Discourse on Floating Bodies Part 8

Whether Figure have any influence upon the encrease or diminution of the Resistance in any Weight against its being raised in the Air[78]; and I suppose, that I am to maintain the Affirmative, a.s.serting that a Ma.s.s of Lead, reduced to the Figure of a Ball, shall be raised with less force, then if the same had been made into a thinne and broad Plate, because that it in this s.p.a.cious Figure, hath a great quant.i.ty of Air to penetrate, and in that other, more compacted and contracted very little: and to demonstrate the truth of such my Opinion, I will hang in a small thred first the Ball or Bullet, and put that into the water, tying the thred that upholds it to one end of the Ballance that I hold in the Air, and to the other end I by degrees adde so much Weight, till that at last it brings up the Ball of Lead out of the water: to do which, suppose a Gravity of thirty Ounces sufficeth; I afterwards reduce the said Lead into a flat and thinne Plate, the which I likewise put into the water, suspended by three threds, which hold it parallel to the Surface of the water, and putting in the same manner, Weights to the other end, till such time as the Plate comes to be raised and drawn out of the water: I finde that thirty six ounces will not suffice to seperate it from the water, and raise it thorow the Air: and arguing from this Experiment, I affirm, that I have fully demonstrated the truth of my Proposition. Here my Oponents desires me to look down, shewing me a thing which I had not before observed, to wit, that in the Ascent of the Plate out of the water, it draws after it another Plate (_if I may so call it_) of water, which before it divides and parts from the inferiour Surface of the Plate of Lead, is raised above the Levell of the other water, more than the thickness of the back of a Knife: Then he goeth to repeat the Experiment with the Ball, and makes me see, that it is but a very small quant.i.ty of water, which cleaves to its compacted and contracted Figure: and then he subjoynes, that its no wonder, if in seperating the thinne and broad Plate from the water, we meet with much greater Resistance, than in seperating the Ball, since together with the Plate, we are to raise a great quant.i.ty of water, which occurreth not in the Ball: He telleth me moreover, how that our Question is, whether the Resistance of Elevation be greater in a dilated Plate of Lead, than in a Ball, and not whether more resisteth a Plate of Lead with a great quant.i.ty of water, or a Ball with a very little water: He sheweth me in the close, that the putting the Plate and the Ball first into the water, to make proofe thereby of their Resistance in the Air, is besides our case, which treats of Elivating in the Air, and of things placed in the Air, and not of the Resistance that is made in the Confines of the Air and water, and by things which are part in Air and part in water: and lastly, they make me feel with my hand, that when the thinne Plate is in the Air, and free from the weight of the water, it is raised with the very same Force that raiseth the Ball. Seeing, and understanding these things, I know not what to do, unless to grant my self convinced, and to thank such a Friend, for having made me to see that which I never till then observed: and, being advertised by this same Accident, to tell my Adversaries, that our Question is, whether a Board and a Ball of Ebony, equally go to the bottom in water, and not a Ball of Ebony and a Board of Ebony, joyned with another flat Body of Air: and, farthermore, that we speak of sinking, and not sinking to the bottom, in water, and not of that which happeneth in the Confines of the water and Air to Bodies that be part in the Air, and part in the water; nor much less do we treat of the greater or lesser Force requisite in seperating this or that Body from the Air; not omitting to tell them, in the last place, that the Air doth resist, and gravitate downwards in the water, just so much as the water (if I may so speak) gravitates and resists upwards in the Air, and that the same Force is required to sinke a Bladder under water, that is full of Air, as to raise it in the Air, being full of water, removing the consideration of the weight of that Filme or Skinne, and considering the water and the Air only. And it is likewise true, that the same Force is required to sink a Cup or such like Vessell under water, whilst it is full of Air, as to raise it above the Superficies of the water, keeping it with the mouth downwards; whilst it is full of water, which is constrained in the same manner to follow the Cup which contains it, and to rise above the other water into the Region of the Air, as the Air is forced to follow the same Vessell under the Surface of the water, till that in this c{a}se the water, surmounting the brimme of the Cup, breaks in, driving thence the Air, and in that case, the said brimme coming out of the water, and arriving to the Confines of the Air, the water falls down, and the Air sub-enters to fill the cavity of the Cup: upon which ensues, that he no less transgresses the Articles of the _Convention_, who produceth a Plate conjoyned with much Air, to see if it descend to the bottom in water, then he that makes proof of the Resistance against Elevation in Air with a Plate of Lead, joyned with a like quant.i.ty of water.

