Licenced  
May 26. 1677. Ro. L'strange.   

Decameron Physiologicum: OR, TEN DIALOGUES OF NATURAL Philosophy.  
By THOMAS HOBBES of Malmsbury.  
To which is added The Proportion of a strait Line to half the Arc of a Quadrant. By the same AUTHOR.  
LONDON: Printed by J. C. for W. Crook at the Green Dragon without Temple-Bar. 1678.   

The Contents.  

Dial. 1. OF the Original of Natural Philosophy. Pag. 1.  
2. Of the Principles and Method of Natural Philosophy. p. 14.  
3. Of Vacuum. p. 23.  
4. Of the Systeme of the World. p. 31.  
5. Of the Motions of Water and Air. p. 46.  
6. Of the Causes and, Effects of Heat and Cold. p. 58.  
7. Of Hard and Soft, and of the Atoms that fly in the Air. p. 72.  
8. Of Gravity and Gravitation. p. 84.  
9 Of the Loadstone, and its Poles; and whether they show the Longitude of Places on the Earth. p. 104.  
10. Of Transparence, Refraction, and of the Power of the Earth to produce living Creatures. p. 121.  
The Proportion of a strait Line to half the Arc of a Quadrant; by the same Author. p. 133.    

CAP. I. Of the Original of Natural Philosophy.  A. 
I Have heard exceeding highly commended a kind of thing which I do not well understand, though it be much talked of, by such as have not otherwise much to do, by the name of Philosophy. And the same again by others as much despised and derided. So that I cannot tell whether it be good or ill, nor what to make of it, though I see many other men that thrive by it.  B. 
I doubt not, but what so many do so highly praise must be very admirable, and what is derided and scorned by many, foolish and ridiculous. The honour and scorn falleth finally not upon Philosophy, but upon the Professors. Philosophy is The knowledge of Natural Causes. And there is no Knowledge but of Truth. And to know the true Causes of things, was never in contempt, but in admiration. Scorn can never fasten upon Truth. But the difference is all in the Writers and Teachers. Whereof some have neither studied, nor care for it, otherwise than as a Trade to maintain themselves or gain Preferment; and some for Fashion, and to make themselves fit for ingenious Company: and their study hath not been meditation, but acquiescence in the Authority of those Authors whom they have heard commended. And some (but few) there be, that have studied it for Curiosity, and the delight which commonly men have in the acquisition of Science, and in the mastery of difficult and subtle Doctrines. Of this last sort I count Aristotle, and a few others of the Ancients, and some few Moderns: and to these it is that properly belong the Praises which are given to Philosophy.  A. 
If I have a mind to study (for example Natural Philosophy) must I then needs read Aristotle, or some of those that now are in request?  B. 
There's no necessity of it. But if in your own meditation you light upon a difficulty, I think 'tis no loss of time, to inquire what other men say of it, but to rely only upon Reason. For though there be some few Effects of Nature (especially concerning the Heavens) whereof the Philosophers of old time have assigned very rational Causes, such as any man may acquiesce in, as of Eclipses of the Sun and Moon by long observation, and by the Calculation of their visible Motions; yet what is that to the numberless and quotidian Phaenomena of Nature? Who is there amongst them or their Successors, that has satisfied you with the Causes of Gravity, Heat, Cold, Light, Sense, Colour, Noise, Rain, Snow, Frost, Winds, Tides of the Sea, and a thousand other things which a few men's lives are too short to go through, and which you and other curious Spirits admire (as quotidian as they are) and fain would know the Causes of them, but shall not find them in the Books of Naturalists; and when you ask what are the Causes of any of them, of a Philosopher now, he will put you off with mere words; which words, examined to the bottom, signify not a jot more than I cannot tell, or Because it is: Such as are Intrinsecal quality, Occult quality, Sympathy, Antipathy, Antiperistasis, and the like. Which pass well enough with those that care not much for such wisdom, though wise enough in their own ways; but will not pass with you that ask not simply what's the Cause, but in what manner it comes about that such Effects are produced.  A. 
That's Cozening. What need had they of that? When began they thus to play the Charletants?  B. 
Need had they none. But know you not that men from their very birth, and naturally, scramble for every thing they covet, and would have all the world, if they could, to fear and obey them? If by fortune or industry one light upon a Secret in Nature, and thereby obtain the credit of an extraordinary Knowing man, should he not make use of it to his own benefit? There is scarce one of a thousand but would live upon the charges of the people as far as he dares. What poor Geometrician is there, but takes pride to be thought a Conjurer? what Mountebank would not make a living out of a false opinion that he were a great Physician? And when many of them are once engaged in the maintenance of an Error, they will join together for the saving of their Authority to decry the Truth.  A. 
I pray, tell me, if you can, how and where the study of Philosophy first began.  B. 
If we may give Credit to old Histories, the first that studied any of the Natural Sciences were the Astronomers of Aethiopia. My Author is Diodorus Siculus, accounted a very faithful Writer, who begins his History as high as is possible, and tells us that in Aethiopia were the first Astronomers; and that for their Predictions of Eclipses, and other Conjunctions and Aspects of the Planets, they obtained of their King not only Towns and Fields to a third part of the whole Land, but were also in such veneration with the People, that they were thought to have discourse with their Gods, which were the Stars; and made their Kings thereby to stand in awe of them, that they durst not either eat or drink but what and when they prescribed; no nor live, if they said the Gods commanded them to die. And thus they continued in subjection to their false Prophets, till by one of their Kings, called Ergamenes, (about the time of the Ptolemies) they were put to the Sword. But long before the time of Ergamenes, the Race of these Astrologers (for they had no Disciples but their own Children) was so numerous, that abundance of them (whether sent for or no I cannot tell) transplanted themselves into Egypt, and there also had their Cities and Lands allowed them, and were in request not only for Astronomy and Astrology, but also for Geometry. And Egypt was then as it were an University to all the world, and thither went the curious Greeks, as Pythagoras, Plato, Thales, and others, to fetch Philosophy into Greece. But long before that time, abundance of them went into Assyria, and had their Towns and Lands assigned them also there; and were by the Hebrews called Chaldies'.  A. 
Why so?  B. 
I cannot tell; but I find in Martinius Lexicon they were called Chasdim, and Chesdim, and (as he saith) from one Chesed the son of Nachor; but I find no such man as Chesed amongst the issue of Noah in the Scripture. Nor do I find that there was any certain Country called Chaldaea; though a Town where any of them inhabited were called A Town of the Chaldies'. Martinius saith further, that the same word Chasdim did signify also Demons.  A. 
By this reckoning I should conjecture they were called Chusdim, as being a Race of Ethiopians. For the Land of Chus is Aethiopia; and so the name degenerated first into Chuldim, and then into Chaldim; so that they were such another kind of people as we call Gypsies; saving that they were admired and feared for their Knavery, and the Gypsies counted Rogues.  B. 
Nay pray, except Claudius Ptolomaeus, Author of that great Work of Astronomy, the Almegest.  A. 
I grant he was excellent both in Astronomy and Geometry, and to be commended for his Almegest; but then for his Judiciar Astrology annexed to it, he is again a Gipsy. But the Greeks that traveled (you say) into Egypt, what Philosophy did they carry home?  B. 
The Mathematics and Astronomy. But for that sublunary Physic's, which is commonly called Natural Philosophy, I have not read of any Nation that studied it earlier than the Greeks, from whom it proceeded to the Romans. Yet both Greeks and Romans were more addicted to Moral than to Natural Philosophy; in which kind we have their Writings, but loosely and incoherently, written upon no other Principles than their own Passions and Presumptions, without any respect to the Laws of Commonwealth, which are the ground and measure of all true Morality. So that their Books tend rather to teach men to censure than to obey the Laws. Which has been a great hindrance to the Peace of the Western world ever since. But they that seriously applied themselves to Natural Philosophy were but few, as Plato and Aristotle, whose Works we have; and Epicurus, whose Doctrine we have in Lucretius. The Writings of Philolaus and many other curious Students being by fire or negligence now lost: though the Doctrine of Philolaus concerning the Motion of the Earth have been revived by Copernicus, and explained and confirmed by Galileo now of late.  A. 
But methinks the Natural Philosophy of Plato and Aristotle, and the rest, should have been cultivated and made to flourish by their Disciples.  B. 
Whom do you mean, the Successors of Plato, Epicurus, Aristotle, and the other first Philosophers? It may be some of them may have been learned and worthy men. But not long after, and down to the time of our Saviour and his Apostles, they were for the most part a sort of needy, ignorant, impudent cheating fellows, who by the profession of the Doctrine of those first Philosophers, got their living. For at that time, the name of Philosophy was so much in fashion and honour amongst great persons, that every rich man had a Philosopher of one Sect or another to be a Schoolmaster to his Children. And these were they that feigning Christianity, with their disputing and readiness of talking got themselves into Christian Commons, and brought so many Heresies into the Primitive Church, every one retaining still a tang of what they had been used to teach.  A. 
But those Heresies were all condemned in the first Council of Nice.  B. 
Yes. But the Arrian Heresy for a long time flourished no less than the Roman, and was upheld by divers Emperors, and never fully extinguished as long as there were Vandals in Christendom. Besides, there arose daily other Sects, opposing their Philosophy to the Doctrine of the Councils concerning the Divinity of our Saviour; as, how many Persons he was, how many Natures he had. And thus it continued till the time of Charlemagne, when he and Pope Leo the third divided the Power of the Empire into Temporal and Spiritual.  A. 
A very unequal division.  B. 
Why? Which of them think you had the greater share?  A. 
No doubt, the Emperor: For he only had the Sword.  B. 
When the Swords are in the hands of men, whether had you rather command the Men or the Swords?  A. 
I understand you. For he that hath the hands of the Men, has also the use both of their Swords and strength.  B. 
