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, asserting that a
Mass 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 spacious Figure, hath a great quantity
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 quantity 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 quantity 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 quantity 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 quantity 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
Assertion 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
pass, 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 assertion
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 asserted
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 Crassitude: 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 quantity, 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 accumulated 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 Balls 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 Crassitudes 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 passeth 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 quantity 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 Crassitude, 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 principal 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 Crassitude 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 Multitude
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, constituted in its naturall
Coldness. But if we take a Vessel of Glass, or Brass, 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 Mass of water, which shall
have more of Fire, than a small Mass of Air, and a great Mass of Air,
which shall have more of Earth than a little Mass of water, whereby it
would ensue, that a great Mass of Air, should come more swiftly
downwards, than a little quantity 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 Mass of Air taken, which
contains more Earth, than a small quantity of water, but yet will
deny, that such a Mass of Air, shall go faster downwards than a little
water, and that for many reasons. First, because if the greater
quantity of Earth, contained in the great Mass of Air, ought to cause
a greater Velocity than a less quantity of Earth, contained in a
little quantity of water, it would be necessary, first, that it were
true, that a greater Mass 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 Mass of Air, by
reason of the much Earth contained in it, do descend more swiftly than
a little Mass of water[90], but on the contrary, any whatsoever Mass of
water, shall move more swiftly than any other of Air, by reason the
participation 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 Mass 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
quantity of water, it might with more probability have been pretended,
that the great quantity of Air, ought to descend with a greater
_Impetus_, than the little quantity of water.
[89] The greater Specificall, not the greater absolute Gravity,
is the Cause of Velocity.
[90] Any Mass 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 participate 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 Mass of Air, whose Gravity shall exceed the Gravity of a little
quantity of water, and therefore such a Mass 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 participate 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 Mass of Air should move more
swiftly than a small Mass 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 participation others
assign 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 assure us, or hath
assertained _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 Mass 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 pass, 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 quantity 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 quantity of Silver is
easlier divided than a great Mass: 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 Mass
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.
I will not on this occasion forbear to give warning of another fallacy
of these persons, who attribute the reason of sinking or swimming to
the greater or lesse Resistance of the Crassitude of the water against
Division, making use of the example of an Egg, which in sweet water
goeth to the bottom, but in salt water swims; and alledging for the
cause thereof, the faint Resistance of fresh water against Division,
and the strong Resistance of salt water. But if I mistake not, from
the same Experiment, we may aswell deduce the quite contrary; namely,
that the fresh water is more dense, and the salt more tenuous and
subtle, since an Egg from the bottom of salt water speedily ascends to
the top, and divides its Resistance, which it cannot do in the fresh,
in whose bottom it stays, being unable to rise upwards. Into such like
perplexities, do false Principles Lead men: but he that rightly
Philosophating, shall acknowledge the excesses of the Gravities of the
Moveables and of the Mediums, to be the Causes of those effects, will
say, that the Egg sinks to the bottom in fresh water, for that it is
more grave than it, and swimeth in the salt, for that its less grave
than it: and shall without any absurdity, very solidly establish his
Conclusions.
Therefore the reason totally ceaseth, that _Aristotle_ subjoyns in the
Text saying[93]; The things, therefore, which have great breadth remain
above, because they comprehend much, and that which is greater, is not
easily divided. Such discoursing ceaseth, I say, because its not true,
that there is in water or in Air any Resistance of Division; besides
that the Plate of Lead when it stays, hath already divided and
penetrated the Crassitude of the water, and profounded it self ten or
twelve times more than its own thickness: besides that such Resistance
of Division, were it supposed to be in the water, could not rationally
be affirmed to be more in its superiour parts than in the middle, and
lower: but if there were any difference, the inferiour should be the
more dense, so that the Plate would be no less unable to penetrate the
lower, than the superiour parts of the water; nevertheless we see that
no sooner do we wet the superiour Superficies of the Board or thin
Piece of Wood, but it precipitatly, and without any retension,
descends to the bottom.
[93] Text 45.
I believe not after all this, that any (thinking perhaps thereby to
defend _Aristotle_) will say, that it being true, that the much water
resists more than the little, the said Board being put lower
descendeth, because there remaineth a less Mass of water to be divided
by it: because if after the having seen the same Board swim in four
Inches of water, and also after that in the same to sink, he shall try
the same Experiment upon a profundity of ten or twenty fathom water,
he shall see the very self same effect. And here I will take occasion
to remember, for the removall of an Error that is too common; That
that Ship or other whatsoever Body, that on the depth of an hundred or
a thousand fathom, swims with submerging only six fathom of its own
height, [_or in the Sea dialect, that draws six fathom water_] shall
swim in the same manner in water, that hath but six fathom and half an
Inch of depth[94]. Nor do I on the other side, think that it can be said,
that the superiour parts of the water are the more dense, although a
most grave Authour hath esteemed the superiour water in the Sea to be
so, grounding his opinion upon its being more salt, than that at the
bottom: but I doubt the Experiment, whether hitherto in taking the
water from the bottom, the Observatour did not light upon some spring
of fresh water there spouting up: but we plainly see on the contrary,
the fresh Waters of Rivers to dilate themselves for some miles beyond
their place of meeting with the salt water of the Sea, without
descending in it, or mixing with it, unless by the intervention of
some commotion or turbulency of the Windes.