[78] An Experiment of the operation of Figures, in encreasing or lessening of the Airs Resistance of Division.

[Sidenote: _Aristotles_ opinion touching the Operation of Figure examined.]

I have said all that I could at present think of, to maintain the a.s.sertion I have undertook. It remains, that I examine that which _Aristotle_ hath writ of this matter towards the end of his Book De Caelo[79]; wherein I shall note two things: the one that it being true as hath been demonstrated, that Figure hath nothing to do about the moving or not moving it self upwards or downwards, its seemes that _Aristotle_ at his first falling upon this Speculation, was of the same opinion, as in my opinion may be collected from the examination of his words. 'Tis true, indeed, that in essaying afterwards to render a reason of such effect, as not having in my conceit hit upon the right, (which in the second place I will examine) it seems that he is brought to admit the largenesse of Figure, to be interessed in this operation. As to the first particuler, hear the precise words of _Aristotle_.

[79] _Aristot. de Caelo_ Lib. 4. Cap 6.

_Figures are not the Causes of moving simply upwards or downwards, but of moving more slowly or swiftly[80][81], and by what means this comes to pa.s.s, it is not difficult to see._

[80] _Aristotle_ makes not Figure the cause of Motion absolutely, but of swift or slow motion,

[81] Lib. 4. Cap. 6: Text. 42.

Here first I note, that the terms being four, which fall under the present consideration, namely, Motion, Rest, Slowly and Swiftly: And _Aristotle_ naming figures as Causes of Tardity and Velocity, excluding them from being the Cause of absolute and simple Motion, it seems necessary, that he exclude them on the other side, from being the Cause of Rest, so that his meaning is this. Figures are not the Causes of moving or not moving absolutely, but of moving quickly or slowly: and, here, if any should say the mind of _Aristotle_ is to exclude Figures from being Causes of Motion, but yet not from being Causes of Rest, so that the sence would be to remove from Figures, there being the Causes of moving simply, but yet not there being Causes of Rest, I would demand, whether we ought with _Aristotle_ to understand, that all Figures universally, are, in some manner, the causes of Rest in those Bodies, which otherwise would move, or else some particular Figures only, as for Example, broad and thinne Figures: If all indifferently, then every Body shall rest: because every Body hath some Figure, which is false; but if some particular Figures only may be in some manner a Cause of Rest, as, for Example, the broad, then the others would be in some manner the Causes of Motion: for if from seeing some Bodies of a contracted Figure move, which after dilated into Plates rest, may be inferred, that the Amplitude of Figure hath a part in the Cause of that Rest; so from seeing such like Figures rest, which afterwards contracted move, it may with the same reason be affirmed, that the united and contracted Figure, hath a part in causing Motion, as the remover of that which impeded it: The which again is directly opposite to what _Aristotle_ saith, namely, that Figures are not the Causes of Motion. Besides, if _Aristotle_ had admitted and not excluded Figures from being Causes of not moving in some Bodies, which moulded into another Figure would move, he would have impertinently propounded in a dubitative manner, in the words immediately following, whence it is, that the large and thinne Plates of Lead or Iron, rest upon the water, since the Cause was apparent, namely, the Amplitude of Figure. Let us conclude, therefore, that the meaning of _Aristotle_ in this place is to affirm, that Figures are not the Causes of absolutely moving or not moving, but only of moving swiftly or slowly: which we ought the rather to believe, in regard it is indeed a most true conceipt and opinion. Now the mind of _Aristotle_ being such, and appearing by consequence, rather contrary at the first sight, then favourable to the a.s.sertion of the Oponents, it is necessary, that their Interpretation be not exactly the same with that, but such, as being in part understood by some of them, and in part by others, was set down: and it may easily be indeed so, being an Interpretation consonent to the sence of the more famous Interpretors, which is, that the Adverbe _Simply_ or _Absolutely_, put in the Text, ought not to be joyned to the Verbe to _Move_, but with the Noun _Causes_: so that the purport of _Aristotles_ words, is to affirm, That Figures are not the Causes absolutely of moving or not moving, but yet are Causes _Secundum quid_, _viz._ in some sort; by which means, they are called Auxiliary and Concomitant Causes: and this Proposition is received and a.s.serted as true by _Signor Buonamico Lib. 5. Cap. 28._ where he thus writes.