The Empire thus divided into Spiritual and Temporal, the freedom of Philosophy was to the power Spiritual very dangerous. And for that cause it behoved the Pope to get Schools set up not only for Divinity, but also for other Sciences, especially for Natural Philosophy. Which when by the power of the Emperor he had effected, out of the mixture of Aristotle's Metaphysics with the Scripture, there arose a new Science called School-Divinity; which has been the principal Learning of these Western parts from the time of Charlemagne till of very late.  A. 
But I find not in any of the Writings of the Schoolmen in what manner, from the causes they assign, the Effect is naturally and necessarily produced.  B. 
You must not wonder at that. For you inquire not so much, when you see a change of any thing, what may be said to be the cause of it, as how the same is generated; which generation is the entire progress of Nature from the efficient cause to the Effect produced. Which is always a hard Question, and for the most part impossible for a man to answer to. For the alterations of the things we perceive by our five Senses are made by the motion of Bodies (for the most part) either for distance, smallness, or transparence, invisible.  A. 
But what need had they then to assign any cause at all, seeing they could not show the Effect was to follow from it?  B. 
The Schools (as I said) were erected by the Pope and Emperor, but directed by the Pope only, to answer and confute the Heresies of the Philosophers. Would you have them then betray their Profession and Authority, that is to say, their Livelihood, by confessing their ignorance? Or rather uphold the same, by putting for causes, strange and unintelligible words; which might serve well enough not only to satisfy the people whom they relied on, but also to trouble the Philosophers themselves to find a fault in.  A. 
Seeing you say that Alteration is wrought by the Motion of Bodies, pray tell me first what I am to understand by the word Body.  B. 
It is a hard Question, though most men think they can easily answer it, as that it is whatsoever they can see, feel, or take notice of by their Senses. But if you will know indeed what is body, we must inquire first what there is that is not Body. You have seen (I suppose) the Effects of Glasses, how they multiply and magnify the Object of our sight; as when a Glass of a certain Figure will make a Counter or a Shilling seem twenty, though you be well assured there is but one. And if you set a mark upon it, you will find the mark upon them all. The Counter is certainly one of those things we call Bodies: Are not the others so too?  A. 
No, without doubt. For looking through a Glass cannot make them really more than they are.  B. 
What then be they but fancies, so many fancies of one and the same thing in several places?  A. 
'Tis manifest they are so many Idols, mere Nothings.  B. 
When you have looked upon a Star or Candle with both your eyes, but one of them a little turned awry with your finger, has not there appeared two Stars, or two Candles? And though you call it a deception of the sight, you cannot deny but there were two Images of the Object.  A. 
'Tis true, and observed by all men. And the same I say of our faces seen in Looking-glasses, and of all Dreams, and of all Apparitions of dead men's Ghosts; and wonder, since 'tis so manifest, I never thought upon't before, for it is a very happy encounter, and such as being by every body well understood, would utterly destroy both Idolatry and Superstition, and defeat abundance of Knaves that cheat and trouble the world with their devices.  B. 
But you must not hence conclude that whosoever tells his Dream, or sometimes takes his direction from it, is therefore an Idolater, or Superstitious, or a Cheater. For God doth often admonish men by Dreams of what they ought to do; yet men must be wary in this case that they trust not Dreams with the conduct of their lives further than by the Laws of their Country is allowed: For you know what God says, Deut. 13. If a Prophet or a Dreamer of Dreams give thee a sign or a wonder, and the sign come to pass, yet if he did thee serve other Gods, let him be put to death. Here by serving other Gods (since they had chosen God for their King) we are to understand revolting from their King, or disobeying of his Laws. Otherwise I see no Idolatry nor Superstition in following a Dream, as many of the patriarchs (in the Old Testament) and of the Saints (in the New Testament) did.  A. 
Yes: Their own Dreams. But when another man shall dream, or say that he has dreamed, and require me to follow that, he must pardon me if I ask him by what Authority, especially if he look I should pay him for it.  B. 
But if commanded by the Laws you live under, you ought to follow it. But when there proceed from one Sound divers Echoes, what are those Echoes? And when with fingers crossed you touch a small Bullet, and think it two; and when the same Herb or Flower smells well to one and ill to another, and the same at several times, well and ill to yourself, and the like of Tastes, what are those Echoes, Feelings, Odours, and Tastes?  A. 
'Tis manifest they are all but Fancies. But certainly when the Sun seems to my eye no bigger than a Dish, there is behind it somewhere somewhat else (I suppose a real Sun) which creates those fancies, by working (one way or other) upon my eyes, and other Organs of my Senses, to cause that diversity of Fancy.  B. 
You say right; and that is it I mean by the word Body, which briefly I define to be any thing that hath a Being in itself, without the help of Sense.  A. 
Aristotle (I think) meaneth by Body, Substance, or Subjectum, wherein Colour, Sound, and other Fancies are (as he says) inherent. For the word Essence has no affinity with Substance. And Seneca says, he understands it not. And no wonder: for Essence is no part of the Language of mankind, but a word devised by Philosophers out of the Copulation of two names, as if a man having two Hounds could make a third (if 'twere need) of ther● Couples.  B. 
'Tis just fo. For having said in themselves (for example) A Tree is a Plant, and conceiving well enough what is the signification of those Names, knew not what to make of the word Is that couples those Names; nor daring to call it a Body, they called it by a new name, (derived from the word est) Essentia, and Substantia, deceived by the Idiom of their own Language. For in many other Tongues, and namely in the Hebrew, there is no such Copulative. They thought the Names of things sufficiently connected, when they are placed in their natural consequence; and were therefore never troubled with Essences, nor other Fallacy from the Copulative Est.   

CAP. II. Of the Principles and Method of Natural Philosophy.  A. 
THis History of the old Philosophers has not put me out of love, but out of hope of Philosophy from any of their Writings. I would therefore try if I could attain any knowledge therein by my own meditation: But I know neither where to begin, nor which way to proceed.  B. 
Your desire (you say) is to know the Causes of the Effects or Phaenomena of Nature; and you confess they are Fancies, and (consequently) that they are in yourself; so that the Causes you seek for only are without you, and now you would know how those external Bodies work upon you to produce those Phaenomena. The beginning therefore of your enquiry ought to be at What it is you call a Cause, I mean an Efficient Cause: For the Philosophers make four kinds of Causes, whereof the Efficient is one. Another they call the Formal Cause, or simply the form or essence of the thing caused; as when they say, Four equal Angles and four equal Sides are the Cause of a Square Figure, or that Heaviness is the Cause that makes heavy Bodies to descend. But that's not the Cause you seek for, nor any thing but this: It descends because it descends. The third is the Material Cause, as when they say, The Walls and Roof, etc. of a house, are the cause of a House. The fourth is the Final Cause, and hath place only in Moral Philosophy.  A. 
We will think of Final Causes upon some other occasion; of Formal and Material not at all: I seek only the Efficient, and how it acteth from the beginning to the production of the Effect.  B. 
I say then, that in the first place you are to inquire diligently into the nature of Motion. For the variations of Fancies, or (which is the same thing) of the Phaenomena of Nature, have all of them one Universal Efficient Cause, namely the variety of Motion. For if all things in the world were absolutely at rest, there could be no variety of Fancy, but living Creatures would be without sense of all Objects, which is little less than to be dead.  A. 
What if a Child new taken from the Womb should with open eyes be exposed to the Azure-Sky, do not you think it would have some sense of the Light, but that all would seem unto him Darkness?  B. 
Truly, if he had no memory of any thing formerly seen, or by any other sense perceived (which is my supposition) I think he would be in the dark. For Darkness is Darkness, whether it be black or blue, to him that cannot distinguish.  A. 
Howsoever that be, it is evident enough that whatsoever worketh is moved: for Action is Motion.  B. 
Having well considered the nature of Motion, you must thence take your Principles for the foundation and beginning of your Enquiry.  A. 
As how?  B. 
Explain as fully and as briefly as you can what you constantly mean by Motion; which will save yourself as well as others from being seduced by Aequivocation.  A. 
Then I say, Motion is nothing but change of place: For all the Effect of a Body upon the Organs of our Senses is nothing but Fancy. Therefore we can fancy nothing from seeing it moved, but change of place.  B. 
'Tis right. But you must then tell me also what you understand by Place: For all men are not yet agreed on that.  A. 
Well then; seeing we fancy a Body, we cannot but fancy it somewhere. And therefore I think Place is the fancy of Here or There.  B. 
That is not enough. Here and There are not understood by any but yourself, except you point towards it. But pointing is no part of a Definition. Besides, though it help him to find the Place, it will never bring him to it.  A. 
But seeing Sense is Fancy, when we fancy a Body, we fancy also the Figure of it, and the space it fills up. And then I may define Place to be The precise space within which the Body is contained. For Space is also part of the Image we have of the Object seen.  B. 
And how define you Time?  A. 
As Place is to a Body, so (I think) is Time to the Motion of it; and consequently I take Time to be our fancy or Image of the Motion. But is there any necessity of so much niceness?  B. 
Yes. The want of it is the greatest, if not the only cause, of all the discord amongst Philosophers, as may easily be perceived by their abusing and confounding the names of things that differ in their nature; as you shall see when there is occasion to recite some of the Tenets of divers Philosophers.  A. 
I will avoid Aequivocation as much as I can. And for the nature of Motion, I suppose I understand it by the Definition. What is next to be done?  B. 
You are to draw from these Definitions, and from whatsoever Truth else you know by the light of Nature, such general Consequences as may serve for Axioms, or Principles of your Ratiocination.  A. 
That is hard to do.  B. 
I will draw them myself, as many as for our present discourse of Natural Causes we shall have need of; so that your part will be no more than to take heed I do not deceive you.  A. 
I will look to that.  B. 
My first Axiom than shall be this: Two Bodies, at the same Time, cannot be in one Place.  A. 
That's true: For we number Bodies as we fancy them distinct, and distinguish them by their Places. You may therefore add, Nor one Body at the same time in two Places. And Philosophers mean the same, when they say, There is no penetration of Bodies.  B. 
