That I might be satisfi’d, whether it were not possible to make an
_Artificial_ pore as _small_ as any _Natural_ I had yet found, I made
several attempts with small _glass pipes_, melted in the flame of a Lamp,
and then very _suddenly_ drawn out into a great length. And, by _that
means_, without much difficulty, I was able to draw some almost as small as
a _Cobweb_, which yet, with the _Microscope_, I could plainly perceive[7]
to be _perforated_, both by looking on the _ends_ of it, and by looking on
it _against the light_ which was much the _easier way_ to determine whether
it were solid or perforated; for, taking a small pipe of glass, and closing
one end of it, then filling it _half full_ of water, and holding it
_against the light_, I could, by this means, very easily find what was the
_differing aspect_ of a _solid_ and a _perforated_ piece of glass; and so
easily distinguish, without seeing either end, whether any _Cylinder_ of
glass I look’d on, were a _solid stick_, or a _hollow cane_. And by this
means, I could also presently judge of any small _filament_ of glass,
whether it were _hollow_ or _not_, which would have been exceeding tedious
to examine by looking on the end. And many such like ways I was fain to
make use of, in the examining of divers other particulars related in this
Book, which would have been no easie task to have determined meerly by the
more common way of looking on, or viewing the Object. For, if we consider
first, the very _faint light_ wherewith the object is enlightened, whence
many particles appear _opacous_, which when more enlightned, appear very
_transparent_, so that I was fain to _determine_ its _transparency_ by one
glass, and its _texture_ by another. Next, the _unmanageableness_ of most
_Objects_, by reason of their _smalness_, 3. The _difficulty of finding_
the desired point, and of _placing_ it so, as to reflect the _light
conveniently_ for the Inquiry. Lastly, ones being able to view it but with
_one eye_ at once, they will appear no small _obstructions_, nor are they
easily _remov’d_ without many _contrivances_. But to proceed, I could not
find that water, or some _deeply ting’d_ liquors would in small ones rise
so high as one would expect; and the _highest_ I have found it yet rise in
any of the pipes I have try’d, was to 21 _inches_ above the level of the
water in the vessel: for though I found that in the small pipes it would
_nimbly enter_ at first, and run about 6 or 7 _inches_ upwards; yet I found
it then to move upwards _so slow_, that I have not yet had the _patience_
to observe it above that height of 21 _inches_ (and that was in a pretty
_large Pipe_, in comparison of those I formerly mentioned; for I could
observe the _progress_ of a _very deep ting’d liquor_ in it with my _naked
eye_, without much trouble; whereas many of the _other pipes_ were so _very
small_, that unless in a _convenient posture_ to the light, I could not
perceive _them_:) But ’tis very probable, that a greater _patience_ and
_assiduity_ may discover the liquors to _rise_, at least to remain
_suspended_, at heights that I should be loath now even to _ghess_ at, if
at least there be any _proportion_ kept between the height of the ascending
liquor, and the _bigness of the holes_ of the pipes.
_AN ATTEMPT FOR THE EXPLICATION OF THIS EXPERIMENT._
My Conjecture, _That the unequal height of the surfaces of the water,
proceeded from the greater pressure made upon the water by the Air without
the Pipes_ ABC, _then by that within them_[8]; I shall endeavour to confirm
from the truth of the two following _Propositions_:
The first of which is, _That an unequal pressure of the incumbent Air, will
cause an unequal height in the water’s Surfaces_.
And the second is, _That in this experiment there is such an unequal
pressure_.
That the first is true, the following _Experiment_ will evince. For if you
take any Vessel so contrived, as that you can at pleasure either _increase_
or _diminish_ the _pressure_ of the Air upon this or that part of the
_Superficies_ of the _water_, the _equality_ of the height of those parts
will presently be _lost_; and that part of the _Superficies_ that sustains
the _greater pressure_, will be _inferior_ to that which undergoes the
_less_. A fit Vessel for this purpose, will be an inverted Glass _Syphon_,
such an one as is described in the _Sixth Figure_. For if into it you put
Water enough to fill it as high as _AB_, and gently blow in at _D_, you
shall _depress_ the Superficies _B_, and thereby _raise_ the opposite
Superficies _A_ to a _considerable height_, and by gently _sucking_ you may
produce clean _contrary_ effects.
Next, That there is such an _unequal pressure_, I shall prove from this,
_That there is a much greater incongruity of Air to Glass, and some other
Bodies, then there is of Water to the same_.