_There are other Causes concomitant, by which some things float, and others sink, among which the Figures of Bodies hath the first place_, &c.

Concerning this Proposition, I meet with many doubts and difficulties, for which me thinks the words of _Aristotle_ are not capable of such a construction and sence, and the difficulties are these.

First in the order and disposure of the words of _Aristotle_, the particle _Simpliciter_, or if you will _absolute_, is conjoyned with the Verb _to move_, and seperated from the Noun _Causes_, the which is a great presumption in my favour, seeing that the writing and the Text saith, Figures are not the Cause of moving simply upwards or downwards, but of quicker or slower Motion: and, saith not, Figures are not simply the Causes of moving upwards or downwards, and when the words of a Text receive, transposed, a sence different from that which they sound, taken in the order wherein the Author disposeth them, it is not convenient to inverte them. And who will affirm that _Aristotle_ desiring to write a Proposition, would dispose the words in such sort, that they should import a different, nay, a contrary sence? contrary, I say, because understood as they are written; they say, that Figures are not the Causes of Motion, but inverted, they say, that Figures are the Causes of Motion, &c.

Moreover, if the intent of _Aristotle_ had been to say, that Figures are not simply the Causes of moving upwards or downwards, but only Causes _Secundum quid_, he would not have adjoyned those words, _but they are Causes of the more swift or slow Motion_; yea, the subjoining this would have been not only superfluous but false, for that the whole tenour of the Proposition would import thus much. Figures are not the absolute Causes of moving upwards or downwards, but are the absolute Cause of the swift or slow Motion; which is not true: because the primary Causes of greater or lesser Velocity, are by _Aristotle_ in the 4th of his _Physicks_, _Text. 71._ attributed to the greater or lesser Gravity of Moveables, compared among themselves, and to the greater or lesser Resistance of the _Medium's_, depending on their greater or less Cra.s.situde: and these are inserted by _Aristotle_ as the primary Causes; and these two only are in that place nominated: and Figure comes afterwards to be considered, _Text. 74._ rather as an Instrumentall Cause of the force of the Gravity, the which divides either with the Figure, or with the _Impetus_; and, indeed, Figure by it self without the force of Gravity or Levity, would opperate nothing.

I adde, that if _Aristotle_ had an opinion that Figure had been in some sort the Cause of moving or not moving, the inquisition which he makes immediately in a doubtfull manner, whence it comes, that a Plate of Lead flotes, would have been impertinent; for if but just before he had said, that Figure was in a certain sort the Cause of moving or not moving, he needed not to call in Question, by what Cause the Plate of Lead swims, and then ascribing the Cause to its Figure; and framing a discourse in this manner. Figure is a Cause _Secundum quid_ of not sinking: but, now, if it be doubted, for what Cause a thin Plate of Lead goes not to the bottom; it shall be answered, that that proceeds from its Figure: a discourse which would be indecent in a Child, much more in _Aristotle_; For where is the occasion of doubting? And who sees not, that if _Aristotle_ had held, that Figure was in some sort a Cause of Natation, he would without the least Hesitation have writ; That Figure is in a certain sort the Cause of Natation, and therefore the Plate of Lead in respect of its large and expatiated Figure swims; but if we take the proposition of _Aristotle_ as I say, and as it is written, and as indeed it is true, the ensuing words come in very oppositely, as well in the introduction of swift and slow, as in the question, which very pertinently offers it self, and would say thus much.

Figures are not the Cause of moving or not moving simply upwards or downwards, but of moving more quickly or slowly: But if it be so, the Cause is doubtfull, whence it proceeds, that a Plate of Lead or of Iron broad and thin doth swim, &c. And the occasion of the doubt is obvious, because it seems at the first glance, that the Figure is the Cause of this Natation, since the same Lead, or a less quant.i.ty, but in another Figure, goes to the bottom, and we have already affirmed, that the Figure hath no share in this effect.

Lastly, if the intent of _Aristotle_ in this place had been to say, that Figures, although not absolutely, are at least in some measure the Cause of moving or not moving: I would have it considered, that he names no less the Motion upwards, than the other downwards: and because in exemplifying it afterwards, he produceth no other Experiments than of a Plate of Lead, and Board of Ebony, Matters that of their own Nature go to the bottom, but by vertue (as our Adversaries say) of their Figure, rest afloat; it is fit that they should produce some other Experiment of those Matters, which by their Nature swims, but retained by their Figure rest at the bottom. But since this is impossible to be done, we conclude, that _Aristotle_ in this place, hath not attributed any action to the Figure of simply moving or not moving.

