Vessel if it be hollow flote upon the water being so very heavy B. Because the Vessel and the Air in it taken as one body is more easily cast off than a body of water equal to it A. How comes it to pass that a Fish especially such a broad Fish as a Turbut or a Plaice which are broad and thin in the bottom of the Sea perhaps a mile deep is not press'd to death with the weight of water that lies upon the back of it B. Because all heavy bodies descend towards one point which is the Center of the Earth and consequently the whole Sea descending at once does arch it self so as that the upper parts cannot press the parts next below them A. It is evident Nor can there be possibly any weight as some suppose there is of a Cylinder of Air or Water or of any other liquid thing while it remains in its own Element or is sustained and inclosed in a Vessel by which one part cannot press the other CHAP. II. Problems of Tides A. WHat makes the Flux and Reflux of the Sea twice in a natural day B. We must come again to our Basen of water wherein you have seen whilst it was moved how the water mounteth up by the sides and withal goes circling round about Now if you should fasten to the inside of the Basen some bar from the bottom to the top you would see the water instead of going on go back again from that bar ebbing and the water on the other side of the bar to do the same but in counter-time and consequently to be highest where the contrary streams meet together and then return again marking out four quarters of the Vessel two by their meeting which are the high waters and two by their retiring which are the low waters A. What bar is that you find in the Ocean that stops the current of the water like that you make in the Basen B. You know that the main Ocean lies East and West between India and the Coast of America and again on the other side between America and India If therefore the Earth have such a motion as I have supposed it must needs carry the current of the Sea East and West In which course the bar that stoppeth it is the South part of America which leaves no passage for the water but the narrow Streight of Magellan The Tide rises therefore upon the Coast of America And the rising of the same in this part of the world proceedeth from the swelling chiefly of the water there and partly also from the North Sea which lieth also East and West and has a passage out of the South Sea by the Streight of Anian between America and Asia A. Does not the Mediterranean-Sea lie also East and West why are there not the like Tides there B. So there are proportionable to their lengths and quantity of water A. At Genoa at Ancona there are none at all or not sensible B. At Venice there are and in the bottom of the Streights and a current all along both the Mediterranean-Sea and the Gulf of Venice And it is the current that makes the Tides unsensible at the sides but the check makes them visible at the bottom A. How comes it about that the Moon hath such a stroke in the business as so sensibly to encrease the Tides at Full and Change B. The motion I have hitherto supposed but in the Earth I suppose also in the Moon and in all those great Bodies that hang in the Air constantly I mean the Stars both fixed and errant And for the Sun and Moon I suppose the Poles of their motion to be the Poles of the Aequinoctial which supposed it will follow because the Sun the Earth and the Moon at every Full and Change are almost in one streight line that this motion of the Earth will be made swifter than in the Quarters For this motion of the Sun and Moon being communicated to the Earth that hath already the like motion maketh the same greater and much greater when they are all three in one streight line which is only at the Full and Change whose Tides are therefore called Spring Tides A. But what then is the cause that the Spring-Tides themselves are twice a year namely when the Sun is in the Equinoctial greater than at any other times B. At other times of the year the Earth being out of the Aequinoctial the motion thereof by which the Tides are made will be less augmented by so much as a motion in the obliquity of 23 degrees or thereabout which is the distance between the Aequinoctial and Ecliptick Circles is weaker then the motion which is without obliquity A. All this is reasonable enough if it be possible that such motions as you suppose in these bodies be really there But that is a thing I have some reason to doubt of For the throwing off of Air consequent to these motions is the cause 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
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
equal B. The cause can be no other The smallest spark of Fire flying up seems a line drawn upward and again by that swift circular Motion which we have supposed for the cause of Light seems also broader then it is And consequently the Flame of every thing must needs seem much greater then it is A. What are those sparks that flie out of the Fire B. They are small pieces of the wood or Coals or other Fuel loosened and carried away with the Air that cometh up with them And being extiguished before their parts be quite dissipated into others are so much Soot and black and may be fired again A. A Spark of Fire may be stricken out of a cold stone It is not therefore Heat that makes this shining B. No 'T is the Motion that makes both the Heat and shining and the stroke makes the Motion For every of those Sparks is a little parcel of the stone which swiftly moved