[94] A Ship that in 100 Fathome water draweth 6 Fathome, shall
float in 6 Fathome and 1/2 an Inch of depth.
But returning to _Aristotle_, I say, that the breadth of Figure hath
nothing to do in this business more or less, because the said Plate of
Lead, or other Matter, cut into long Slices, swim neither more nor
less[95]; and the same shall the Slices do, being cut anew into little
pieces, because its not the breadth but the thickness that operates in
this business. I say farther, that in case it were really true, that
the Renitence to Division were the proper Cause of swimming[96], the
Figures more narrow and short, would much better swim than the more
spacious and broad, so that augmenting the breadth of the Figure, the
facility of supernatation will be deminished, and decreasing, that
this will encrease.
[95] Thickness not breadth of Figure to be respected in Natation.
[96] Were Renitence the cause of Natation, breadth of Figure would
hinder the swiming of Bodies.
And for declaration of what I say, consider that when a thin Plate of
Lead descends, dividing the water, the Division and discontinuation is
made between the parts of the water, invironing the perimeter or
Circumference of the said Plate, and according to the bigness greater
or lesser of that circuit, it hath to divide a greater or lesser
quantity of water, so that if the circuit, suppose of a Board, be ten
Feet in sinking it flatways, it is to make the seperation and
division, and to so speak, an incission upon ten Feet of water; and
likewise a lesser Board that is four Feet in Perimeter, must make an
incession of four Feet. This granted, he that hath any knowledge in
Geometry, will comprehend, not only that a Board sawed in many long
thin pieces, will much better float than when it was entire, but that
all Figures, the more short and narrow they be, shall so much the
better swim. Let the Board A B C D be, for Example, eight Palmes long,
and five broad, its circuit shall be twenty six Palmes; and so many
must the incession be, which it shall make in the water to descend
therein: but if we do saw ir, as suppose into eight little pieces,
according to the Lines E F, G H, {&}c. making seven Segments, we must
adde to the twenty six Palmes of the circuit of the whole Board,
seventy others; whereupon the eight little pieces so cut and
seperated, have to cut ninty six Palmes of water. And, if moreover, we
cut each of the said pieces into five parts, reducing them into
Squares, to the circuit of ninty six Palmes, with four cuts of eight
Palmes apiece; we shall adde also sixty four Palmes, whereupon the
said Squares to descend in the water, must divide one hundred and
sixty Palmes of water, but the Resistance is much greater than that of
twenty six; therefore to the lesser Superficies, we shall reduce them,
so much the more easily will they float: and the same will happen in
all other Figures, whose Superficies are simular amongst themselves,
but different in bigness: because the said Superficies, being either
deminished or encreased, always diminish or encrease their Perimeters
in subduple proportion; to wit, the Resistance that they find in
penetrating the water; therefore the little pieces gradually swim,
with more and more facility as their breadth is lessened.
[Illustration]
_This is manifest; for keeping still the same height of the Solid,
with the same proportion as the Base encreaseth or deminisheth,
doth the said Solid also encrease or diminish; whereupon the Solid
more diminishing than the Circuit, the Cause of Submersion more
diminisheth than the Cause of Natation: And on the contrary, the
Solid more encreasing than the Circuit, the Cause of Submersion
encreaseth more, that of Natation less._
And this may all be deduced out of the Doctrine of _Aristotle_ against
his own Doctrine.
Lastly, to that which we read in the latter part of the Text[97], that is
to say, that we must compare the Gravity of the Moveable with the
Resistance of the Medium against Division, because if the force of the
Gravity exceed the Resistance of the _Medium_, the Moveable will
descend, if not it will float. I need not make any other answer, but
that which hath been already delivered; namely, that its not the
Resistance of absolute Division, (which neither is in Water nor Air)
but the Gravity of the _Medium_ that must be compared with the Gravity
of the Moveables; and if that of the _Medium_ be greater, the Moveable
shall not descend, nor so much as make a totall Submersion, but a
partiall only; because in the place which it would occupy in the
water, there must not remain a Body that weighs less than a like
quantity of water: but if the Moveable be more grave, it shall descend
to the bottom, and possess a place where it is more conformable for it
to remain, than another Body that is less grave. And this is the only
true proper and absolute Cause of Natation and Submersion, so that
nothing else hath part therein: and the Board of the Adversaries
swimmeth, when it is conjoyned with as much Air, as, together with it,
doth form a Body less grave than so much water as would fill the place
that the said Compound occupyes in the water; but when they shall
demit the simple Ebony into the water, according to the Tenour of our
Question, it shall alwayes go to the bottom, though it were as thin as
a Paper.
[97] Lib. 4. c. 6. Text 45.
[Decoration]