But though he hath exquisitely Philosophiz'd, in investigating the solution of the doubts he proposeth, yet will I not undertake to maintain, rather various difficulties, that present themselves unto me, give me occasion of suspecting that he hath not entirely displaid unto us, the true Cause of the present Conclusion: which difficulties I will propound one by one, ready to change opinion, whenever I am shewed, that the Truth is different from what I say; to the confession whereof I am much more inclinable than to contradiction.

[Sidenote: _Aristotle_ erred in affirming a Needle dimitted long wayes to sink.]

_Aristotle_ having propounded the Question, whence it proceeds, that broad Plates of Iron or Lead, float or swim; he addeth (as it were strengthening the occasion of doubting) forasmuch as other things, less, and less grave, be they round or long, as for instance a Needle go to the bottom. Now I here doubt, or rather am certain that a Needle put lightly upon the water, rests afloat, no less than the thin Plates of Iron or Lead. I cannot believe, albeit it hath been told me, that some to defend _Aristotle_ should say, that he intends a Needle demitted not longwayes but endwayes, and with the Point downwards; nevertheless, not to leave them so much as this, though very weak refuge, and which in my judgement _Aristotle_ himself would refuse, I say it ought to be understood, that the Needle must be demitted, according to the Dimension named by _Aristotle_, which is the length: because, if any other Dimension than that which is named, might or ought to be taken, I would say, that even the Plates of Iron and Lead, sink to the bottom, if they be put into the water edgewayes and not flatwayes. But because _Aristotle_ saith, broad Figures go not to the bottom, it is to be understood, being demitted broadwayes: and, therefore, when he saith, long Figures as a Needle, albeit light, rest not afloat, it ought to be understood of them when demitted longwayes.

_Moreover, to say that_ Aristotle _is to be understood of the Needle demitted with the Point downwards, is to father upon him a great impertinency; for in this place he saith, that little Particles of Lead or Iron, if they be round or long as a Needle, do sink to the bottome; so that by his Opinion, a Particle or small Grain of Iron cannot swim: and if he thus believed, what a great folly would it be to subjoyn, that neither would a Needle demitted endwayes swim? And what other is such a Needle, but many such like Graines acc.u.mulated one upon another? It was too unworthy of such a man to say, that one single Grain of Iron could not swim, and that neither can it swim, though you put a hundred more upon it._

Lastly, either _Aristotle_ believed, that a Needle demitted longwayes upon the water, would swim, or he believed that it would not swim: If he believed it would not swim, he might well speak as indeed he did; but if he believed and knew that it would float, why, together with the dubious Problem of the Natation of broad Figures, though of ponderous Matter, hath he not also introduced the Question; whence it proceeds, that even long and slender Figures, howbeit of Iron or Lead do swim? And the rather, for that the occasion of doubting seems greater in long and narrow Figures, than in broad and thin, as from _Aristotles_ not having doubted of it, is manifested.

No lesser an inconvenience would they fasten upon _Aristotle_, who in his defence should say, that he means a Needle pretty thick, and not a small one; for take it for granted to be intended of a small one; and it shall suffice to reply, that he believed that it would swim; and I will again charge him with having avoided a more wonderfull and intricate Probleme, and introduced the more facile and less wonderfull.

We say freely therefore, that _Aristotle_ did hold, that only the broad Figure did swim, but the long and slender, such as a Needle, not. The which nevertheless is false, as it is also false in round Bodies: because, as from what hath been predemonstrated, may be gathered, little b.a.l.l.s of Lead and Iron, do in like manner swim.

[Sidenote: _Aristotle_ affirmeth some Bodies volatile for their Minuity, Text. 42.]

He proposeth likewise another Conclusion, which likewise seems different from the truth, and it is, That some things, by reason of their littleness fly in the Air, as the small dust of the Earth, and the thin leaves of beaten Gold: but in my Opinion, Experience shews us, that that happens not only in the Air, but also in the water, in which do descend, even those Particles or Atomes of Earth, that disturbe it, whose minuity is such, that they are not deservable, save only when they are many hundreds together. Therefore, the dust of the Earth, and beaten Gold, do not any way sustain themselves in the Air, but descend downwards, and only fly to and again in the same, when strong Windes raise them, or other agitations of the Air commove them: and this also happens in the commotion of the water, which raiseth its Sand from the bottom, and makes it muddy. But _Aristotle_ cannot mean this impediment of the commotion, of which he makes no mention, nor names other than the lightness of such Minutiae or Atomes, and the Resistance of the Cra.s.situdes of the Water and Air, by which we see, that he speakes of a calme, and not disturbed and agitated Air: but in that case, neither Gold nor Earth, be they never so small, are sustained, but speedily descend.