But they understand not their own words: For penetration signifies it not.  
My second Axiom is, That nothing can begin, change, or put an end to its own Motion. For supposing it begin just now, or being now in Motion, change its Way or Stop; I require the Cause why now rather than before or after, having all that is necessary to such Motion, Change, or Rest, alike at all times.  A. 
I do not doubt but the Argument is good in Bodies inanimate; but perhaps in Voluntary Agents it does not hold.  B. 
How it holds in Voluntary Agents we will then consider when our Method hath brought us to the Powers and Passions of the mind.  
A third Axiom shall be this: Whatsoever Body being at Rest is afterwards moved, hath for its Immediate Movent some other Body which is in Motion and toucheth it. For, since nothing can move itself, the Movent must be external. And because Motion is change of place, the Movent must put it from its place, which it cannot do till it touch it.  A. 
That is manifest, and that it must more than touch it, it must also follow it. And if more parts of the Body are moved than are by the Movent touched, the Movent is not Immediate. And by this reason, a continued Body though never so great, if the first Superficies be pressed never so little back, the Motion will proceed through it.  B. 
Do you think that to be impossible? I will prove it from your own words: For you say that the Movent does then touch the Body which it moveth. Therefore it puts it back; But that which is put back, puts back the next behind, and that again the next; and so onward to any distance, the body being continued. The same is also manifest by experience, seeing one that walks with a Staff can distinguish (though blind) between Stone and Glass; which were impossible, if the parts of his Staff between the ground and his hand made no resistance. So also he that in the silence of the night lays his Ear to the ground, shall hear the treading of men's feet further than if he stood upright.  A. 
This is certainly true of a Staff or other hard Body, because it keeps the Motion in a strait Line from diffusion. But in such a Fluid Body as the Air, which being put back must fill an Orb, and the further it is put back, the greater Orb, the Motion will decrease, and in time, by the resistance of Air to Air, come to an end.  B. 
That any Body in the world is absolutely at Rest, I think not true: But I grant, that in a space filled every where with Body, though never so Fluid, if you give Motion to any part thereof, that Motion will by resistance of the parts moved, grow less and less, and at last cease; but if you suppose the space utterly void, and nothing in it, than whatsoever is once moved shall go on eternally: Or else that which you have granted is not true, viz. That nothing can put an end to its own Motion.  A. 
But what mean you by resistance?  B. 
Resistance is the Motion of a Body in a way wholly or partly contrary to the way of its Movent, and thereby repelling or retarding it. As when a man runs swiftly, he shall feel the Motion of the Air in his face. But when two hard Bodies meet, much more may you see how they abate each others Motion, and rebound from one another. For in a space already full, the Movent cannot, in an instant, be communicated through the whole depth of the Body that is to be moved.  A. 
What other Definitions have I need of?  B. 
In all Motion, as in all Quantity, you must take the beginning of your reckoning from the least supposed Motion. And this I call the 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 Axioms 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, strait, circular, or otherwise crooked; and what degree of swiftness; as also the action of the Movent, whether Trusion, Vection, Percussion, Reflection, or Refraction; and further you must furnish yourself 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, 'tis 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 inquire the Cause of some Effect particular.  B. 
We will begin with that which is the most universal, the Universe, and inquire 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. 
'TIs 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. 
'Tis 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 sucked it, dip it presently at the neck into a basin of water, you shall manifestly see the water rise into the Vial. Is not this a certain sign that you had sucked 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 dipped into the water) it will penetrate and enter into it. For Air if it be pressed 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 Basin.  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 Child's 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 joined 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 pulled 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 stopped as to admit no Air; for then the Liquor will not run: but if the Tap-hole be large it will, because the Air pressed by a heavier Body 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 filled 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 Basin, 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 itself. 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 Basin according to the nature of heavy Fluids, but stay and stand above it at the height of 29 inches or very near it, the bottom being now uppermost that no Air can get in.  B. 
What do you infer from this?  A. 
That all the cavity above 29 inches is filled with Vacuum.  B. 
'Tis very strange that I, from this same Experiment, should infer (and I think evidently) that it is filled with Air. I pray, tell me, when you had inverted the Cylinder, full as it was, and stopped with your finger, dipped into the Basin, 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 pressed upward through the Quicksilver itself: For a man with his hand can easily thrust a Bladder of Air to the bottom of a Basin of Quicksilver.  B. 
It is therefore manifest that Quicksilver can press the Air through the same Quicksilver.  A. 
'Tis manifest; and also itself rise into the Air.  B. 
What cause then can there be, why it should stand still at 29 inches above the level of the Basin, rather than any place else?  A. 
'Tis not hard to assign the cause of that. For so much Quicksilver as was above the 29 inches, will raise the first levelly of that in the basin, as much as if you had poured 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 only 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 forced 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 leisurely.  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 pumped out; nor can that wooden Pestle be called a Sucker.  B. 
That's it I say. There is no Air either pumped 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 itself?  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 behind itself 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. IU. Of the Systeme of the World.  B. 
YOu are come in good time; let us 
Fig. 1.  therefore sit down. There is Ink, Paper, Ruler, and Compass. Draw a little Circle to represent the Body of the Sun.  A. 
'Tis done. The Centre is A, the Circumference is L M.  B. 
Upon the same Centre A, draw a larger Circle to stand for the Ecliptic: For you know the Sun is always in the Plain of the Ecliptic.  A. 
There ' 'tis. 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 Ecliptic, suppose the North-Pole; and than H will be East, and I West. And C A produced to the Circumference in E, maketh 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. 
'Tis drawn, and marked with l m. And B D and K G joined 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 Ecliptic 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 to b B m, the Line n G will be in the Ecliptic of the Earth, because G d is in the Aequator of the Earth. So that in the Annual Motion of the Earth through the Ecliptic, every straight Line drawn in the Earth, is perpetually kept parallel to the place from whence it is removed.  A. 
'Tis true; and 'tis the Doctrine of Copernicus. But I cannot yet conceive by what one Motion this Circle can be described otherwise than we are taught by Euclid. And then I am sure that all the Diameters shall cross one another in the Centre, which in this Figure is A.  B. 
I do not say that the Diameters of a Sphere or Circle can be parallel; but that if a Circle of a lesser Sphere be moved upon the Circumference of a great Circle of a greater Sphere, that the straight Lines that are in the lesser Sphere may be kept parallel perpetually to the places they proceed from.  A. 
How? And by what Motion?  B. 
Take into your hand any straight Line, (as in this Figure) the Line L A M, which we suppose to be the diameter of the Sun's Body; and moving it parallelly, with the ends in the Circumference, so as that the end M may withal describe a small Circle, as M a. It is manifest that all the other points of the same Line L M will by the same Motion, at the same time, describe equal Circles to it. Likewise if you take in your hand any two Diameters fastened together, the same Parallel-motion of the line L M, shall cause all the points of the other Diameter to make equal Circles to the same M a.  A. 
'Tis evident; as also that every point of the Sun's body shall do the like. And not only so, but also if one end describe any other Figure, all the other points of the Body shall describe like and equal Figures to it.  B. 
You see by this, that this Parallel-motion is compounded of two Motions, one Circular upon the Superficies of a Sphere, the other a straight Motion from the Centre to every point of the same Superficies, and beyond it.  A. 
I see it.  B. 
It follows hence, that the Sun by this Motion must every way repel the Air; and since there is no empty place for retiring, the Air must turn about in a Circular stream; but slower or swifter according as it is more or less remote from the Sun, and that according to the nature of Fluids', the Particles of the Air must continually change place with one another; and also that the stream of the Air shall be the contrary way to that of the Motion, for else the Air cannot be repelled.  A. 
All this is certain.  B. 
Well. Then if you suppose the Globe of the Earth to be in this stream which is made by the Motion of the Sun's Body from East to West, the stream of Air wherein is the Earth's Annual Motion will be from West to East.  A. 
'Tis certain.  B. 
Well. Then if you suppose the Globe of the Earth, whose Circle is moved Annually, to be l m, the stream of the Air without the Ecliptic falling upon the Superficies of the Earth l m without the Ecliptic, being slower, and the stream that falleth within swifter, the Earth shall be turned upon its own Centre proportionally to the greatness of the Circles; and consequently their Diameters shall be parallel; as also are other straight Lines correspondent.  A. 
I deny not but the streams are as you say; and confess that the proportion of the swiftness without, is to the swiftness within, as the Sun's Ecliptic to the Ecliptic of the Earth; that is to say, as the Angle HAB to the Angle m B b. And I like your Argument the better, because it is drawn from Copernicus his foundation. I mean the compounded Motion of Straight and Circular.  B. 
I think I shall not offer you many demonstrations of Physical conclusions that are not derived from the Motions supposed or proved by Copernicus. For those Conclusions in Natural Philosophy I most suspect of falsehood, which require most variety of Suppositions for their demonstrations.  A. 
The next thing I would know, is how great or little you suppose that Circle a M.  B. 
I suppose it less than you can make it: For there appears in the Sun no such Motion sensible. 'Tis the first Endeavour of the Sun's Motion. But for all that, as small as the Circle is, the Motion may be as swift, and of as great strength as 'tis possible to be named. 'Tis but a kind of trembling that necessarily happeneth in those Bodies, which with great resistance press upon one another.  A. 
I understand now from what Cause proceedeth the Annual Motion: Is the Sun the Cause also of the Diurnal Motion?  B. 
Not the immediate Cause. For the Diurnal Motion of the Earth is upon its own Centre, and therefore the Sun's Motion cannot describe it. But it proceedeth as a necessary consequence from the Annual Motion. For which I have both experience and demonstration. The Experiment is this: Into a large Hemisphere of Wood, spherically Concave, put in a Globe of Lead, and with your hands hold it fast by the brim, moving your hands circularly, but in a very small compass, you shall see the Globe circulate about the Concave Vessel, just in the same manner as the Earth doth every year in the Air; and you shall see withal, that as it goes, it turns perpetually upon its own Centre, and very swiftly.  A. 