By _Congruity, I mean a property of a fluid Body, whereby any part of it is
readily united with any other part, either of itself, or of any other
Similar, fluid, or solid body: And by Incongruity a property of a fluid, by
which it is hindred from uniting with any dissimilar, fluid, or solid
Body._
This last property, any one that hath been observingly conversant about
fluid Bodies, cannot be ignorant of. For (not now to mention several
_Chymical Spirits_ and _Oyls_, which will _very hardly_, if at _all_, be
brought to _mix_ with one another; insomuch that there may be found some 8
or 9, or more, several distinct Liquors, which _swimming_ one upon another,
will not presently _mix_) we need seek no further for Examples of this kind
in _fluids_, then to observe the _drops of rain_ falling through the _air_
and the _bubbles of air_ which are by any means conveyed under the surface
of the _water_; or a drop of common _Sallet-Oyl_ swimming upon water. In
all which, and many more examples of this kind that might be enumerated,
the _incongruity_ of two _fluids_ is easily discernable. And as for the
_Congruity_ or _Incongruity_ of Liquids, with several kinds of _firm_
Bodies, they have long since been taken notice of, and called by the Names
of _Driness_ and _Moisture_ (though these two names are not comprehensive
enough, being commonly used to signifie only the adhering or not adhering
of _water_ to some other _solid Bodies_) of this kind we may observe that
_water_ will more readily _wet some woods_ then _others_; and that _water_,
let fall upon a _Feather_, the whiter side of a _Colwort_, and some other
leaves, or upon almost any _dusty_, _unctuous_, or _resinous_ superficies,
will not _at all adhere_ to them, but easily _tumble off_ from them, like a
solid _Bowl_; whereas, if dropt upon _Linnen_, _Paper_, _Clay_, _green
Wood_, &c. it will not be taken off, without leaving some part of it behind
_adhering_ to them. So _Quick-silver_, which will very _hardly_ be brought
to _stick_ to any _vegetable body_, will _readily adhere_ to, and _mingle_
with, several clean _metalline bodies_.
And that we may the better finde what the _cause_ of _Congruity_ and
_Incongruity_ in bodies is, it will be requisite to consider, First, what
is the _cause_ of _fluidness_; And this, _I conceive_, to be nothing else
but a certain _pulse_ or _shake_ of _heat_; for Heat being nothing else but
a very _brisk_ and _vehement agitation_ of the parts of a body (as I have
elswhere made _probable_) the parts of a body are thereby made so _loose_
from one another, that they easily _move any way_, and become _fluid_. That
I may explain this a little by a gross Similitude, let us suppose a dish of
sand set upon some body that is very much _agitated_, and shaken with some
_quick_ and _strong vibrating motion_, as on a _Milstone_ turn’d round upon
the under stone very violently whilst it is empty; or on a very stiff
_Drum_-head, which is vehemently or very nimbly beaten with the Drumsticks.
By this means, the sand in the dish, which before lay like a _dull_ and
unactive body, becomes a perfect _fluid_; and ye can no sooner make a
_hole_ in it with your finger, but it is immediately _filled up again_, and
the upper surface of it _levell’d_. Nor can you _bury_ a _light body_, as a
piece of Cork under it, but it presently _emerges_ or _swims_ as ’twere on
the top; nor can you lay a _heavier_ on the top of it, as a piece of Lead,
but it is immediately _buried_ in Sand, and (as ’twere) sinks to the
bottom. Nor can you make a _hole_ in the side of the Dish, but the sand
shall _run out_ of it to a _level_, not an _obvious property_ of a fluid
body, as such, but this dos _imitate_; and all this meerly caused by the
vehement _agitation_ of the conteining vessel; for by this means, _each_
sand becomes to have a _vibrative_ or _dancing_ motion, so as no other
heavier body can _rest_ on it, unless _sustein’d_ by some other on either
side: Nor will it suffer any Body to be _beneath_ it, unless it be a
_heavier_ then it self. Another Instance of the strange _loosening_ nature
of a violent jarring Motion, or a strong and nimble vibrative one, we may
have from a piece of _iron_ grated on very strongly with a _file_: for if
into that a pin _screw’d_ so firm and hard, that though it has a convenient
head to it, yet it can by no means be _unscrew’d_ by the fingers; if, I
say, you attempt to unscrew this whilst _grated on by the file_, it will be
found to undoe and turn very _easily_. The first of these Examples
manifests, how a body actually _divided_ into small parts, becomes a
_fluid_. And the latter manifests by what means the agitation of heat so
easily _loosens_ and _unties_ the parts of _solid_ and _firm_ bodies. Nor
need we suppose heat to be any thing else, besides such a motion; for
supposing we could _Mechanically_ produce such a one _quick_ and _strong_
enough, we need not spend _fuel_ to _melt_ a body. Now, that I do not speak
this altogether groundless, I must refer the Reader to the Observations I
have made upon the shining sparks of Steel, for there he shall find that
_the same_ effects are produced upon small chips or parcels of Steel by the
_flame_, and by _a quick and violent motion_; and if the body of _steel_
may be thus melted (as I there shew it may) I think we have little reason
to doubt that almost _any other_ may not also. Every Smith can inform one
how quickly both his _File_ and the _Iron_ grows _hot_ with _filing_, and
