Body can go more than one way at once Why is he still medling with things of such difficulty He will finde at last that he has not a Genius either for Natural Philosophy or for Geometry What other Suppositions has he A. My first Author had affirmed that a lighter Body does not Gravitate on a heavier against this Dr. Wallis thus argueth Let there be a Siphon A B C D filled with Quicksilver to the level A D. If then you pour Oyl upon A as high as to E he asketh if the Oyl in A E as being heavie shall not press down the Quicksilver a little at A and make it rise a little at D suppose to F. And answers himself that certainly it will So that it is neither an Experiment nor an Hypothesis but onely his opinion B. Whatsoever it be it is not true though the Doctor may be pardoned because the contrary was never proved A. Can you prove the contrary B. Yes For the Endeavour of the Quicksilver both from A and D downward is stronger than that of the Oyl downward If therefore the Endeavour of the Quicksilver were not resisted by the bottom B C it would fall so by reason of the acceleration of heavie Bodies in their descending as to leave the Oyl so that it should not onely not press but also not touch the Quicksilver It is true in a pair of Scales equally charged with Quicksilver that the addition of a little Oyl to either Scale will make it praeponderate And that was it deceiv'd him A. 'T is evident The last Experiment he cites is the weighing of Air in a pair of Scales where 't is found manifestly that it has some little weight For if you weigh a Bladder and put the weight into one Scale and then blow the Bladder full of Air and put it into the other Scale the full Bladder will outweigh the empty Must not then the Air Gravitate B. It does not follow I have seen the Experiment just as you describe it but it can never be thence demonstrated that Air has any weight For as much Air as is prest downward by the weight of the blown Bladder so much will rise from below and lay it self Spherically at the altitude of the Center of gravity of the Bladder so blown So that all the Air within the Bladder above that Centre is carried thither imprisoned and by violence And the force that carries it up is equal to that which presseth it down There must therefore be allowed some little counterpoise in the other Scale to ballance it Therefore the Experiment proves nothing to his purpose And whereas they say there be small heavie Bodies in the Air which make it Gravitate do they think the force which brought them thither cannot hold them there A. I leave this Question of the Fish as cleerly resolved because the water tending every way to one point which is the Centre of the Earth must of necessity arch it self And now tell me your own opinion concerning the Cause of Gravity and why all Bodies descend or ascend not all alike For there can be no more Matter in one place than another if the places be equal B. I have already shewed you in general that the difference of Motion in the parts of several Bodies makes the difference of their Natures And all the difference of Motions consisteth either in swiftness or in the way or in the duration But to tell you in Special why Gold is heaviest and then Quicksilver and then perhaps Lead is more than I hope to know or mean to enquire for I doubt not but that the Species of heavie hard Opaque and Diaphanous were all made so at their creation and at the same time separated from different Species So that I cannot guess at any particular Motions that should constitute their natures further than I am guided by the Experiments made by fire or mixture A. You hope not then to make Gold by Art B. No unless I could make one and the same thing heavier than it was God hath from the beginning made all the Kindes of Hard and Heavie and Diaphanous Bodies that are and of such Figure and magnitude as he thought fit but how small soever they may by accretion become greater in the Mine or perhaps by generation though we know not how But that Gold by the art of man should be made of not Gold I cannot understand nor can they that pretend to shew how For the heaviest of all Bodies by what mixture soever of other Bodies will be made lighter and not to be received for Gold A. Why when the Cause of Gravity consisteth in Motion should you despair of finding it B. It is certain that when any two Bodies meet as the Earth and any heavie Body will the Motion that brings them to or towards one another must be upon two contrary ways and so also it is when two Bodies press each other in order to make them Hard. So that one contrariety of Motion might cause both Hard and Heavie But it doth not For the hardest Bodies are not always the heaviest Therefore I finde no access that way to compare the Causes of different Endeavours of heavie Bodies to descend A. But shew