I have seen it: And 'tis used in some great Kitchens to grind Mustard.  B. 
Is it so? Therefore take a Hemisphere of Gold (if you have it) the greater the better, and a Bullet of Gold, (and without Mustard) you shall see the same Effect.  A. 
I doubt it not. But the of it 'Cause is evident. For any Spherical Body being in Motion upon the sides of a Concave and hard Sphere, is all the way turned upon its own Centre by the resistance of the hard Wood or Metal. But the Earth is a Bullet without weight, and meeteth only with Air, without any harder body in the way to resist it.  B. 
Do you think the Air makes no resistance, especially to so swift a Motion as is the Annual Motion of the Earth? If it do make any resistance, you cannot doubt but that it shall turn the Earth circularly, and in a contrary way to its Annual Motion; that is to say, from East to West, because the Annual Motion is from West to East.  A. 
I confess it. But what deduce you from these Motions of the Sun?  B. 
I deduce (first) that the Air must of necessity be moved both circularly about the Body of the Sun according to the Ecliptic, and also every way directly from it. For the Motion of the Sun's Body is compounded of this Circular Motion upon the Sphere L M, and of the straight motion of its Semidiameters from the Centre A to the Superficies of the Sun's Body, which is LM. And therefore the Air must needs be repelled 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 Sun's 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 only 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 shown the Natural Causes of the Motions of the Stars. But that was no part of his design; which was only from his own observations, and those of former Astronomers, to compute the times of their Motions; partly to foretell the Conjunctions, Oppositions, and other Aspects of the Planets; and partly to regulate the times of the Church's Festivals. But his followers, Kepler and Galileo, make the Earth's 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 Sun's 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 Sun's 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 assign for this Excentricity?  B. 
Kepler ascribes it to a Magnetic virtue, viz. that one part of the Earth's 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 virtue 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 nearest to the Earth, when he is in the Winter-Solstice) I shall show you when we come to speak of the Motions of Air and Water.  A. 
That's time enough: For I intent 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 Ecliptic of the Fixed 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 straight 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 Ecliptic 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 near, 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 Ecliptic 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 Signs, Aries, Taurus, Gemini, etc. from West to East every 100 year one degree or very near.  A. 
In what time do they make the whole Revolution through the Ecliptic 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 Ptolemy 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 'tis a great sign that his Supposition is true. But what is the Cause that the Obliquity of the Ecliptic, that is, the distance between the Aequinoctial and the Solstice, is not always the same?  B. 
The necessity of the Obliquity of the Ecliptic 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 are u s descending to s. But in the arc s u, and its alternate rising to C. The cause of the twining is the Earth's Annual Motion the same way in the Ecliptic, 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 fixed Stars near that which is called Cynosura.  B. 
No: 'Tis 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 fixed Stars, when 'tis so unlikely that all the fixed 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 fixed 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 only 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, nearer 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 Sunbeams piercing them have appeared like a Beard; and why might not such a Beard have appeared to you like a Comet, if you had looked 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 add not a little to the Motion of the Sea: Which were impossible if it did not add 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 find what part of a Circle the Diameter of the Sun's Body doth subtend in the Ecliptic Circle.  B. 
Kepler says it subtends 30 minutes, which is half a degree. His way to find it is by letting in the Sunbeams 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 Sun's 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 shows 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 bade 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 pressed or bend, 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 itself) but it is the Motion of the parts which are not pressed, 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 ebb 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 Strait of Magellan Eastward to the Indies, and thence to the same Strait again? And is not there a great Sea called the Atlantic 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 forced to do by this compounded Motion, which is a kind of succussion of the Earth, and fills both the Atlantic 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 Basin the water would be thrown into the Air, yet the Earth cannot throw the Sea into the Air.  A. 
Yes. The Basin, 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 checked. For at the Strait of Magellan, the great South-Sea is checked 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 checked again and forced through the Atlantic into the British and Germane Seas. And this is done every day. For we have supposed that the Earth's Motion in the Ecliptic 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 nearer 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 Ecliptic, it will be yet greater, because the Moon than 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. 
'Tis evident. And 'tis 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 Situation. For the Current of the Ocean through the Atlantic 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 Atlantic Sea, and those Sands on the Coast of Lincolnshire directly opposite to the Current of the Germane 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 shows 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. 
'Tis 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 show me that the cause of it is this compounded Motion, I shall go near to think it the Cause of all other Effects of Nature hitherto disputed of. The Experiment is common, and described by the Lord Chancellor 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 myself, and found true not only 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 itself 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 heavy 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 shown 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 heavy) easily carried up and down with the Wind, till, meeting with some Mountain or other Clouds, they be pressed together into greater drops, and fall by their weight. So also it is forced up in moist ground, and with it many small Atoms 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 Tropic of Capricorn. And this Climate is that which makes the Sun's Perigaeum to be always on the Winter-Solstice. And that is the part of the Terrestrial Globe which Keplerus says is kind 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 virtue 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 nearer to it, together with the water which it raiseth.  A. 
Can you guests 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 itself from being penned up in a strait. For when a Cloud descendeth, it makes no wind sensible directly under itself. But the Air between it and the Earth is pressed 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 engendered in the Caverns of the Earth by Condensation of the Air.  B. 
I wonder he should say that. I have passed over that Hill twice since the time I read that in Scaliger, and found that River as I passed, 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 myself 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 Peripatetics) it is a thing incogitable, and the words are insignificant. For by Densum is signified only frequency 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 Atlantic Sea called Spouts, which pour down water enough at once to drown a great Ship?  B. 
'Tis a thing I have not seen. And therefore can say nothing to it; though I doubt not but when two very large and heavy 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, pressed by the Substance of the Glass which is dipped into it, do rather rise into a very small Pipe, than come about a longer way into the open Air.  A. 
'Tis very probable. I observed also that the top of the enclosed 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 Basin 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 only because it is heavy (for if the rag lay higher without than within, and were made heavier by the breadth, it would not descend) but 'tis because all heavy 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. 
'TIs 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 yourself, but not that the Sun is hot. But when you find yourself 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 mind; 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 showed you yesterday in discoursing of Rain, how by this compounded Motion of the Sun's 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 loser parts of your hand, an Endeavour to get forth, which will extend the skin, and in some climates fetch up the blood, and in time make the skin black. The Fire also will do the same to them that often sit with their naked skins too near it. Nay, one may sit so near (without touching it) as it shall blister or break the skin, and fetch up both spirits and blood mixed into a putrid oily matter sooner, than in a Furnace Oil 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 Atoms of the Fuel 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, straight, 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 stricken 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 itself, is evident enough by this, that the Sunbeams 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 Wind 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 Satire that dwelling with a Husbandman, and seeing him blow his fingers to warm them, and his Pottage to cool it, was so scandalised, 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 itself. 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 daily 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 Ecliptic.  A. 
Does not the Earth make the Wind as great in one part of the Ecliptic 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 only, 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 'twas thought) a want of the same) they inferred that the greatest Cold must be about the Poles of the Aequinoctial. Wherein they miscounted. For not every Motion causeth Heat, but this agitation only, which we call compounded Motion; though some have alleged Experience for that opinion; as that a Bullet out of a Gun will with its own swiftness melt. Which I never shall believe.  A. 
'Tis 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 itself 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 mixed; 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 'tis 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 washed 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 situated 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, 'tis 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 itself; but not without some abatement in the Stream of the Air that hardened it; as when the Sunbeams are less oblique to the Earth, or some contrary Wind resisteth the stream of the Air. For when the impediment is removed, than the nature of the water only worketh, and (being a heavy Body) downward.  A. 
I forgot to ask you, Why two pieces of Wood rubbed swiftly one against another, will at length set on fire.  B. 
Not only 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 fly swiftly out; whereby the Air driven to the Eye of the beholder, maketh that fancy 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 Charcoal, Brimstone, and Saltpetre? Whereof the first will kindle with a spark, the second flame as soon as touched with fire; and the third blows it, as being composed of many Orbs of Salt filled 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 itself 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 'tis 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 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 find 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 signify the curling of water by the Wind; and use the same also for Horror, 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 shows 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 Queries. 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 'tis only in Summer, and in hot weather, that it Thunders; or if in Winter, it is taken for a Prodigy. 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 straightened with Islands, so must the Current of Air made by the Annual Motion be swiftest there, where it is checked with many Clouds through which it must (as it were) be strained, and leave behind 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 enclosed 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, than a great part of the Ice breaks: And this is the Thunderclap. The Murmur following is from the settling of the Air. The Lightning is the fancy 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 killed men with Cold. But this extraordinary swiftness of Lightning consisteth not in the Expansion of the Air, but in a strait 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 only 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, etc. 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 Politics, yet there is very little Natural Philosophy to be gathered out of their Writings.  B. 
Their Ethiques and Politics are pleasant reading, but I find not any argument in their discourses of Justice or Virtue drawn from the supreme Authority, on whose Laws all Justice, Virtue, and good Politics 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 Atoms that fly 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 find any tolerable method of enquiry. But I resolved at last to begin with the Questions concerning Hard and Soft, and what kind 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 subtle 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 only 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 hardened into Ice, you have told me already, and I understand it. But how a soft Homogeneous Body, as Air, or Water, should be so hardened, 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 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 hardened. The Club-end of it A A coming first to the water, the tail B C following it. 'Tis 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. 'Tis therefore manifest that the Motion which hardeneth 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 bend 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 Sunbeams 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 softened again, may be re-hardned; but how a Fluid and mere Homogeneous Body, as Air or Water, may be so, I see not yet. For the hardening 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 mere Air, which hath no Natural Motion of itself, but is moved only by other Bodies of a greater consistence, I think it impossible to be hardened. For the parts of it so easily change places, that they can never be fixed 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 Crystal; and they allege Experience for it. For they say that Crystal is found hanging on high Rocks in the Alps like Icicles 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 Crystal: Which cannot be, because Crystal 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 workhouse a Billet of Wood, as I thought it, partly covered with bark, and partly with the grain bare, as long as a man's Arm, and as thick as the Calf of a man's Leg; which handling I found extreme heavy, 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 nearest to Stone. I have seen also a kind of Slate painted naturally with Forest-work. And I have seen in the hands of a Chemist 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 show 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 guests, nor guests 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, Atoms) that were made Hard in the beginning, and consequently by an Eternal Cause; and that the hardness of the whole Body is caused only 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 only 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, than 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 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 Springtime 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, etc. 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 only weaken it, but also cause it falsely 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 bend, 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 bend, 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. 