if you _rub_ almost any two _hard_ bodies together, they will do the same:
And we know, that a sufficient degree of heat causes _fluidity_, in some
bodies much sooner, and in others later; that is, the parts of the body of
some are so _loose_ from one another, and so _unapt to cohere_, and so
_minute_ and _little_, that a very _small_ degree of agitation keeps them
always in the _state of fluidity_. Of this kind, I suppose, the _Æther_,
that is the _medium_ or _fluid_ body, in which all other bodies do as it
were swim and move; and particularly, the _Air_, which seems nothing else
but a kind of _tincture_ or _solution_ of terrestrial and aqueous particles
_dissolv’d_ into it, and agitated by it, just as the _tincture_ of
_Cocheneel_ is nothing but some finer _dissoluble_ parts of that Concrete
lick’d up or _dissolv’d_ by the _fluid_ water. And from this Notion of it,
we may easily give a more Intelligible reason how the Air becomes so
capable of _Rarefaction_ and _Condensation_. For, as in _tinctures_, one
grain of some _strongly tinging_ substance may _sensibly_ colour some
_hundred thousand_ grains of _appropriated_ Liquors, so as every _drop_ of
it has its proportionate share, and be sensibly ting’d, as I have try’d
both with _Logwood_ and _Cocheneel_: And as some few grains of _Salt_ is
able to infect as great a quantity, as may be found by _præcipitations_,
though not so easily by the _sight_ or _taste_; so the _Air_, which seems
to be but as ’twere a _tincture_ or _saline substance, dissolv’d and
agitated by the fluid and agil Æther_, may disperse and _expand_ it self
into a _vast space_, if it have room enough, and infect, as it were, every
part of that space. But, as on the other side, if there be but some _few
grains_ of the liquor, it may _extract all_ the colour of the tinging
substance, and may _dissolve_ all the Salt, and thereby become _much more
impregnated_ with those substances, so may _all_ the air that sufficed in a
_rarify’d state_ to fill some _hundred thousand_ spaces of Æther, be
compris’d in only _one_, but in a position proportionable _dense_. And
though we have not yet found out such _strainers_ for Tinctures and Salts
as we have for the Air, being yet unable to _separate_ them from their
dissolving liquors by any kind of _filtre_, without _præcipitation_, as we
are able to _separate_ the Air from the Æther by _Glass_, and several other
bodies. And though we are yet unable and ignorant of the ways of
_præcipitating_ Air out of the Æther as we can Tinctures, and Salts out of
several _dissolvents_; yet neither of these seeming _impossible_ from the
nature of the things, nor so _improbable_ but that some happy future
industry may find out ways to effect them; nay, further, since we find that
Nature _does really perform_ (though by what means we are not certain) both
these actions, namely, by _præcipitating_ the Air in Rain and Dews, and by
supplying the Streams and Rivers of the World with fresh water, _strain’d_
through secret subterraneous Caverns: And since, that in very many other
_proprieties_ they do so exactly _seem_ of the _same nature_; till further
observations or tryals do inform us of the _contrary_, we may _safely
enough conclude_ them of the _same kind_. For it seldom happens that any
two natures have so many properties _coincident_ or the _same_, as I have
observ’d Solutions and Air to have, and to be _different_ in the rest. And
therefore I think it neither _impossible_, _irrational_, nay nor
_difficult_ to be able to _predict_ what is _likely_ to happen in other
particulars also, besides those which _Observation_ or _Experiment_ have
declared thus or thus; especially, if the _circumstances_ that do often
very much conduce to the variation of the effects be duly _weigh’d_ and
_consider’d_. And indeed, were there not a _probability_ of this, our
_inquiries_ would be _endless_, our _tryals vain_, and our greatest
_inventions_ would be nothing but the meer _products_ of _chance_, and not
of _Reason_; and, like _Mariners_ in an Ocean, destitute both of a
_Compass_ and the sight of the _Celestial guides_, we might indeed, _by
chance_, Steer _directly_ towards our desired Port, but ’tis _a thousand to
one_ but we _miss_ our aim. But to proceed, we may hence also give a plain
reason, how the Air comes to be _darkned_ by _clouds_, &c. which are
nothing but a kind of _precipitation_, and how those _precipitations_ fall
down in _Showrs_. Hence also could I very easily, and I think truly, deduce
the cause of the curious _sixangular figures_ of Snow, and the appearances
of _Haloes, &c._ and the sudden _thickning_ of the Sky with Clouds, and the
_vanishing_ and _disappearing_ of those Clouds again; for all these things
may be very easily _imitated_ in a _glass of liquor_, with some slight
_Chymical preparations_ as I have often try’d, and may somewhere else more
largely relate, but have not now time to set them down. But to proceed,
there are other bodies that consist of particles more _Gross_, and of a
more _apt_ figure for _cohesion_, and this requires _somewhat greater_
agitation; such, I suppose ☿, _fermented vinous_ _Spirits_, several
_Chymical Oils_, which are much of kin to those Spirits, &c. Others yet
require a _greater_, as _water_, and so others _much greater_, for almost
infinite degrees: For, I suppose there are very _few_ bodies in the world
that may not be made _aliquatenus_ fluid, by _some_ or _other_ degree of
agitation or heat.