[Sidenote: _Democritus_ placed the Cause of Natation in certain fiery Atomes.]

He pa.s.seth next to confute _Democritus_[82], which, by his Testimony would have it, that some Fiery Atomes, which continually ascend through the water, do spring upwards, and sustain those grave Bodies, which are very broad, and that the narrow descend to the bottom, for that but a small quant.i.ty of those Atomes, encounter and resist them.

[82] _Aristot. De Caelo_ lib. 4. cap. 6. text. 43.

I say, _Aristotle_ confutes this position[83], saying, that that should much more occurre in the Air, as the same _Democritus_ instances against himself, but after he had moved the objection, he slightly resolves it, with saying, that those Corpuscles which ascend in the Air, make not their _Impetus_ conjunctly. Here I will not say, that the reason alledged by _Democritus_ is true[84], but I will only say, it seems in my judgement, that it is not wholly confuted by _Aristotle_, whilst he saith, that were it true, that the calid ascending Atomes, should sustain Bodies grave, but very broad, it would much more be done in the Air, than in Water, for that haply in the Opinion of _Aristotle_, the said calid Atomes ascend with much greater Force and Velocity through the Air, than through the water. And if this be so, as I verily believe it is, the Objection of _Aristotle_ in my judgement seems to give occasion of suspecting, that he may possibly be deceived in more than one particular: First, because those calid Atomes, (whether they be Fiery Corpuscles, or whether they be Exhalations, or in short, whatever other matter they be, that ascends upwards through the Air) cannot be believed to mount faster through Air, than through water: but rather on the contrary, they peradventure move more impetuously through the water, than through the Air, as hath been in part demonstrated above. And here I cannot finde the reason, why _Aristotle_ seeing, that the descending Motion of the same Moveable, is more swift in Air, than in water, hath not advertised us, that from the contrary Motion, the contrary should necessarily follow; to wit, that it is more swift in the water, than in the Air: for since that the Moveable which descendeth, moves swifter through the Air, than through the water, if we should suppose its Gravity gradually to diminish, it would first become such, that descending swiftly through the Air, it would descend but slowly through the water: and then again, it might be such, that descending in the Air, it should ascend in the water: and being made yet less grave, it shall ascend swiftly through the water, and yet descend likewise through the Air: and in short, before it can begin to ascend, though but slowly through the Air, it shall ascend swiftly through the water: how then is it true, that ascending Moveables move swifter through the Air, than through the water?

[83] _Democritus_ confuted by _Aristotle_, text 43.

[84] _Aristotles_ confutation of _Democritus_ refuted by the Author.

That which hath made _Aristotle_ believe, the Motion of Ascent to be swifter in Air, than in water, was first, the having referred the Causes of slow and quick, as well in the Motion of Ascent, as of Descent, only to the diversity of the Figures of the Moveable, and to the more or less Resistance of the greater or lesser Cra.s.situde, or Rarity of the _Medium_; not regarding the comparison of the Excesses of the Gravities of the Moveables, and of the _Mediums_: the which notwithstanding, is the most princ.i.p.al point in this affair: for if the augmentation and diminution of the Tardity or Velocity, should have only respect to the Density or Rarity of the _Medium_, every Body that descends in Air, would descend in water: because whatever difference is found between the Cra.s.situde of the water, and that of the Air, may well be found between the Velocity of the same Moveable in the Air, and some other Velocity: and this should be its proper Velocity in the water, which is absolutely false. The other occasion is, that he did believe, that like as there is a positive and intrinsecall Quality, whereby Elementary Bodies have a propension of moving towards the Centre of the Earth, so there is another likewise intrinsecall[85], whereby some of those Bodies have an _Impetus_ of flying the Centre, and moving upwards: by Vertue of which intrinsecall Principle, called by him Levity, the Moveables which have that same Motion more easily penetrate the more subtle _Medium_, than the more dense: but such a Proposition appears likewise uncertain, as I have above hinted in part, and as with Reasons and Experiments, I could demonstrate, did not the present Argument importune me, or could I dispatch it in few words.