'Tis 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 Heavy to be so too, and many liquors also besides water.  A. 
Why then do men say they find 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 itself (being a heavy Body) without it cannot do. What kind of substance these Atoms 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 only in or near 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 near to their habitation. Which in time fermenting breed Worms, which commonly in a month or little more, naturally become Flies; and though engendered at one Town, may fly to another. Secondly, in the beginning of a Plague, those that dwell in the Suburbs, that is to say, nearest 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 'tis 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 only 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 find some medicine to fright them from mingling with our breath. But what is that which kills men that lie asleep too near a Charcolefire? Is it another kind of Fly? Or is Charcoal venomous?  B. 
It is neither Fly nor venom, but the Effect of a flameless glowing fire, which dissipates those Atoms 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. 
'Tis 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 find 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, that they might have called it an intrinsical Motion rather than an intrinsical 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 'tis 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 inquires no further than, Why so much water (being a heavy 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 intent 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 heavy (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 itself beneath it.  B. 
It appears by Experience, but not by this Argument, though instead of Water the Tub were filled with Quicksilver.  A. 
I thought so. But how it comes to pass that the Fish remains uncrushed, I cannot tell.  B. 
The Endeavour of the Quicksilver downward, is stopped 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 heavy, and thereby the Endeavour of the Quicksilver is diverted to the sides roundabout; where stopped 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 only, 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 Pyramid of Brick, wherein the Bricks are so joined, that the uppermost lies every where over the joint 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 crushed nor hurt in the bottom of the Sea by the weight of the water, is the waters arching itself, 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 itself 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 dwelled 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 find 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) intrinsical, 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 allegeth this, That Water left to itself without disturbance, does naturally settle itself 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 heavy 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 Basin, but in half a mile at Sea, Experience visibly shows 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 says he further concerning Gravity?  A. 
He takes for granted (not as an Experiment, but an Axiom) that Nature worketh not by election, but ad ultimum virium, with all the power it can.  B. 
I think he means (for 'tis a very obscure passage) that every inanimate Body by nature worketh all it can without election; which may be true. But 'tis 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 sense 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 meddling with things of such difficulty? He will find 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 
Fig. 3.  be a Siphon A B C D filled with Quicksilver to the level A D. If then you pour Oil upon A as high as to E, he asketh if the Oil in A E (as being heavy) 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 only 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 Oil 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 heavy Bodies in their descending, as to leave the Oil, so that it should not only 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 Oil to either Scale, will make it praeponderate. And that was it deceived him.  A. 
'Tis evident. The last Experiment he citys is the weighing of Air in a pair of Scales, where 'tis 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 pressed downward by the weight of the blown Bladder, so much will rise from below, and lay itself Spherically at the altitude of the Centre 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 balance it. Therefore the Experiment proves nothing to his purpose. And whereas they say there be small heavy 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 clearly resolved, because the water tending every way to one point (which is the Centre of the Earth) must of necessity arch itself. 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 showed 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) Led, is more than I hope to know, or mean to inquire: for I doubt not but that the Species of heavy, hard, Opaque, and Diaphanous, were all made so at their creation, and at the same time separated from different Species. So that I cannot guests 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 Kinds of Hard, and Heavy, 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 show 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 heavy 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 Heavy. But it doth not. For the hardest Bodies are not always the heaviest. Therefore I find no access that way to compare the Causes of different Endeavours of heavy Bodies to descend.  A. 
But show me at least how any heavy 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. 
'Tis already granted, that the Earth hath this compounded Motion supposed by Copernicus, and that thereby it casteth the Contiguous Air from itself every way roundabout. Which Air so cast off, must continually by its nature, range itself in a Spherical Orb. Suppose a Stone (for instance) were taken up from the ground, and held up in the Air by a man's hand, what shall come into the place it filled when it lay upon the Earth?  A. 
So much Air as is equal to the Stone in magnitude, must descend and place itself 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 itself in that, and so perpetually to the man's 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. 
'Tis just so. And further, the Motion of the Stone downward shall continually be accelerated according to the odd 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 'tis 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 heavy 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 nearer and nearer to the Earth, become more and more slender, in the form of a Solid Sector? And if it have far to go, divide itself 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 considered 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 pressed 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 mixed 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 fixed Star, it would return to the Earth.  B. 
'Tis 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 itself 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 itself upon it.  B. 
The reason I think is manifest. For those Bodies which are made by beating of Water and Air together, show 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, etc. 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, etc. 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 ask concerning Gravity. If Gravity be (as some define it) an intrinsical quality, whereby a Body descendeth towards the Centre of the Earth, how is it possible that a piece of Iron that hath this intrinsecal quality, should rise from the Earth, to go to a Loadstone? Hath it also an intrinsical quality to go from the Earth? It cannot be. The Cause therefore must be extrinsical. And because when they are come together in the Air, if you leave them to their own nature, they will fall down together, they must also have some like extrinsical Cause. And so this magnetic virtue will be such another virtue as makes all other heavy Bodies to descend (in this our World) to the Earth. If therefore you can from this your Hypothesis of compounded Motion, by which you have so probably salved the Problem of Gravity, salve also this of the Loadstone, I shall acknowledge both your Hypothesis to be true, and your Conclusion to be well deduced.  B. 
I think it not impossible. But I will proceed no further in it now, than (for the facilitating of the demonstrations) to tell you the several proprieties of the Magnet, whereof I am to show the causes. As first, That Iron, and no other Body, at some little distance (though heavy) will rise to it. Secondly, That if it be laid upon a still Water in a floating Vessel, and left to itself, it will turn itself till it lie in a Meridian, that is to say, with one and the same Line still North and South. Thirdly, If you take a long slender piece of Iron, and apply the Loadstone to it, and (according to the position of the Poles of the Loadstone) draw it over to the end of the Iron, the Iron will have the same Poles with the Magnet, so it be drawn with some pressure; but the Poles will lie in a contrary Position; and also this long Iron will draw other Iron to it as the Magnet doth. Fourthly, This long Iron, if it be so small as that poised upon a Pin, the weight of it have no visible Effect, the Navigators use it for the Needle of their Compass, because it points North and South; saving that in most places by particular accidents it is diverted; which diversion is called the variation of the Horizontal Needle. Fifthly, The same Needle placed in a Plain perpendicular to the Horizon, hath another Motion called the Inclination. Which that you may the better conceive, draw a fourth 
Fig. 4.  Figure; wherein let there be a Circle to represent the Terrella, that is to say, a Spherical Magnet.  A. 
Let this be it, whose Centre is A, the North Pole B, the South Pole C.  B. 
Join B C, and cross it at right Angles with the Diameter D E.  A. 
'Tis done.  B. 
Upon the point D set the Needle parallel to B C, with the cross for the South Pole, and the Barb for the North; and describe a Square about the Circle B D C E, and divide the arch D B into four equal parts in a, b, c.  A. 
'Tis done.  B. 
Then place the middle of the Needle on the points a, b, c, so that they may freely turn; and set the Barb which is at D toward the North, and that which is at C towards the South. You see plainly by this, that the Angles of Inclination through the Arch D C taken all together, are double to a Right Angle. For when the South point of the Needle, looking North, as at D, comes to look South, as at C, it must make half a Circle.  A. 
That is true. And if you draw the Sine of the Arch D a (which is d a) and the Sine of the Arch B a (which is a c) and the Sine of the Arch D b (which is b f) and the Sine of the Arch B c (which is c g) the Needle will lie upon b f with the North-point downwards, so that the Needle will be parallel to A D. Then from a draw the line a h, making the Angle e a h equal to the Angle D A a. And then the Needle at a shall lie in the line a h with the South point toward h. Finally, draw the line c h, which (with c g) will also make a quarter of a right Angle; and therefore if the Needle be placed on the point c it will lie in c h with the South point toward h. And thus you see by what degrees the Needle inclines or dips under the Horizon more and more from D till it come to the North Pole at B; where it will lie parallel to the Needle in D; but with their Barbs looking contrary ways. And this is certain by experience, and by none contradicted.  B. 
You see then why the degrees of the Inclinatory Needle in coming from D to B are double to the degrees of a Quadrant. It is found also by experience, that Iron both of the Mine and of the Furnace put into a Vessel so as to float, will lay itself (if some accident in the Earth hinder it not) exactly North and South. And now I am, from this compounded Motion supposed by Copernicus, to derive the causes why a Loadstone draws Iron; why it makes Iron to do the same; why naturally it placeth itself in a parallel to the Axis of the Earth; why by passing it over the Needle it changes its Poles; and what is the cause that it inclines. But it is your part to remember what I told you of Motion at our second meeting; and what I told you of this compounded Motion supposed by Copernicus, at our fourth meeting.   

CAP. IX. Of the Loadstone, and its Poles; and whether they show the Longitude of places on the Earth.  A. 
I Come now to hear what Natural Causes you can assign of the virtues of the Magnet; and first, why it draws Iron to it, and only Iron.  B. 
You know I have no other cause to assign but some local Motion, and that I never approved of any argument drawn from Sympathy, Influence, Substantial Forms, or Incorporeal Effluvia. For I am not, nor am accounted by my Antagonists for a Witch. But to answer this Question, I should describe the Globe of the Earth greater than it is at B in the first Figure, but that the Terrella in the fourth Figure will serve our turn. For 'tis but calling B and C the Poles of the Earth, and D E the Diameter of the Aequinoctial Circle, and making D the East, and E the West. And then you must remember that the Annual Motion of the Earth is from West to East, and compounded of a strait and circular Motion, so as that every point of it shall describe a small Circle from West to East, as is done by the whole Globe. And let the Circles about a b c be three of those small Circles.  A. 