Having therefore in short set down my Notion of a Fluid body, I come in the
next place to consider what _Congruity_ is; and this, as I said before,
being a _Relative property_ of a fluid, whereby it may be said to be _like_
or _unlike_ to this or that other body, whereby it _does_ or _does not mix_
with this or that body. We will again have recourse to our former
Experiment, though but a rude one; and here if we mix in the dish _several
kinds_ of sands, some of _bigger_, others of _less_ and finer bulks, we
shall find that by the agitation _the fine sand_ will _eject_ and _throw
out_ of it self all those _bigger_ bulks of small _stones_ and the like,
and those will _be gathered_ together all into _one_ place; and if there be
_other_ bodies in it of other natures, those also will be _separated_ into
a place by themselves, and _united_ or _tumbled_ up together. And though
this do not come up to the _highest property_ of _Congruity_, which is a
_Cohæsion_ of the parts of the fluid together, or a kind of _attraction_
and _tenacity_, yet this does as ’twere _shadow_ it out, and somewhat
resemble it; for just after the same manner, I suppose the _pulse_ of heat
to _agitate_ the small parcels of matter, and those that are of a _like
bigness_, and _figure_, and _matter_, will _hold_, or _dance_ together, and
those which are of a _differing_ kind will be _thrust_ or _shov’d_ out from
between them; for particles that are _similar_, will, like so many _equal
musical strings equally stretcht_, vibrate together in a kind of _Harmony_
or _unison_; whereas others that are _dissimilar_, upon what account
soever, unless the disproportion be otherwise counter-ballanc’d, will, like
so many _strings out of tune_ to those unisons, though they have the same
agitating _pulse_, yet make quite _differing_ kinds of _vibrations_ and
_repercussions_, so that though they may be both mov’d, yet are their
_vibrations_ so _different_, and so _untun’d_, as ’twere to each other,
that they _cross_ and _jar_ against each other, and consequently, _cannot
agree_ together, but _fly back_ from each other to their similar particles.
Now, to give you an instance how the _disproportion_ of some bodies in one
respect, may be _counter-ballanc’d_ by a _contrary disproportion_ of the
same body in another respect, whence we find that the subtil _vinous
spirit_ is _congruous_, or does readily _mix_ with _water_, which in many
properties is of a very _differing nature_, we may consider that a _unison_
may be made either by two _strings_ of the same _bigness_, _length_, and
_tension_, or by two strings of the same _bigness_, but of _differing
length_, and a _contrary differing tension_, or _3ly._ by two strings of
_unequal length_ and _bigness_, and of a _differing tension_, or of _equal
length_, and _differing bigness_ and _tension_, and several other such
varieties. To which _three properties_ in _strings_, will correspond _three
proprieties_ also in _sand_, or the _particles_ of bodies, their _Matter_
or _Substance_, their _Figure_ or _Shape_, and their _Body_ or _Bulk_. And
from the _varieties_ of these _three_, may arise _infinite varieties_ in
fluid bodies, though all agitated by the _same pulse_ or _vibrative_
motion. And there may be as many ways of making Harmonies and Discords with
these, as there may be with _musical strings_. Having therefore seen what
is the cause of Congruity or Incongruity, those relative properties of
fluids, we may, from what has been said, very easily collect, what is the
_reason_ of those Relative proprieties also between _fluid bodies_ and
_solid_; for since all bodies consist of _particles_ of such a _Substance_,
_Figure_, and _Bulk_; but in some they are _united_ together more _firmly_
then to be _loosened_ from each other by every _vibrative_ motion (though I
imagine that there is no body in the world, but that some degree of
agitation may, as I hinted before, agitate and loosen the particles so as
to make them fluid) those _cohering_ particles may _vibrate_ in the same
manner almost as those that are _loose_ and become _unisons_ or _discords_,
as I may so speak, to them. Now that the _parts_ of all _bodies_, though
never so _solid_, do yet _vibrate_, I think we need go no further for
proof, then that _all_ bodies have some _degrees_ of _heat_ in them, and
that there has not been yet found any thing _perfectly cold_: Nor can I
believe indeed that there is any such thing in Nature, as a body whose
particles are at _rest_, or _lazy_ and _unactive_ in the great _Theatre_ of
the _World_, it being quite _contrary_ to the grand _Oeconomy_ of the
Universe. We see therefore what is the reason of the _sympathy_ or uniting
of some bodies together, and of the _antipathy_ or flight of others from
each other: For _Congruity_ seems nothing else but a _Sympathy_, and
_Incongruity_ an _Antipathy_ of bodies, hence _similar_ bodies once
_united_ will not _easily part_, and _dissimilar_ bodies once _disjoyn’d_
will not _easily unite_ again; from hence may be very easily deduc’d the
reason of the _suspension_ of _water_ and _Quick-silver_ above their usual
_station_, as I shall more at large anon shew.
