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 you 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
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 a year to the Aequinoctial B. From the Autumnal Aequinox the Sun goeth on toward the Southern Tropique And therefore cannot dissolve the Snow on that side of the Hills that look towards Egypt A. But then there ought to be such another Innundation Southward B. No doubt but there is a greater descent of water there in their Summer then at other times as there must be wheresoever there is much Snow melted But what should that innundate unless it should overflow the Sea that comes close to the foot of those Mountains And for the cause why it seldom Rains in Egypt it may be this That there are no very high Hills near it to collect the Clouds The Mountains whence Nile riseth being near 2000 Miles off The nearest on one side are the Mountains of Nubia and on the other side Sina and the Mountains of Arrabia A. Whence think you proceed the Winds B. From the Motion I think especially of the Clouds partly also from whatsoever is moved in the Air. A. It is manifest that the Clouds are moved by the Winds so that there were Winds before any clouds could be moved Therefore I think you make the Effect before the Cause B. If nothing could move a Cloud but Wind your objection were good But you allow a Cloud to descend by it's own weight But when it so descends it must needs move the Air before it even to the Earth and the Earth again repel it and so make lateral Winds every way Which will carry forwards other Clouds if there be any in their way but not the Cloud that made them The Vapour of the water rising into Clouds must needs also as they rise raise a Wind A. I grant it But how can the slow motion of a Cloud make so swift a Wind as it does B. It is not one or two little Clouds but many and great ones that do it Besides when the Air is driven into places already covered it cannot but be much the swifter for the narrowness of the
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 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-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 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
passage A. Why does the South Wind more often then any other bring Rain with it B. Where the Sun hath most power and where the Seas are greatest that is in the South there is most water in the Air which a South wind can only bring to us But I have seen great showers of Rain sometimes also when the wind hath been North but it was in Summer and came first I think from the South or West and was but brought back from the North. A. I have seen at Sea very great Waves when there was no Wind at all What was it then that troubled the Water B. But had you not Wind enough presently after A. We had a Storm within a little more then a quarter of an hour after B. That Storm was then coming and had moved the Water before it But the Wind you could not perceive for it came downwards with the descending of the Clouds and pressing the Water bounded above your Sail till it came very near And that was it that made you think there was no Wind at all A. How comes it to pass that a Ship should go against the Wind which moves it even almost point blank as if it were not driven but drawn B. You are to know first that what Body soever is carryed against another Body whether perpendicularly or obliquely it drives it in a perpendicular to the superficies it lighteth on As for Example a Bullet shot against a flat wall maketh the Stone or other matter it hits to retire in a perpendicular to that flat or if the Wall be round towards the center that is to say perpendicularly For if the way of the motion be oblique to the Wall the motion is compounded of two motions one parrallel to the Wall and the other perpendicular By the former whereof the Bullet is carried along the Wall side by the other it approacheth to it Now the former of these motions can have no effect upon it all the battery is from the motion perpendicular in which it approacheth And therefore the part it hits must also retire perpendicularly If it were not so a Bullet with the same swiftness would execute as much obliquely shot as perpendicularly which you know it does not A. How do you apply this to a Ship B. Let A. B. be the Ship the head of it A. If the Wind blow just from A. towards B. 't is true the Ship cannot go forward howsoever the sail be set Let C. D. be perpendicular to the Ship and let the Sail E. C. be never so little oblique to it and F. C. perpendicular to E. C. and then you see the Ship will gain the space D. F. to the headward A. It will so but when it is very near to the Wind it will go forward very slowly and make more way with her side to the Leeward A. It will indeed go slower in the proportion of the Line A. E. to the Line C. E. But the Ship will not go so fast as you think sideward One is the force of that Wind which lights on the side of the Ship it self the other is the bellying of the Sail for the former it is not much because the Ship does not easily put from her the Water with her side and bellying of the Sail gives some little hold for the Wind to drive the Ship a stern A. For the motion sideward I agree with you but I had thought the bellying of the Sail had made the Ship go faster B. But it does not only in a fore-wind it hinders least A. By this reason a broad thin Board should make the best Sail. B. You may easily foresee the great incommodities of such a Sail. But I have seen tryed in little what such a Wind can do in such a case For I have seen a Board set upon four truckles with a staff set up in the midst of it for a Mast and another very thin and broad Board fastned to that staff in the stead of a Sail and so set as to receive the Wind very obliquely I mean so as to be within a point of the Compass directly opposite to it and so placed upon a reasonable smooth pavement where the Wind blew somewhat strongly The event was first that it stood doubting whether it should stir at all or no but that was not long and then it ran a head extream swiftly till it was overthrown by a Rub. A. Before you leave the Ship tell me how it comes about that so small a thing as a Rudder can so easily turn the greatest Ship B. 'T is not the Rudder only there must also be a stream to do it you shall never turn a Ship with a Rudder in a standing pooll nor in a natural current You must make a stream from head to stern either with Oares or with Sails when you have made such a stream the turning of the Rudder obliquely holds the Water from passing freely and the Ship or Boat cannot go on 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