[85] Lib. 4. Cap. 5.

The Objection therefore of _Aristotle_ against _Democritus_, whilst he saith, that if the Fiery ascending Atomes should sustain Bodies grave, but of a distended Figure, it would be more observable in the Air than in the water, because such Corpuscles move swifter in that, than in this, is not good; yea the contrary would evene, for that they ascend more slowly through the Air: and, besides their moving slowly, they ascend, not united together, as in the water, but discontinue, and, as we say, scatter: And, therefore, as _Democritus_ well replyes, resolving the instance they make not their push or _Impetus_ conjunctly.

_Aristotle_, in the second place, deceives himself, whilst he will have the said grave Bodies to be more easily sustained by the said Fiery ascending Atomes in the Air than in the Water: not observing, that the said Bodies are much more grave in that, than in this, and that such a Body weighs ten pounds in the Air, which will not in the water weigh 1/2 an ounce; how can it then be more easily sustained in the Air, than in the Water?

[Sidenote: _Democritus_ confuted by the Authour.]

Let us conclude, therefore, that _Democritus_ hath in this particular better Philosophated than _Aristotle_. But yet will not I affirm, that _Democritus_ hath reason'd rightly, but I rather say, that there is a manifest Experiment that overthrows his Reason, and this it is, That if it were true, that calid ascending Atomes should uphold a Body, that if they did not hinder, would go to the bottom, it would follow, that we may find a Matter very little superiour in Gravity to the water, the which being reduced into a Ball, or other contracted Figure, should go to the bottom, as encountring but few Fiery Atomes; and which being distended afterwards into a dilated and thin Plate, should come to be thrust upwards by the impulsion of a great Mult.i.tude of those Corpuscles, and at last carried to the very Surface of the water: which wee see not to happen; Experience shewing us, that a Body _v. gra._ of a Sphericall Figure, which very hardly, and with very great leasure goeth to the bottom, will rest there, and will also descend thither, being reduced into whatsoever other distended Figure.

We must needs say then, either that in the water, there are no such ascending Fiery Atoms, or if that such there be, that they are not able to raise and lift up any Plate of a Matter, that without them would go to the bottom: Of which two Positions, I esteem the second to be true, understanding it of water, const.i.tuted in its naturall Coldness. But if we take a Vessel of Gla.s.s, or Bra.s.s, or any other hard matter, full of cold water, within which is put a Solid of a flat or concave Figure, but that in Gravity exceeds the water so little, that it goes slowly to the bottom; I say, that putting some burning Coals under the said Vessel, as soon as the new Fiery Atomes shall have penetrated the substance of the Vessel, they shall without doubt, ascend through that of the water, and thrusting against the foresaid Solid, they shall drive it to the Superficies, and there detain it, as long as the incursions of the said Corpuscles shall last, which ceasing after the removall of the Fire, the Solid being abandoned by its supporters, shall return to the bottom.

But _Democritus_ notes, that this Cause only takes place when we treat of raising and sustaining of Plates of Matters, but very little heavier than the water, or extreamly thin: but in Matters very grave, and of some thickness, as Plates of Lead or other Mettal, that same Effect wholly ceaseth: In Testimony of which, let's observe that such Plates, being raised by the Fiery Atomes, ascend through all the depth of the water, and stop at the Confines of the Air, still staying under water: but the Plates of the Opponents stay not, but only when they have their upper Superficies dry, nor is there any means to be used, that when they are within the water, they may not sink to the bottom.