imprinteth the same Motion into the matter prepared or 〈◊〉 receive it A. How comes the Light of the Sun to burn almost any combustible matter by rerefraction through a convex glass and by reflection from a concave B. The Air moved by the Sun presseth the convex glass in such manner as the action continued through it proceedeth not in the same streight line by which it proceeded from the Sun but tendeth more toward the center of the body it enters Also when the action is continued through the convex body it bendeth again the same way By which means the whole action of the Sun-beams are enclosed within a very small compass in which place therefore there must be a very vehement Motion and consequently if there be in that place combustible matter such as is not very hard kindle the parts of it will be dissipated and receive that Motion which worketh on the Eye as other Fire does The same reason is to be given for burning by Reflection For there also the Beams are collected into almost a point A. Why may not the Sun-beams be such a Body as we call Fire and pass through the pores of the glass so disposed as to cary them to a point or very near B. Can there be a glass that is all pores If there cannot then cannot this effect be produced by the passing of Fire through the pores You have seen men llght their Tobacco at the Sun with a burning glass or with a ball of Cristal held which way they will indifferently Which must be impossible unless the ball were all pores Again neither you nor I can conceive any other Fire then we have seen nor then such as water will put out But not only a solid Globe of Glass or Cristal will serve for a burning Glass but also a hollow one filled with water How then does the Fire from the Sun pass through the glass of water without being put out before it come to the matter they would have it burn A. I know not There comes nothing from the Sun If there did there is come so much from it already that at this day we had had no Sun CHAP. V. Problems of Hard and Soft A. WHat call you Hard and what Soft B. That body whereof no one part is easily put out of its place without removing the whole is that which I and all men call Hard and the contrary Soft So that they are but degrees one of another A. What is the cause that makes one body Harder then another or seeing you say they are but degrees of one another what makes one body Softer then another and the same body sometimes Harder sometimes Softer B. The same Motion which we have supposed from the beginning for the cause of so many other effects Which Motion not being upon the center of the part moved but the part it self going in another circle to and again it is not necessary that the Motion be perfectly circular For it is not circulation but the reciprocation I mean the to and again that does cast off and lacerrate the Air and consequently produce the fore-mentioned effects For the cause therefore of Hardness I suppose the reciprocation of Motion in those things which are Hard to be very swift and in very small circles A. This is somewhat hard to believe I would you could supply it with some visible experience B. When you see for example a Cross-bow bent do you think the parts of it stir A. No. I am sure they do not B. How are you sure You have no argument for it but that you do not see the Motion When I see you sitting still must I believe there is no Motion in your parts within when there are so many arguments to convince me there is A. What argument have you to convince me that there is Motion in a Cross-bow when it stands bent B. If you cut the string or any way set the Bow at liberty it will have then a very visible Motion What can be the cause of that A. Why the setting of the Bow at liberty B. If the Bow had been crooked before it was bent and a string tied to both ends and then cut asunder the Bow would not have stir'd Where lies the difference A. The Bow bent has a Spring unbent it has none how crooked soever B. What mean you by Spring A. An endeavour of restitution to it's former posture B. I understand Spring as well as I do endeavour A. I mean a Prnciple or beginning of Motion in a contrary way to that of the force which bent it B. But the beginning of Motion is also Motion how insensible soever it be And you know that nothing can give a beginning of Motion to it self What is it therefore that gives the Bow which you say you are sure was at rest when it stood bent its first endeavour to return to its former posture A. It was he that bent it B. That cannot be For he gave it an endeavour to come forward and the Bow endeavours to go backward A. Well grant that endeavour be Motiou and Motion in the Bow unbent how do you derive from thence that being set at liberty it must return to its former posture B. Thus There being within the Bow a swift though invisible Motion of all the parts and consequently of the whole the bending causeth that Motion which was along the Bow that was beaten out when it was hot into that length to operate a cross the length in every part of it and the more by how much it is more bent and consequently endeavours to unbend it all the while it stands bent And therefore when the force which kept it bent is removed it must of necessity return to the posture it had before A. But has that endeavour no effect at all before the impediment be removed For if endeavour be Motion and every Motion have some effect more or less methinks this endavour should in time produce something B. So it does For in time in a long time the