These properties therefore (alwayes the concomitants of fluid bodies)
produce these following visible _Effects_:
First, They _unite_ the parts of a fluid to its _similar_ Solid, or keep
them _separate_ from its _dissimilar_. Hence _Quick-silver_ will (as we
noted before) _stick_ to _Gold_, _Silver_, _Tin_, _Lead_, &c. and _unite_
with them: but _roul_ off from _Wood_, _Stone_, _Glass_, &c. if never so
little scituated out of its _horizontal level_; and _water_ that will _wet
salt_ and _dissolve_ it, will _slip_ off from _Tallow_, or the like,
without at all _adhering_; as it may likewise be observed to do upon a
_dusty_ superficies. And next they cause the parts of _homogeneal fluid_
bodies readily to _adhere_ together and _mix_, and of _heterogeneal_, to be
exceeding _averse_ thereunto. Hence we find, that _two_ small _drops_ of
_water_, on any superficies they can roul on, will, if they chance to touch
each other, _readily unite_ and _mix_ into one 3d _drop_: The like may be
observed with two small _Bowls_ of _Quick-silver_ upon a Table or Glass,
provided their surfaces be not _dusty_; and with two drops of _Oyl_ upon
fair water, _&c._ And further, _water_ put unto _wine_, _salt water_,
_vinegar_, _spirit_ of _wine_, or the like, does immediately (especially if
they be shaken together) _disperse_ it self all over them. Hence, on the
contrary, we also find, that _Oyl of Tartar_ poured upon _Quick-silver_,
and _Spirit of Wine_ on that _Oyl_, and _Oyl of Turpentine_ on that
_Spirit_, and _Air_ upon that _Oyl_, though they be stopt closely up into a
Bottle, and _shaken_ never so much, they will by no means long suffer any
of their bigger parts to be _united_ or included within any of the other
Liquors (by which recited Liquors, may be plainly enough represented the
four _Peripatetical Elements_, and the more subtil _Æther_ above all.) From
this property ’tis, that a drop of _water_ does not mingle with, or vanish
into _Air_, but is _driven_ (by that Fluid equally protruding it on every
side) and forc’t into as little a space as it can possibly be contained in,
namely, into a _Round Globule_. So likewise a little _Air_ blown under the
_water_, is _united_ or thrust into a _Bubble_ by the ambient water. And a
parcel of _Quick-silver_ enclosed with _Air_, _Water_, or almost any other
_Liquor_, is _formed_ into a _round Ball_.
Now the cause why all these included Fluids, newly mentioned, or as many
others as are wholly included within a heterogeneous fluid, are not
_exactly_ of a _Spherical Figure_ (seeing that if caused by these
Principles only, it could be of no other) must proceed from some other kind
of _pressure_ against the two opposite flatted sides. This _adventitious_
or _accidental pressure_ may proceed from _divers causes_, and accordingly
must _diversifie_ the Figure of the included heterogeneous fluid: For
seeing that a body may be included either with a fluid only, or only with a
solid, or partly with a fluid, and partly with a solid, or partly with one
fluid, and partly with another; there will be found a very great variety of
the terminating _surfaces_, much differing from a _Spherical_, according to
the various resistance or pressure that belongs to each of these
encompassing bodies.
Which Properties may in general be deduced from two heads, _viz._ _Motion_,
and _Rest_. For, either this Globular Figure is altered by a _natural
Motion_, such as is _Gravity_, or a _violent_, such as is any _accidental
motion_ of the fluids, as we see in the _wind_ ruffling up the water, and
the _purlings_ of _Streams_, and _foaming_ of _Catarracts_, and the like.