The cause, therefore, of the Supernatation of the things of which _Democritus_ speaks is one, and that of the Supernatation of the things of which we speak is another. But, returning to _Aristotle_[86], methinks that he hath more weakly confuted _Democritus_, than _Democritus_ himself hath done: For _Aristotle_ having propounded the Objection which he maketh against him, and opposed him with saying, that if the calid ascendent Corpuscles were those that raised the thin Plate, much more then would such a Solid be raised and born upwards through the Air, it sheweth that the desire in _Aristotle_ to detect _Democritus_, was predominate over the exquisiteness of Solid Philosophizing: which desire of his he hath discovered in other occasions, and that we may not digress too far from this place, in the Text precedent to this Chapter which we have in hand[87]; where he attempts to confute the same _Democritus_ for that he, not contenting himself with names only, had essayed more particularly to declare what things Gravity and Levity were; that is, the Causes of descending and ascending, (and had introduced Repletion and Vacuity) ascribing this to Fire, by which it moves upwards, and that to the Earth, by which it descends; afterwards attributing to the Air more of Fire, and to the water more of Earth. But _Aristotle_ desiring a positive Cause, even of ascending Motion, and not as _Plato_, or these others, a simple negation, or privation, such as Vacuity would be in reference to Repletion[88], argueth against _Democritus_ and saith: If it be true, as you suppose, then there shall be a great Ma.s.s of water, which shall have more of Fire, than a small Ma.s.s of Air, and a great Ma.s.s of Air, which shall have more of Earth than a little Ma.s.s of water, whereby it would ensue, that a great Ma.s.s of Air, should come more swiftly downwards, than a little quant.i.ty of water: But that is never in any case soever: Therefore _Democritus_ discourseth erroneously.

[86] _Aristotle_ shews his desire of finding _Democritus_ in an Error, to exceed that of discovering Truth.

[87] Cap. 5. Text 41.

[88] Id. ibid.

But in my opinion, the Doctrine of _Democritus_ is not by this allegation overthrown, but if I erre not, the manner of _Aristotle_ deduction either concludes not, or if it do conclude any thing, it may with equall force be restored against himself. _Democritus_ will grant to _Aristotle_, that there may be a great Ma.s.s of Air taken, which contains more Earth, than a small quant.i.ty of water, but yet will deny, that such a Ma.s.s of Air, shall go faster downwards than a little water, and that for many reasons. First, because if the greater quant.i.ty of Earth, contained in the great Ma.s.s of Air, ought to cause a greater Velocity than a less quant.i.ty of Earth, contained in a little quant.i.ty of water, it would be necessary, first, that it were true, that a greater Ma.s.s of pure Earth, should move more swiftly than a less: But this is false, though _Aristotle_ in many places affirms it to be true: because not the greater absolute, but the greater specificall Gravity, is the cause of greater Velocity[89]: nor doth a Ball of Wood, weighing ten pounds, descend more swiftly than one weighing ten Ounces, and that is of the same Matter: but indeed a Bullet of Lead of four Ounces, descendeth more swiftly than a Ball of Wood of twenty Pounds: because the Lead is more _grave in specie_ than the Wood. Therefore, its not necessary, that a great Ma.s.s of Air, by reason of the much Earth contained in it, do descend more swiftly than a little Ma.s.s of water[90], but on the contrary, any whatsoever Ma.s.s of water, shall move more swiftly than any other of Air, by reason the partic.i.p.ation of the terrene parts _in specie_ is greater in the water, than in the Air. Let us note, in the second place, how that in multiplying the Ma.s.s of the Air, we not only multiply that which is therein of terrene, but its Fire also: whence the Cause of ascending, no less encreaseth, by vertue of the Fire, than that of descending on the account of its multiplied Earth. It was requisite in increasing the greatness of the Air, to multiply that which it hath of terrene only, leaving its Fire in its first state, for then the terrene parts of the augmented Air, overcoming the terrene parts of the small quant.i.ty of water, it might with more probability have been pretended, that the great quant.i.ty of Air, ought to descend with a greater _Impetus_, than the little quant.i.ty of water.

[89] The greater Specificall, not the greater absolute Gravity, is the Cause of Velocity.

[90] Any Ma.s.s of water shal move more swiftly, than any of Air, and why.

Therefore, the Fallacy lyes more in the Discourse of _Aristotle_, than in that of _Democritus_, who with severall other Reasons might oppose _Aristotle_, and alledge; If it be true, that the extreame Elements be one simply grave, and the other simply light, and that the mean Elements partic.i.p.ate of the one, and of the other Nature; but the Air more of Levity, and the water more of Gravity, then there shall be a great Ma.s.s of Air, whose Gravity shall exceed the Gravity of a little quant.i.ty of water, and therefore such a Ma.s.s of Air shall descend more swiftly than that little water: But that is never seen to occurr: Therefore its not true, that the mean Elements do partic.i.p.ate of the one, and the other quality. This argument is fallacious, no less than the other against _Democritus_.