Before you go any further, I pray you show me how I must distinguish East and West in every part of this Figure. For wheresoever I am on Earth (suppose at London) and see the Sun rise (suppose in Cancer) is not a strait line from my Eye to the Sun terminated in the East?  B. 
'Tis not due East, but partly East, partly South. For the Earth (being but a point compared to the Sun) all the parallels to D E the Aequator, such as are e a, f b, e g, if they be produced, will fall upon the Body of the Sun. And therefore A b is North-East; A a East North-East; And A c North North-East.  A. 
Proceed now to the Cause of Attraction.  B. 
Suppose now that the Internal parts of the Loadstone had the same Motion with that of the Internal parts of the Sun which make the Annual Motion of the Earth from West to East, but in a contrary way, for otherwise the Loadstone and the Iron can never be made to meet. Then set the Loadstone at a little distance from the Earth, marked with z; and the Iron marked with x upon the superficies of the Earth. Now that which makes x rise to z, can be nothing else but Air; for nothing touches it but Air. And that which makes the Air to rise, can be nothing but those small circles made by the parts of the Earth (such as are at a b c,) for nothing else touches the Air. Seeing then the Motion of each point of the Loadstone is from East to West in Circles, and the motion of each point of the Iron from West to East; it follows, that the Air between the Loadstone and the Iron shall be cast off both East and West; and consequently the place left empty, if the Iron did not rise up and fill it. Thus you see the Cause that maketh the Loadstone and the Iron to meet.  A. 
Hitherto I assent. But why they should meet when some Heterogeneous Body lies in the Air between them, I cannot imagine. And yet I have seen a Knife, though within the Sheath, attract one end of the Needle of a Mariner's Compass; and have heard it will do the same though a Stone-wall were between.  B. 
Such Iron were indeed a very and vigorous Loadstone. But the Cause of it is the same that causeth Fire or hot Water (which have the same compounded Motion) to work through a Vessel of Brass. For though the Motion be altered by restraint within the Heterogeneous Body, yet being continued quite through it restores itself.  A. 
What is the Cause why the Iron rubbed over by a Loadstone will receive the virtue which the Loadstone hath of drawing Iron to it?  B. 
Since the Motion that brings two Bodies to meet must have contrary ways, and that the Motions of the Internal parts of the Magnet and of the Iron are contrary; the rubbing of them together does not give the Iron the first Edeavour to rise, but multiplies it. For the Iron untouched will rise to a Loadstone; but if touched, it becomes a Loadstone to other Iron. For when they touch a piece of Iron they pass the Loadstone over it only one way, viz. from Pole to Pole; not back again, for that would undo what before had been done; also they press it in passing, to the very end of the Iron, and somewhat hard. So that by this pressing Motion all the small Circles about the points a b c, are turned the contrary way. And the halves of those small Circles made on the Arch D B will be taken away, and the Poles changed, so as that the North-Poles shall point South, and the South Poles North, as in the Figure.  A. 
But how comes it to pass, that when a Loadstone hath drawn a piece of Iron, you may add to it another, as if they begat one another? Is there the like Motion in the generation of Animals?  B. 
I have told you that Iron of itself will rise to the Loadstone. Much more than will it adhere to it when it is armed with Iron, and both it and the Iron have a plain Superficies. For than not only the points of Contact will be many (which make the coherence stronger) but also the Iron wherewith it is armed is now another Loadstone, differing a little (which you perhaps think) as Male and Female. But whether this compounded Motion and confrication causeth the generation of Animals, how should I know, that never had so much leisure as to make any observation which might conduce to that?  A. 
My next Question is, seeing you say the Loadstone, or a Needle touched with it, naturally respecteth the Poles of the Earth, but that the variation of it proceedeth from some accidents in the Superficies of the Earth; what are those accidents?  B. 
Suppose there be a Hill upon the Earth (for example) at r; then the stream of the Air which was between z and x Westward, coming to the Hill, shall go up the Hills side, and so down to the other side, according to the crooked Line which I have marked about the Hill by points; and this infallibly will turn the North-point of the Needle, being on the East side, more toward the East, and that on the other side more towards the West, than if there had been no Hill. And where upon the Earth are there not Eminencies and depressions, except in some wide Sea, and a great way from Land?  A. 
But if that be true, the Variation in the same place should be always the same. For the Hills are not removed.  B. 
The Variation of the Needle at the same place is still the same: but the Variation of the Variation is partly from the Motion of the Pole itself, which by the Astronomers is called Motus trepidationis; and partly from that, that the Variation cannot be truly observed: for the Horizontal Needle and the Inclinatory Needle incline alike, but cannot incline in due quantity. For whether set upon a Pin or an Axis, their Inclination is hindered in the Horizontal Needle by the Pin itself. If upon an Axis, if the Axis be just, it cannot move; if slack, the weight will hinder it. But chiefly because the North Pole of the Earth draws away from it the North Pole of the Needle. For two like Poles cannot come together. And this is the cause why the Variation in one place is East, and another West.  A. 
This is indeed the most probable reason why the Variation varies, that ever I heard given. And I should presently acknowledge that this parallel Motion of the Axis of the Earth in the Ecliptic, supposed by Copernicus, is the true Annual Motion of the Earth, but that there is lately come forth a Book called Longitude found, which makes the Magnetical Poles distant from the Poles of the Earth eight Degrees and a half.  B. 
I have the Book. 'Tis far from being demonstrated, as you shall find if you have the patience to see it examined. For wheresoever his demonstration is true, the conclusion (if rightly inferred) will be this, that the Poles of the Loadstone and the Poles of the Earth are the same. And where on the contrary his demonstrations are fallacies, it is because sometimes he fancieth the Lines he hath drawn, not where they are; sometimes because he mistakes his station; and sometimes because he goes on some false Principle of Natural Philosophy; and sometimes also because he knoweth not sufficiently the Doctrine of Spherical Triangles.  A. 
I think that's the Book there which lies at your Elbow. Pray you read.  B. 
I find first (Pag. 4.) that the ground of his Argument are the two observations made by Mr. Burroughs; one at Vaygates, in 1676, where the Variation from the Pole of the Earth he found to be 11 deg. 15 min. East; the other at Limehouse near London, in 1580, where the Variation from the Pole of the Earth was 8 deg. 38 min. West. By which he saith, he might find out the Magnetical Pole.  A. 
Where is Vaygate?  B. 
In 70 Degrees of North Latitude, the difference of Longitude between London and it being 58 Degrees.  A. 
The Longitude of places being yet to seek, how came he to know this difference of 58 Degrees, except the Poles of the Magnet and the Earth be the same?  B. 
I believe he trusted to the Globe for that. For the distance between the places is not above 2000 Miles the nearest way. But we will pass by that, and come to his Demonstration, and to his Diagram, wherein L is London, P the North-Pole of the Earth, V Vaygates. So that L P is 38 deg. 28 min. P V 20 deg. the Angle L P V 58 deg. for the difference between the Longitudes of Vaygates and London. This is the Construction. But before I come to the demonstration, I have an Inference to draw from these observations, which is this. Because in the same year the Variation at London was 11 deg. 15 min. East, and at Vaygates 8 deg. 38 min. West; If you subtract 11 deg. 15 min. from the Arc L P; and 8 deg. 38 min. from the Arc L V, the Variation on both sides will be taken away; so that P V being the Meridian of Vaygates, and L P the Meridian of London, they shall both of them meet in P the Pole of the Earth. And if the Pole of the Magnet be nearer to the Zenith of London than is the Pole of the Earth, it shall be just as much nearer to the Zenith of Vaygates in the Meridian of Vaygates which is P V; as is manifest by the Diurnal Motion of the Earth.  A. 
All this I conceive without difficulty. Proceed to the Demonstration.  B. 
Mark well now. His words are these, (Pag. 5.) From P L V subtract 11 deg. 15 min. and there remains the Angle V L M. Consider now which is the Angle P L V, and which is the remaining Angle V L M, and tell what you understand by it.  A. 
He has marked the Angle P L V with two numbers, 11 deg. 15 min. and 21 deg. 50 min. which together make 33 deg. 5 min. And the Angle 11 deg. 15 min. being substracted from P L V, there will remain 21 deg. 50 min. for the Angle V L M. I know not what to say to it. For I thought the Arc P V, which is 20 deg. had been the Arc of the Spherical Angle P L V; and that the Arc L V had been 58 deg. because he says the Angle L P V is so; and that the Arc L M had been 46 deg. because the Angle L P M is so; and lastly, that the Angle P L M had been 8 deg. 30 min. because the Arc P M is so.  B. 
And what you thought had been true, if a Spherical Angle were a very Angle. For all Men that have written of Spherical Triangles take for the ground of their calculation (as Regiomontanus, Copernicus, and Clavius,) that the Arch of a Spherical Angle is the side opposite to the Angle. You should have considered also that he makes the Angle V P M 12 deg. but sets down no Arc to answer it. But that you may find I am in the right, look into the Definitions which Clavius hath put down before his Treatise of Spherical Triangles, and amongst them is this; The Arc of a Spherical Triangle is a part of a great Circle intercepted between the two sides drawn from the Pole of the said great Circle.  A. 
The Book is nothing worth; for it is impossible to subtract an Arc of a Circle out of a Spherical Angle. And I see besides that he takes the Superficies that lieth between the sides L P and L M for an Arch, which is the quantity of an Angle; and is a Line, and cannot be taken out of a Superficies. I wonder how any Man that pretends to Mathematics could be so much mistaken.  B. 