the first entrance be resisted which it was not before it entred A. How then comes a Bullet when shot very Obliquely into any broad Water and having entred yet to rise again into the Air B. When a Bullet is shot very Obliquely though the Motion be never so swift yet approach downwards to the Water is very slow and when it cometh to it it casteth up much Water before it which with its weight presseth downwards again and maketh the Water to rise under the Bullet with force enough to master the weak Motion of the Bullet downwards and to make it rise in such manner as Bodies use to rise by Reflection A. By what Motion seeing you ascribe all Effects to Motion can a Load-stone draw Iron to it B. By the same Motion hitherto supposed But though all the smallest parts of the Earth have this Motion yet it is not supposed that their Motions are in equal Circles nor that they keep just time with one another nor that they have all the same Poles If they had all Bodies would draw one another alike For such an agreement of Motion of Way of Swiftness of Poles cannot be maintained without the conjunction of the Bodies themselves in the Center of their common Motion but by violence If therefore the Iron have but so much of the Nature of the Load-stone as redily to receive from it the like Motion as one String of a Lute doth from another String strained to the same Note as it is like enough it hath the Load-stone being but one kind of Iron Ore it must needs after that Motion received from it unless the greatness of the weight hinder come nearer to it because at distance their Motions will differ in time and oppose each other whereby they will be forced to a common Center If the Iron be lifted up from the Earth the Motion of the Load-stone must be stronger or the Body of it nearer to overcome the Weight and then the Iron will leap up to the Load-stone as as Swiftly as from the same distance it would fall down to the Earth but if both the Stone and the Iron be set floating upon the Water the attraction will begin to be manifest at a greater distance because the hindrance of the weight is in part removed A. But why does the Load-stone if it float on a Calm Water never fail to place it self at last in the Meridian just North and South B. Not so just in the Meridian but almost in all places with some variations But the cause I think is that the Axis of this Magnetical Motion is parallel to the Axis of the Ecliptique which is the Axis of the like Motion in the Earth and consequently that it cannot freely exercise its Natural Motion in any other Scituation A. Whence may this consent of Motion in the Load-stone and the Earth proceed Do you think as some have written that the Earth is a great Load-stone B. Dr. Gilbert that was the first that wrote any thing of this Subject rationally inclines to that opinion Decartes thought the Earth excepting this upper crust of a few Miles depth to be of the same Nature with all other Stars and bright For my part I am content to be ignorant but I believe the Load stone hath given its virtue by a long habitude in the Mine the Vein of it lying in the plain of some of the Meridians or rather of some of the great Circles that pass through the Poles of the Ecliptique which are the same with the Poles of the like Motion supposed in the Earth A. If that be true I need not ask why the filings of Iron laid on a Load-stone equally distant from its Poles will lie parallel to the Axis but one each side incline to the Pole that is next it Nor why by drawing a Load-ston all a long a Needle of Iron the Needle will receive the same Poles Nor why when the Load-stone and Iron or two Load-stones are put together floating upon Water will fall one of them a Stern of the other that their like parts may look the same way and their unlike touch in which Action they are commonly said to Repel one another For all this may be deriv'd from the union of their Motions One thing more I desire to know and that is What are those things they call Spirits I mean Ghosts Fairies Hobgoblins and the like Apparitions B. They are no part of the Subject of Natural Philosophy A. That which in all Ages and all places is commonly seen as those have been unless a great part of Mankind by Lyers cannot I think be supernatural B. All this that I have hitherto said though upon better ground than can be had for a discourse of Ghosts you ought to take but for a Dream A. I do so But there be some Dreams more like sense then others And that which is like sense pleases me as well in natural Philosophy as if it were the very truth B. I was Dreaming also once of these things but was weakened by their noise And they never came into any Dream of mine since unless Apparitionrs in Dreams and Ghoasts be all one CHAP. VIII The Delphique Problem or Duplication of the Cube A. HAve you seen a Printed Paper sent from Paris containing the Duplication of the Cube written in French B. Yes It was I that Writ it and sent it thither to be Printed on purpose to see what objections would be made to it by our Professors of Algebra here A. Then you have also seen the confutations of it by Algebra B. I have seen some of them and have one by me For there was but one that was rightly Calculated and that is it which I have kept A. Your Demonstration then is confuted though but by one B. That does not follow For though an Arithmetical Calculation be true in Numbers yet the same may be or rather must be false if the Units be not constantly the same A. Is their Calculation so inconstant or rather so foolish as you make it B. Yes For the same number is sometimes so many Lines sometimes so many Plains and sometimes so many Solids as you shall plainly see if you will take the pains to examine first a Demonstration I have to prove the said Duplication and after that the Algebrique Calculation which is pretended to confute it And not only that this one is false but also any other Arithmetical account used in Geometry unless the numbers be always so many Lines or always so many superficies or always many solids A. Let me see the Geometrical Demonstration B. There it is Read it To find a Cube double to a Cube given LEt the side of the Cube given be V D. Produce V D to A till A D be double to D V. Then make the square of A D namely A B C D. Divide A B and C D in the middle at E and F. Draw E F. Draw also A C cutting E F in I. Then in the