Lastly, _Aristotle_ having said, that if the Position of _Democritus_ were true, it would follow, that a great Ma.s.s of Air should move more swiftly than a small Ma.s.s of water, and afterwards subjoyned, that that is never seen in any Case: methinks others may become desirous to know of him in what place this should evene, which he deduceth against _Democritus_, and what Experiment teacheth us, that it never falls out so. To suppose to see it in the Element of water, or in that of the Air is vain, because neither doth water through water, nor Air through Air move, nor would they ever by any whatever partic.i.p.ation others a.s.sign them, of Earth or of Fire: the Earth, in that it is not a Body fluid, and yielding to the mobility of other Bodies, is a most improper place and _Medium_ for such an Experiment: _Vacuum_, according to the same _Aristotle_ himself, there is none, and were there, nothing would move in it: there remains the Region of Fire, but being so far distant from us, what Experiment can a.s.sure us, or hath a.s.sertained _Aristotle_ in such sort, that he should as of a thing most obvious to sence, affirm what he produceth in confutation of _Democritus_, to wit, that a great Ma.s.s of Air, is moved no swifter than a little one of water? But I will dwell no longer upon this matter, whereon I have spoke sufficiently: but leaving _Democritus_, I return to the Text of _Aristotle_, wherein he goes about to render the true reason, how it comes to pa.s.s, that the thin Plates of Iron or Lead do swim on the water; and, moreover, that Gold it self being beaten into thin Leaves, not only swims in water, but flyeth too and again in the Air. He supposeth that of Continualls[91], some are easily divisible, others not: and that of the easily divisible, some are more so, and some less: and these he affirms we should esteem the Causes.

He addes that that is easily divisible, which is well terminated, and the more the more divisible, and that the Air is more so, than the water, and the water than the Earth. And, lastly, supposeth that in each kind, the lesse quant.i.ty is easlyer divided and broken than the greater.

[91] _De Caelo_ l. 4. c. 6. t. 44.

Here I note, that the Conclusions of _Aristotle_ in generall are all true, but methinks, that he applyeth them to particulars, in which they have no place, as indeed they have in others, as for Example, Wax is more easily divisible than Lead, and Lead than Silver, inasmuch as Wax receives all the terms more easlier than Lead, and Lead than Silver. Its true, moreover, that a little quant.i.ty of Silver is easlier divided than a great Ma.s.s: and all these Propositions are true, because true it is, that in Silver, Lead and Wax, there is simply a Resistance against Division, and where there is the absolute, there is also the respective. But if as well in water as in Air, there be no Renitence against simple Division, how can we say, that the water is easlier divided than the Air? We know not how to extricate our selves from the Equivocation: whereupon I return to answer, that Resistance of absolute Division is one thing, and Resistance of Division made with such and such Velocity is another. But to produce Rest, and to abate the Motion, the Resistance of absolute Division is necessary; and the Resistance of speedy Division, causeth not Rest, but slowness of Motion. But that as well in the Air, as in water, there is no Resistance of simple Division, is manifest, for that there is not found any Solid Body which divides not the Air, and also the water: and that beaten Gold, or small dust, are not able to superate the Resistance of the Air, is contrary to that which Experience shews us, for we see Gold and Dust to go waving to and again in the Air, and at last to descend downwards, and to do the same in the water, if it be put therein, and separated from the Air. And, because, as I say, neither the water, nor the Air do resist simple Division, it cannot be said, that the water resists more than the Air. Nor let any object unto me, the Example of most light Bodies, as a Feather, or a little of the pith of Elder, or water-reed that divides the Air and not the water, and from this infer, that the Air is easlier divisible than the water; for I say unto them, that if they do well observe, they shall see the same Body likewise divide the Continuity of the water[92], and submerge in part, and in such a part, as that so much water in Ma.s.s would weigh as much as the whole Solid. And if they shal yet persist in their doubt, that such a Solid sinks not through inability to divide the water, I will return them this reply, that if they put it under water, and then let it go, they shall see it divide the water, and presently ascend with no less celerity, than that with which it divided the Air in descending: so that to say that this Solid ascends in the Air, but that coming to the water, it ceaseth its Motion, and therefore the water is more difficult to be divided, concludes nothing: for I, on the contrary, will propose them a piece of Wood, or of Wax, which riseth from the bottom of the water, and easily divides its Resistance, which afterwards being arrived at the Air, stayeth there, and hardly toucheth it; whence I may aswell say, that the water is more easier divided than the Air.

[92] _Archimed. De Insident. humi_ lib. 2. prop. 1.