me at least how any heavie Body that is once above in the Air can descend to the Earth when there is no visible movent to thrust or pull it down B. 'T is already granted that the Earth hath this compounded Motion supposed by Copernicus and that thereby it casteth the Contiguous Air from it self every way round-about Which Air so cast off must continually by its nature range it self in a Spherical Orb. Suppose a Stone for instance were taken up from the ground and held up in the Air by a mans hand what shall come into the place it fill'd when it lay upon the Earth A. So much Air as is equal to the Stone in magnitude must descend and place it self in an Orb upon the Earth But then I see that to avoid Vacuum another Orb of Air of the same magnitude must descend and place it self in that and so perpetually to the mans hand and then so much Air as would fill the place must descend in the same manner and bring the Stone down with it For the Stone having no Endeavour upward the least Motion of the Air the hand being removed will thrust it downward B. 'T is just so And further the Motion of the Stone downward shall continually be accelerated according to the odde numbers from Unity as you know hath been demonstrated by Galileo But we are nothing the nearer by this to the knowledge of why one Body should have a greater Endeavour downward than another You see the Cause of Gravity is this compounded Motion with exclusion of Vacuum A. It may be 't is the Figure that makes the difference For though Figure be not Motion yet it may facilitate Motion as you see commonly the breadth of a heavie Body retardeth the sinking of it And the cause of it is That it makes the Air have further to go laterally before it can rise from under it For suppose a Body of Quicksilver falling in the Air from a certain height must it not going as it does towards the Centre of the Earth as it draws neerer and neerer to the Earth become more and more slender in the form of a Solid Sector And if it have far to go divide it self into drops This Figure of a Solid Sector is like a Needle with the point downward and therefore I should think that facilitating the Motion of it does the same that would be done by increasing the Endeavour B. Do not you see that this way of facilitating is the same in Water and in all other Fluid heavy Bodies Besides your Argument ought to be applicable to the weighing of Bodies in a pair of Scales which it is not for there they have no such Figure it should also hold in the comparison of Gravity in Hard and Fluid Bodies A. I had not sufficiently consider'd it But supposing now as you do that both heavy and hard Bodies in their smallest parts were made so in the Creation yet because Quicksilver is harder than Water a drop of Water shall in descending be prest into a more slender Sector than a drop of Quicksilver and consequently the Earth shall more easily cast off any quantity of Water than the same quantity of Quicksilver B. This one would think were true as also that of simple Fluid Bodies those whose smallest parts naturally without the force of Fire do strongliest cohere are generally the heaviest But why then should Quicksilver be heavier than Stone or Steel Fluidity and hardness are but degrees between greater Fluidity and greater hardness Therefore to the knowledge of what it is that causeth the difference in different Bodies of their Endeavour downward there are required if it can be known at all a great many more Experiments than have been yet made It is not difficult to find why Water is heavier than Ice or other Body mix'd of Air and Water But to believe that all Bodies are heavier or lighter according to the quantity of Air within them is very hard A. I see by this that the Creator of the World as by his Power he ordered it so by his Wisdom he provided it should be never disordered Therefore leaving this Question I desire to know whether if a heavy Body were as high as a fixt Star it would return to the Earth B. 'T is hard to try But if there be this compounded Motion in the great Bodies so high such as is in the Earth it is very likely that some heavy Bodies will be carried to them But we shall never know it till we be at the like height A. What think you is the reason why a drop of Water though heavy will stand upon a Horizontal Plain of dry or unctuous Wood and not spread it self upon it For let A B in the 6th Figure be the dry Plain D the drop of Water and D C perpendicular to A B. The drop D though higher will not descend and spread it self upon it B. The reason I think is manifest For those Bodies which are made by beating of Water and Air together shew plainly that the parts of Water have a great degree of Cohesion For the skin of the Bubble is Water and yet it can keep the Air though moved from getting out Therefore the whole drop of Water at D hath a good deal of Cohesion of parts And seeing A B is an Horizontal Plain the way from the contact in D either to A or B is upwards and consequently there is no endeavour in D either of those ways but what proceeds from so much weight of Water as is able to break that Cohesion which so small a drop is too weak to do But the Cohesion being once broken as with your Finger the Water will follow A. Seeing the descent of a heavy Body increaseth according to the odd numbers 1 3 5 7 c. and the aggregates of those numbers viz. of 1 and 3 and 1 and 3 and 5 and of 1 and 3 and 5 and 7 c. are square numbers namely 4. 9. 16 the whole swiftness of the descent will be I think to the aggregate of so many swiftnesses equal to the first Endeavour as square numbers are to their sides 1 2 3 4. Is it so B. Yes you know it hath been demonstrated by Galileo A. Then if for instance you put into a pair of Scales equal quantities of Quicksilver and Water seeing they are both accelerated in the same proportion why should not the weight of Quicksilver to the weight of Water be in duplicate proportions to their first Endeavours B. Because they are in a pair Scales For there the Motion of neither of them is accelerated And therefore it will be as the first Endeavour of the Quicksilver to the first endeavour of the Water so the whole weight to the whole weight By which you may see that the Cause which takes away the Gravitation of Liquid Bodies from Fish or other lighter Bodies within them can never be derived from the weight A. I have one Question more to