demonstrated to be impossible Besides you know when they have sucked out as they think all the Air from the Glass Globe they can nevertheless both see through it what is done and hear a sound from within when there is any made Which if there were no other but there are many other is argument enough that the place is still full of Air. A. What say you to the swelling of a Bladder even to bursting if it be a little blown when it is put into the Receiver for so they call the Globe of Glass B. The stream of Air that from every side meeting together and turning in an infinite number of small points do pierce the Bladder in innumerable places with great violence at once like so many invisible small wimbles especially if the Bladder be a little blown before it be put in that it may make a little resistance And when the Air has once pierced it it is easie to conceive that it must afterward by the same violent motion be extended till it break If before it break you let in fresh Air upon it the violence of the motion will thereby be tempered and the Bladder be less extended For that also they have observed Can you imagine how a Bladder should be extended and broken by being too full of Emptiness A. How come living creatures to be killed in this Receiver in so little a time as 3 or 4 minutes of an hour B. If they suck into their lungs so violent a wind thus made you must needs think it will presently stop the passage of their bloud and that is death though they may recover if taken out before they be too cold And so likewise will it put out fire but the Coals taken out whilst they are hot will revive again 'T is an ordinary thing in many Coal-pits whereof I have seen the experience that a wind proceeding from the sides of the Pit every way will extinguish any fire let down into it and kill the workmen unless they be quickly taken out A. If you put a vessel of water into the Receiver and then suck out the Air the water will boil What say you to that B. It is like enough it will dance in so great a bustling of the Air but I never heard it would be hot Nor can I imagine how Vacuum should make any thing dance I hope you are by this time satisfied that no experiment made with the Engine at Gresham Colledge is sufficient to prove that there is or that there may be Vacuum A. The World you know is finite and consequently all that infinite space without it is empty Why may not some of that Vacuum be brought in and mingled with the Air here B. I know nothing in matters without the World A. What say you to Torricellioes Experiment in Quick-silver which is this There is a Bason at A filled with Quick-silver suppose to B And CD a hollow glass pipe filled with the same Which if you stop with your finger at B and so set it upright and then if you take away your finger the Quick-silver will fall from C downwards but not to the bottom For it will stop by the way suppose at D. Is it not therefore necessary that that space between C and D be left empty Or will you say the Quick silver does not exactly touch the sides of the glass pipe B. I 'le say neither If a man thrust down into a vessel of Quick-silver a blown Bladder will not that Bladder come up to the top A. Yes certanly or a Bladder of Iron or of any thing else but Gold B. You see then that Air can pierce Quick-silver A. Yes with so much force as the weight of Quick-silver comes to B. When the Quick-silver is fallen to D there is so much the more in the bason And that takes up the place which so much Air took up before Whither can this Air go if all the World without that glass pipe B C were full There must needs be the same or as much Air come to that space which only is empty between C and D. By what force By the weight of the Quick-silver between D and B. Which Quick-silver weigheth now upward or else it could never have raised that part higher which was at first in the Bason So you see the weight of Quick-silver can press the Air through Quick-silver up into the pipe till it come to an equality of force as in D. Where the weight of the Quick-silver is equal to the force which is required in Air to go through it A. If a man suck a Vial that has nothing in it but Air and presently dip the mouth of it into water the water will ascend into the Vial. Is not that an argument that part of the Air had been sucked out and part of the room within the Vial left empty B. No. If there were empty space in the World why should not there be also some 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 not 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
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 For Example let the wall be A B a point given E a Gun C E that carries the Bullet Perpendicularly to F and another Gun D E that carries the like Bullet with the same swiftness Oblique to G In what proportion will their Forces be upon the Wall B. The force of the stroke Perpendicular from E to F will be greater then the Oblique force from E to G in the proportion of the line E G to the line E F. A. How can the difference be so much Can the Bullet lose so much of its force in the way from E to G B. No we will suppose it loseth nothing of its swiftness But the cause is That their swiftness being equal the one is longer in coming to the wall then the other in Proportion of Time as E G to E F. For though their swiftness be the same considered in themselves yet the swiftness of their approach to the wall is greater in E F then in E G in proportion of the lines themselves A. When a Bullet enters not but rebounds from the wall does it make the same Angle going off which it did falling on as the Sun-beams do B. If you measure the Angles close by the wall there difference will not be ensible otherwise it will be great enough For the Motion of the Bullet grows continually weaker But it is not so with the Sun-beams which press continually and equally A. What is the cause of Reflection When a body can go no further on it has lost its Motion Whence then comes the Motion by which it reboundeth B. This Motion of rebounding or reflecting proceedeth from the resistance There is a difference to be considered between the Reflection of Light and of a Bullet answerable to their different Motions pressing and striking For the action which makes Reflection of Light is the Pressure of the Air upon the Reflecting Body caused by the Sun or other shining body and is but a contrary endeavour as if two men should press with their breasts upon