Or thirdly, By the _Rest_, _Firmness_ and _Stability_ of the ambient
_Solid_. For if the including _Solid_ be of an _angular_ or any other
_irregular_ Form, the included _fluid_ will be near of the _like_, as a
Pint-_Pot_ full of _water_, or a _Bladder_ full of _Air_. And next, if the
including or included fluid have a greater _gravity_ one than another, then
will the _globular_ Form be deprest into an _Elliptico-spherical_: As if,
for example, we suppose the Circle _ABCD_, in the _fourth Figure_, to
represent a _drop of water_, _Quick-silver_, or the like, included with the
_Air_ or the like, which supposing there were no _gravity_ at all in either
of the _fluids_, or that the _contained_ and _containing_ were of the _same
weight_, would be _equally comprest_ into an exactly _spherical_ body (the
ambient fluid _forcing equally_ against every side of it.) But supposing
either a greater _gravity_ in the included, by reason whereof the parts of
it being _prest_ from _A_ towards _B_, and thereby the whole put into
_motion_, and that _motion_ being _hindred_ by the _resistance_ of the
_subjacent_ parts of the ambient, the _globular_ Figure _ADBC_ will be
_deprest_ into the _Elliptico-spherical_, _EGFH_. For the side _A_ is
_detruded_ to _E_ by the _Gravity_, and _B_ to _F_ by the _resistance_ of
the subjacent medium: and therefore _C_ must necessarily be thrust to _G_;
and _D_ to _H_. Or else, supposing a greater _gravity_ in the _ambient_, by
whose more then ordinary _pressure_ against the under side of the included
globule; _B_ will be forced to _F_, and by its _resistance_ of the motion
_upwards_, the side _A_ will be _deprest_ to _E_, and therefore _C_ being
thrust to _G_ and _D_ to _H_; the _globular_ Figure by this means also will
be made an _Elliptico-spherical_. Next if a fluid be included _partly_ with
one, and _partly_ with another fluid, it will be found to be shaped
_diversly_, according to the proportion of the _gravity_ and _incongruity_
of the 3 _fluids_ one to another: As in the _second Figure_, let the upper
_MMM_ be _Air_, the middle _LMNO_ be common _Oyl_, the lower _OOO_ be
_Water_, the _Oyl_ will be form’d, not into a _spherical_ Figure, such as
is represented by the _pricked Line_, but into such a Figure as LMNO, whose
side LMN will be of a flatter _Elliptical_ Figure, by reason of the great
disproportion between the _Gravity_ of _Oyl_ and _Air_, and the side LOM of
a rounder, because of the smaller difference between the weight of _Oyl_
and _Water_. Lastly, The _globular_ Figure will be changed, if the
_ambient_ be partly _fluid_ and partly _solid_. And here the termination of
the incompassed _fluid_ towards the incompassing is shap’d according to the
proportion of the congruity or incongruity of the _fluids_ to the _solids_,
and of the gravity and incongruity of the _fluids_ one to another. As
suppose the subjacent _medium_ that hinders an included fluids descent, be
a _solid_, as let KI, in the _fourth Figure_, represent the smooth
superficies of a _Table_; EGFH, a parcel of _running Mercury_; the side GFH
will be more flatted, according to the proportion of the incongruity of the
_Mercury_ and _Air_ to the _Wood_, and of the _gravity_ of _Mercury_ and
_Air_ one to another; The side GEH will likewise be a little more deprest
by reason the subjacent parts are now at rest, which were before in motion.
Or further in the _third figure_, let AILD represent an including _solid_
medium of a cylindrical shape (as suppose a small _Glass Jar_) Let FGEMM
represent a contain’d _fluid_, as water; this towards the bottom and sides,
is figured according to the concavity of the _Glass_: But its upper
_Surface_, (which by reason of its gravity, (not considering at all the Air
above it, and so neither the congruity or incongruity of either of them to
the Glass) should be terminated by part of a _Sphere_ whose diameter should
be the same with that of the earth, which to our sense would appear a
straight _Line_, as FGE, Or which by reason of its having a greater
congruity to Glass than Air has, (not considering its Gravity) would be
thrust into a _concave Sphere_, as CHB, whose diameter would be the same
with that of the concavity of the Vessel:) Its upper Surface, I say, by
reason of its having a greater gravity then the Air, and having likewise a
greater congruity to Glass then the Air has, is terminated, by a _concave
Elliptico-spherical Figure_, as CKB. For by its congruity it easily
conforms it self, and adheres to the Glass, and constitutes as it were one
containing body with it, and therefore should thrust the contained Air on
that side it touches it, into a _spherical_ Figure, as BHC, but the motion
of Gravity depressing a little the Corners B and C, reduces it into the
aforesaid Figure CKB. Now that it is the greater congruity of one of the
two _contiguous fluids_, then of the other, to the containing _solid_, that
causes the separating surfaces to be thus or thus figured: And that it is
not because this or that figurated surface is more proper, natural, or
peculiar to one of these fluid bodies, then to the other, will appear from
this; that the same _fluids_ will by being put into differing _solids_,