'Tis no great wonder. For Clavius himself striving to maintain that a right Angle is greater than the Angle made by the Diameter and the Circumference, fell into the same error. A corner (in Vulgar Speech,) and an Angle (in the Language of Geometry) are not the same thing. But it is easy even for a learned Man sometimes to take them for the same, as this Author now has done; and proceeding he saith, Subtract 8 deg. 38 min. from the Angle P V L, and there remains the Angle L V M.  A. 
That again is false, because impossible. What was it that deceived him now?  B. 
The same misunderstanding of the nature of a Spherical Angle. Which appears further in this, that when he knew the Arc V P was part of a great Circle, he thought V M (which he maketh 8 deg. 30 min.) were also parts of a great Circle; which is manifestly false. For two great Circles (because they pass through the Centre) do cut each other into halves. But P V is not half a Circle. He sure thought himself at Vaygates, and that P M V was equal to P V, although in the same Hemisphere.  A. 
But how proves he that the Arc PM is 8 deg. 30 min?  B. 
Thus. We have in two Triangles, P L M and P V M, two sides and one Angle included, to find P M the distance of the Magnetical Pole from the Pole of the Earth 8 deg. 30 min.  A. 
Is that all? 'Tis very short for a Demonstration of two so difficult Problems, as the quantity of 8 deg. 30 min. and of the place of the Magnetical Pole. But he has proved nothing till he has showed how he found it. And though P M be 8 deg. 30 min. it follows not that M is the Magnetical Pole.  B. 
Nor is it true. For if P M be 8 deg. 30 min. and V M 8 deg. 38 min. the whole Arc P M V will be 17 deg. 8 min. which should be 20 deg. Besides, whereas the Variations were East and West, the substracting of them should be also East and West, but they are North and South.  A. 
I am satisfied that the Magnetical Poles and the Poles of the Earth are the same. But thus much I confess, that if they were not the same, the Longitude were found. For the difference of the Latitudes of the Earth's Aequator and of the Magnetical Aequator is the difference of the Longitude. But proceed.  B. 
The Earth being a solid Body, and the Magnetic Sphere that encompasseth the Earth being a substance that hath not solidity to keep pace with the Earth, looseth in its Motion. And that may be the Cause of the Motion of the Magnetic Poles from East to West.  A. 
This is very fine, and unexpected. The Magnetic Sphere (which I took for a Globe made of a Magnet) has not solidity to keep pace with the Earth, though it be one of the hardest Stones that are. It encompasseth the Earth; yet I thought nothing had encompassed the Earth but Air in which I breath and move. By this also the whole Earth must be a Loadstone. For two Bodies cannot be in one place. So that he is yet no further than Dr. Gilbert whom he sleights. And if the Sphere be a Magnet, than the Earth and Loadstone have the same Poles. See the force of Truth! which though it could not draw to it his reason, hath drawn his words to it.  B. 
But perhaps he meant that the Magnetic virtue encompasseth the Earth, and not the Magnetic Body.  A. 
But that helpeth him not. For if the Body of the Magnet be not there, the virtue than is the virtue of the Earth; and so again the Poles of the Earth are Magnetic Poles.  B. 
You see how unsafe it is to boast of Doctrines as of God's gifts, till we are sure that they are true. For God giveth and denieth as he pleaseth, not as ourselves wish; as now to him he hath given Confidence enough, but hath denied him (at least hitherto) the finding of the Longitudes. In the next place (Pag. 8.) he seems much pleased that his Doctrine agrees with an opinion of Keplerus, That from the Creation to the year of our Lord it is to the year 1657 now 5650 years; and with that which he saith some Divines have held in times past, That as this World was created in six days, so it should continue six thousand years. By which account the World will be at an end 350 years hence; though the Scripture tell us it shall come as a Thief in the night. O what advantage 340 years hence will they have that know this, over them that know it not, by taking up Money at Interest, or selling Lands at 20 years' purchase!  A. 
But he says he will not meddle with that.  B. 
Yes, when he had meddled with it too much already.  A. 
But you have not told me wherein consisteth this Agreement between him and Keplerus.  B. 
I forgot it. 'Tis in the Motion of the Magnetic Poles. For precedently (Pag. 7.) he had said that their Period or Revolution was 600 years; their yearly Motion 36 min. and (Pag. 8.) that their Motion is by six. Six tenths of a degree in one year; six degrees in ten year; sixty degrees in a hundred year; and six times sixty degrees in 600 year.  A. 
But what Natural Cause doth he assign of this revolution of 600 years?  B. 
None at all. For the Magnet lying upon the Earth, can have no Motion at all but what the Earth and the Air give it. And because it is always at 8 deg. 30 min. distance from the Pole of the Earth, the Earth can give it no other Motion than what it gives to its own Poles by the precession of the Aequinoctial points. Nor can the Air give it any Motion but by its Stream; which must needs vary when the Stream varieth. But what a vast difference does he make between the period of the Motion of the Aequinoctial points, which are about or near 36000 years according to Copernicus (Lib. 3. Cap. 6.) which makes the Annual precession to be 36 seconds, and the period of the Magnetical Poles Motion, which is but 600 years.  A. 
Go on.  B. 
He comes now (Pag. 15.) to the Inclinatory Needle upon a Spherical Loadstone. Where he shows, by Diagram, that the Needle and the Instrument together moved toward the Magnetical Pole, make the sum of the Inclinations equal to two Quadrants, setting the North-point of the Needle Southward. Which I confess is true. But (in the same Page) he ascribeth the same Motion to the Earth in these words: As the Horizontal Needle hath a double Motion about the Round Loadstone or Terrulla, so also the Inclinatory Needle hath a double Motion about the Earth. What is this, but a confession that the Poles of the Magnet and of the Earth are the same?  A. 
'Tis plain enough.  B. 
Besides, seeing he placeth the Magnetical Pole at M in the Meridian of Vaygates, the Needle being touched shall Incline to the Pole of the Earth which is P, as well there as at London, and make the North-Pole of the Earth point South.  A. 
'Tis certain, because he puts both the Magnetical Pole and the Pole of the Earth in the same Meridian of the Earth. Nor see I any Cause why, the Needle being the same, it should not be as subject to Variation, and to Variation of Variation, and to all Accidents of the Earth there, as in any other part.  B. 
He putteth (Pag. 16.) a Question, At what distance from the Earth are the Magnetic Poles? and answers to it, They are very near the Earth, because the nearer the Earth, the greater the strength. What think you of this?  A. 
I think they are in the Superficies of the Magnet, as the Pole of the Earth is in the Superficies of the Earth. And consequently, that then the Earth must be a part of the Magnet, and their Poles the same. For the Body of the Magnet and the Body of the Earth, if they be two, cannot be in one place.  B. 
His next words are, Some things are to be considered concerning those Variations of the Horizontal Needle which are not according to the situation of the place from the Magnetic Poles, but are contrary; as all the West-Indies according to the Poles should be Easterly, and they are Westerly. Which is by some Accidental Cause in the Earth; and their Motion, as I formerly said, is a forced Motion, and not Natural.  A. 
He has clearly overthrown his main Doctrine. For to say the Motion of the Needle is forced and unnatural, is a most pitiful shift, and manifestly false, no Motion being more constant or less accidental, notwithstanding the Variation, to which the Inclinatory Needle is no less subject than the Horizontal Needle.  B. 
That which deceived him, was, that he thought them two sorts of Needles, forgetting what he had said of Normans Invention of the Inclinatory Needle by the inclining of the Horizontal Needle, Pag. 11. For I will show you that what he says is Easterly and should be Westerly, should be Easterly as it is. Consider the fourth Figure, in which B is the North-Pole, and B c 11 deg. 15 min. Easterly, which was the Variation at London in 1576 Easterly. Suppose A c to be the Needle, shall it not incline, as well here as at D a, and the Variation B c be Easterly? Again, D a is 11 deg. 15 min. and the Needle in D parallel to A B, and at a inclining also 11 deg. 15 min. Westerly. And is not the Variation there D a Westerly, with the North-point of the Needle in the Line a h?  A. 
But the West-Indies are not in this Hemisphere B C D E. The Variation therefore will proceed in an Arc of the opposite Hemisphere, which is Westerly.  B. 
I believe he might think so, forgetting that he and his Compass were on the Superficies of the Earth, and fancying them in the Centre at A.  A. 
'Tis like enough. If we had a strait Line exactly equal to the Arc of a Quadrant, I think it would very much facilitate the Doctrine of Spherical Triangles.  B. 
When you have done with your Questions of Natural Philosophy, I will give you a clear Demonstration of the equality of a strait Line to the Arc of a Quadrant, which, if it satisfy you, you may carry with you, and try thereby if you can find the Angle of a Spherical Triangle given.  A. 
It is time now to give over. And at our next meeting I desire your opinion concerning the Causes of Diaphaniety, and Refraction. This Copernicus has done much more than he thought of. For he has not only restored to us Astronomy, but also made the way open to Physiology.   

CAP. X. Of Transparence, Refraction; and of the Power of the Earth to produce living Creatures.  A. 
THinking upon what you said yesterday, it looked like a generation of living Creatures. I saw the love between the Loadstone and the Iron in their mutual attraction, their engendering in their close and contrary Motion; and their issue in the Iron, which being touched hath the same attractive virtue. Now seeing they have the same internal motion of parts with that of the Earth, why should not their substance be the same, or very near a kin?  B. 
The most of them (if not all) that have written of this Subject, when they call the Loadstone a Terrella, seem to think as you do. But I, except I could find proof for it, will not affirm it. For the Earth attracteth all kind of Bodies but Air, and the Loadstone none but Iron. The Earth is a Star, and it were too bold to pronounce any sentence of its substance, especially of the Planets, that are so leapt up in their several Coats, as that they cannot work on our Eyes, or any Organ of our other Senses.  A. 
I come therefore now to the business of the day. Seeing all Generation, Augmentation, and Alteration is local Motion, how can a Body not Transparent be made Transparent?  B. 