change their _surfaces_. For the same water, which in a Glass or wooden
Vessel will have a concave surface upwards, and will rise higher in a
smaller then a greater Pipe, the same water, I say, in the same Pipes
greased over or oyled, will produce quite contrary effects; for it will
have a _protuberant_ and _convex_ surface upwards, and will not rise so
high in small, as in bigger Pipes: Nay, in the very same solid Vessel, you
may make the very same two contiguous _Liquids_ to alter their Surfaces;
for taking a small Wine-glass, or such like Vessel, and pouring water
gently into it, you shall perceive the _surface_ of the water all the way
_concave_, till it rise even with the top, when you shall find it (if you
gently and carefully pour in more) to grow very _protuberant_ and _convex_;
the reason of which is plain, for that the _solid_ sides of the containing
body are no longer extended, to which the water does more readily adhere
then the air; but it is henceforth to be included with air, which would
reduce it into a _hemisphere_, but by reason of its _gravity_, it is
flatted into an _Oval_. _Quicksilver_ also which to _Glass_ is more
incongruous then _Air_ (and thereby being put into a _Glass-pipe_, will not
adhere to it, but by the more _congruous air_ will be forced to have a very
_protuberant_ surface, and to rise higher in a greater then a lesser Pipe)
this _Quicksilver_ to clean _Metal_, especially to _Gold_, _Silver_, _Tin_,
_Lead_, &c. _Iron_ excepted, is more _congruous_ then _Air_, and will not
only stick to it, but have a _concave_ Surface like _water_, and rise
higher in a less, then in a greater Pipe.
In all these Examples it is evident, that there is an _extraordinary_ and
_adventitious force_, by which the _globular_ Figure of the contained
_heterogeneous_ fluid is altered; neither can it be imagined, how it should
otherwise be of any other Figure then _Globular_: For being by the
_heterogeneous_ fluid equally _protruded_ every way, whatsoever part is
_protuberant_, will be thereby _deprest_. From this cause it is, that in
its effects it does very much resemble a _round Spring_ (such as a _Hoop_.)
For as in a _round Spring_ there is required an additional _pressure_
against two opposite sides, to reduce it into an _Oval_ Form, or to force
it in between the sides of a _Hole_, whose _Diameter_ is less then that of
the _Spring_, there must be a considerable force or _protrusion_ against
_the concave_ or inner side of the _Spring_; So to alter this _spherical_
constitution of an included fluid body, there is required more pressure
against opposite sides to reduce it into an _Oval_; and, to press it into
an _Hole_ less in _Diameter_ then it self, it requires a greater
_protrusion_ against all the other sides, What degrees of force are
requisite to reduce them into longer and longer _Ovals_, or to press them
into less and less _holes_, I have not yet experimentally calculated; but
thus much by experiment I find in general, that there is alwayes required a
greater pressure to close them into longer _Ovals_, or protrude them into
smaller _holes_. The necessity and reason of this, were it requisite, I
could easily explain: but being not so necessary, and requiring more room
and time then I have for it at present, I shall here omit it; and proceed
to shew, that this may be presently found true, if Experiment be made with
a _round Spring_ (the way of making which trials is _obvious_ enough.) And
with the fluid bodies of _Mercury_, _Air_, _&c._ the way of trying which,
will be somewhat more difficult; and therefore I shall in brief describe
it. He therefore that would try with _Air_, must first be provided of a
_Glass-pipe_, made of the shape of that in the _fifth Figure_, whereof the
side AB, represents a straight _Tube_ of about three foot long, C,
represents another part of it, which consists of a _round Bubble_; so
ordered, that there is left a _passage_ or _hole_ at the top, into which
may be fastened with _cement_ several _small Pipes_ of determinate
_cylindrical_ cavities: as let the _hollow_ of
F. ¼
G. ⅙
H. ⅛
I. be ¹⁄₁₂ of an inch.
K. ¹⁄₁₆
L. ¹⁄₂₄
M. ¹⁄₃₂
&c.——
There may be added as many more, as the Experimenter shall think fit, with
holes continually decreasing by known quantities, so far as his senses are
able to help him; I say, so far, because there may be made _Pipes_ so small
that it will be impossible to perceive the _perforation_ with ones naked
eye, though by the help of a _Microscope_, it may easily enough be
perceived: Nay, I have made a _Pipe_ perforated from end to end, so small,
that with my naked eye I could very hardly see the body of it, insomuch
that I have been able to knit it up into a knot without breaking: And more
accurately examining one with my _Microscope_, I found it not so big as a
sixteenth part of one of the smaller hairs of my head which was of the
smaller and finer sort of hair, so that sixteen of these _Pipes_ bound
faggot-wise together, would but have equalized one single hair; how small
therefore must its _perforation_ be? It appearing to me through the
_Microscope_ to be a proportionably _thick-sided Pipe_.