I think it can never be done by the Art of Man. For as I said of Hard and Heavy Bodies in the Creation, so I think of Diaphanous, that the very same Individual Body which was not Transparent then, shall never be made Transparent by Humane Art.  A. 
Do not you see that every day Men make Glass, and other Diaphanous Bodies not much inferior in beauty to the fairest Gems?  B. 
It is one thing to make one Transparent of many by mixture, and another to make Transparent of not Transparent. Any very hard Stone, if it be beaten into small Sands, such as is used for Hour-Glasses, every one of those Sands, if you look upon it with a Microscope, you will find to be Transparent; and the harder and whiter the Sun is, so much the more Transparent, as I have seen in the Stone of which are made Millstones, which Stone is here called Greet. And I doubt not but the Sands of white Marble must be more Transparent. But there are no Sands so Transparent that they have not a scurf upon them as hard, perhaps, as the Stone itself; which they whose profession it is to make Glass, have the Art to scour and wash away. And therefore I think it no great wonder to bring those Sands into one Lump, though I know not how they do it.  A. 
I know they do it with Lie made with a Salt extracted from the Ashes of an Herb, of which Salt they make a strong Lie, and mingle it with the Sand, and then bake it.  B. 
Like enough. But still it is a Compound of two Transparent Bodies, whereof one is the Natural Stone, the other is the Mortar. This therefore doth not prove, that one and the same Body, of not Transparent can be made Transparent.  A. 
Since they can make one Transparent Body of many, why do they not of a great many small sparks of natural Diamant compound one great one? It would bear the charges of all the Materials, and beside, every them.  B. 
'Tis probable it would. But it may be they know no Salt that howsoever prepared, which (with how great a Fire soever) can make them melt. And, it may be the true Crystal of the Mountain, which is found in great pieces in the Alps, is but a compound of many small ones, and made by the Earth's Annual Motion. For it is a very swift Motion. Suppose now that within a very small Cavern of those Rocks whose smallest Atoms are Crystal, and the Cavity filled with Air; and consider what a tumult would be made by the swift reciprocation of that Air; whether it would not in time separate those Atoms from the Rock, and jumbling them together make them rub off their scruf from one another, and by little and little to touch one another in polished plains, and consequently stick together, till in length of time they become one lump of clean Crystal.  A. 
I believe that the least parts of created substances lay mingled together at first, till it pleased God to separate all dissimilar natures, and congregate the similar, to which this Annual Motion is proper. But they say that Crystal is found in the open Air hanging like Icicles upon the Rocks. Which (if true) defeats this supposition of a narrow Cavern. And therefore I must have some further experience of it before I make it my opinion. But howsoever, it still holds true that Diaphanous Bodies of all sorts, in their least parts, were made by God in the beginning of the World. But it may be true, notwithstanding those Icicles. For the force of the Air that could break off those Diaphanous Atoms in a Cavern, can do the same in the open Air. And I know that a less force of Air can break some Bodies into small pieces, not much less hard than Chystal, by corrupting them.  B. 
That which you now have said is somewhat. But I deny not the possibility, but only doubt of the Operation. You may therefore pass to some other Question.  A. 
Well, I will ask you then a Question about Refraction. I know already that for the Cause of Refraction (when the Light falleth through a thinner Medium upon a thicker) you assign the resistance of the thicker Body; but you do not mean there by Rarum and Densum, two Bodies whereof in equal spaces one has more substance in it than the other.  B. 
No. For equal spaces contain equal Bodies. But I mean by Densum any Body which more resisteth the Motion of the Air, and by Rarum that which resisteth less.  A. 
But you have not declared in what that resistance consisteth.  B. 
I suppose it proceedeth from the Hardness.  A. 
But from thence it will follow, that all Transparent Bodies that equally refract are equally Hard. Which I think is not true, because the Refraction of Glass is not greater (at least in comparison of their Hardnesses) than that of Water.  B. 
I confess it. Therefore I think we must take in Gravity to a Share in the production of this Refraction. For I never considered Refraction but in Glass; because my business then was only to find the Causes of the Phaenomena of Telescopes and Microscopes. Let therefore A B (in Fig. 7.) be a hard, and consequently, a heavy Body. And from above (as from the Sun) let C A be the line of Incidence, and produced to D. And draw A E perpendicular to A B. It is manifest that the Hardness in A B shall turn the stream of the Light inwards toward A E, suppose in the line A e. It is also evident that the Endeavour in B, which is (being heavy) downward, shall turn the stream again inward, towards A E as in A b. Thus it is in Refraction from the Sun downwards. In like manner, if the light come from below, as from a Candle in the point D, the line of Incidence will be D A, and produced will pass to C. And the resistance of the Hardness in A will turn the stream A C inward, suppose into B l, and make C l equal to D e. For passing into a thinner Medium, it will depart from the perpendicular in an Angle equal to the Angle D A e, by which it came nearer to it in A e. So also the resistance of the Gravity in the point A shall turn the stream of the Light into the line A i, and make the Angle l A i equal to the Angle e A b. And thus you see in what manner, though not in what proportion Hardness and Gravity conjoin their resistance in the Causing of Refraction.  A. 
But you proved yesterday, that a heavy Body does not Gravitate upon a Body equally heavy. Now this A B has upper parts, and lower parts; and if the upper parts do not Gravitate upon the lower parts, how can there be any Endeavour at all downward to contribute to the Refraction?  B. 
I told you yesterday, that when a heavy Body was set upon another Body heavier or harder than itself, the Endeavour of it downward was diverted another way, but not that it was extinguished. But in this case, where it lieth upon Air, the first endeavour of the lowest part worketh downward. For neither Motion nor Body can be utterly extinguished by a less than an Omnipotent power. All Bodies as long as they are Bodies, are in Motion one way or other, though the farther it be communicated, so much the less.  A. 
But since you hold that Motion is propagated through all Bodies, how hard or heavy soever they be, I see no Cause but that all Bodies should be Transparent.  B. 
There are divers Causes that take away Transparency. First, if the Body be not perfectly Homogeneous, that is to say, if the smallest parts of it be not all precisely of the same nature, or do not so touch one another as to leave no Vacuum within it; or though they touch, if they be not as hard in the contact as in any other line. For then the Refractions will be so changed both in their direction, and in their strength, as that no Light shall come through it to the Eye; as in Wood and ordinary Stone and Metal. Secondly, The Gravity and hardness may be so great, as to make the Angle refracted so great, as the second Refraction shall not direct the beam of light to the Eye; as if the Angle of Refraction were D A E, the Refracted line would be perpendicular to A B, and never come to the line A D, in which is the Eye.  A. 
To know how much of the Refraction is due to the Hardness, and how much to the Gravity, I believe it is impossible, though the Quantity of the whole be easily measured in a Diaphanous Body given. And both you and Mr. Warner have demonstrated, that as the Sine of the Angle Refracted in one Inclination is to the Sine of the Angle Refracted in another Inclination, so is the Sine of one Inclination to the Sine of the Angle of the other Inclination. Which Demonstrations are both published by Mersennus in the end of the first Volume of his Cogitata Physico-Mathematica. But since there be many Bodies, through which though there pass Light enough, yet no Object appears through them to the Eye, what is the reason of that?  B. 
You mean Paper. For Paper-Windows will enlighten a Room, and yet not show the Image of an Object without the Room. But 'tis because there are in Paper abundance of pores, through which the Air passing moveth the Air within; by the Reflections whereof any thing within may be seen. And in the same Paper there are again as many parts not Transparent, through which the Air cannot pass, but must be reflected first to all parts of the Object, and from them again to the Paper; and at the Paper either reflected again or transmitted, according as it falls upon Pores or not Pores; so that the Light from the Object can never come together at the Eye.  A. 
There belongs yet to this Subject the Causes of the diversity of Colours. But I am so well satisfied with that which you have written of it in the 24th Chapter of your Book de Corpore, that I need not trouble you further in it. And now I have but one Question more to ask you, which I thought upon last night. I have read in an ancient Historian that Living Creatures after a great deluge were produced by the Earth, which being then very soft, there were bred in it (it may be by the rapid Motion of the Sun) many Blisters, which in time breaking, brought forth (like so many Eggs) all manner of living Creatures great and small, which since it is grown hard it cannot do. What think you of it?  B. 
It is true that the Earth produced the first living Creatures of all sorts but Man. For God said, (Gen. 1. vers. 24.) Let the Earth produce every living Creature, Cattle, and creeping thing, etc. But then again (ver. 25.) it is said that God made the Beast of the Earth, etc. So that it is evident that God gave unto the Earth that virtue. Which virtue must needs consist in Motion, because all Generation is Motion. But Man, though the same day, was made afterward.  A. 
Why hath not the Earth the same virtue now? Is not the Sun the same it was? Or is there no Earth now soft enough?  B. 
Yes. And it may be the Earth may yet produce some very small Living Creatures: And perhaps Male and Female. For the smallest Creatures which we take notice of, do engender, though they do not all by conjunction; therefore if the Earth produce living Creatures at this day, God did not absolutely rest from all his Works on the seventh day, but (as it is Cap. 2. ver. 2.) he rested from all the work he had made. And therefore it is no harm to think that God worketh still, and when and where and what he pleaseth. Beside, 'tis very hard to believe, that to produce Male and Female, and all that belongs thereto, as also the several and curious Organs of Sense and Memory, could be the work of any thing that had not understanding. From whence, I think we may conclude, that whatsoever was made after the Creation, was a new Creature made by God no therwise than the first Creatures were, excepting only Man.  A. 
They are then in an Error that think there are no more different kinds of Animals in the World now, than there were in the Ark of Noah.  B. 
Yes doubtless. For they have no Text of Scripture from which it can be proved.  A. 
The Questions of Nature which I could yet propound are innumerable. And since I cannot go through them, I must give over somewhere, and why not here? For I have troubled you enough, though I hope you will forgive me.  B. 
So God forgive us both as we do one another. But forget not to take with you the Demonstration of a strait Line equal to an Arc of a Circle.  
FINIS.