To proceed then, for the trial of the Experiment, the Experimenter must
place the _Tube_ AB, perpendicular, and fill the _Pipe_ F (cemented into
the hole E) with water, but leave the _bubble_ C full of _Air_, and then
gently pouring in water into the Pipe AB, he must observe diligently how
high the water will rise in it before it protrude the _bubble_ of Air C,
through the narrow passage of F, and denote exactly the height of the
_Cylinder_ of water, then cementing in a second Pipe as G, and filling it
with water; he may proceed as with the former, denoting likewise the height
of the _Cylinder_ of water, able to protrude the _bubble_ C through the
passage of G, the like may he do with the next _Pipe_, and the next, &c. as
far as he is able: then comparing the several heights of the _Cylinders_,
with the several _holes_ through which each _Cylinder_ did force the _air_
(having due regard to the _Cylinders_ of water in the small _Tubes_) it
will be very easie to determine, what force is requisite to press the _Air_
into such and such _a hole_, or (to apply it to our present experiment) how
much of the pressure of the _Air_ is taken off by its ingress into smaller
and smaller _holes_. From the application of which to the entring of the
_Air_ into the bigger _hole_ of the _Vessel_, and into the smaller _hole_
of the _Pipe_, we shall clearly find, that there is a greater pressure of
the air upon the water in the _Vessel_ or greater _pipe_, then there is
upon that in the lesser _pipe_: For since the pressure of the _air_ every
way is found to be equal, that is, as much as is able to press up and
sustain a _Cylinder_ of _Quicksilver_ of two foot and a half high, or
thereabouts; And since of this pressure so many more degrees are required
to force the _Air_ into a smaller then into a greater _hole_ that is full
of a more congruous fluid. And lastly, since those degrees that are
requisite to press it in, are thereby taken off from the _Air_ within, and
the _Air_ within left with so many degrees of pressure less then the _Air_
without; it will follow, that the _Air_ in the less _Tube_ or _pipe_, will
have less pressure against the superficies of the _water_ therein, then the
_Air_ in the bigger: which was the minor Proposition to be proved.
The Conclusion therefore will necessarily follow, _viz._ That _this
unequal pressure of the Air caused by its ingress into unequal holes,
is a cause sufficient to produce this effect, without the help of any
other concurrent_; and therefore is probably the principal (if not the
only) cause of these _Phænomena_.
This therefore being thus explained, there will be divers _Phænomena_
explicable thereby, as, the rising of _Liquors_ in a _Filtre_, the rising
of _Spirit of Wine_, _Oyl_, _melted Tallow_, &c. in the _Week_ of a _Lamp_,
(though made of small _Wire_, _Threeds_ of _Asbestus_, _Strings_ of
_Glass_, or the like) the rising of _Liquors_ in a _Spunge_, piece of
_Bread_, _Sand_, &c. perhaps also the ascending of the _Sap_ in _Trees_ and
_Plants_, through their small, and some of them _imperceptible pores_, (of
which I have said more, on another occasion) at least the passing of it out
of the earth into their roots. And indeed upon the consideration of this
Principle, multitudes of other uses of it occurr’d to me, which I have not
yet so well examined and digested as to propound for _Axioms_, but only as
_Queries_ and _Conjectures_ which may serve as _hints_ toward some further
_discoveries_.
As first, Upon the consideration of the _congruity_ and _incongruity_ of
Bodies, as to _touch_, I found also the like _congruity_ and _incongruity_
(if I may so speak) as to the _Transmitting_ of the _Rates_ of Light: For
as in this regard, _water_ (not now to mention other Liquors) seems nearer
of affinity to _Glass_ then _Air_, and _Air_ then _Quicksilver_: whence an
_oblique Ray_ out of _Glass_, will pass into _water_ with very little
_refraction_ from the _perpendicular_, but none out of _Glass_ into _Air_,
excepting a _direct_, will pass without a very great refraction from the
perpendicular, nay any oblique Ray under thirty degrees, will not be
admitted into the Air at all. And _Quicksilver_ will neither admit oblique
or direct, but reflects all; seeming, as to the transmitting of the Raies
of Light, to be of a quite differing constitution, from that of _Air_,
_Water_, _Glass_, &c. and to resemble most those opacous and strong
reflecting bodies of Metals: So also as to the property of cohesion or
congruity, Water seems to keep the same order, being more congruous to
Glass then Air, and Air then Quicksilver.
A Second thing (which was hinted to me, by the consideration of the
included fluids globular form, caused by the protrusion of the ambient
heterogeneous fluid) was, whether the _Phænomena_ of gravity might not by
this means be explained, by supposing the _Globe_ of Earth, Water, and Air
to be included with a _fluid_, heterogeneous to all and each of them, so
subtil, as not only to be every where _interspersed_ through the _Air_, (or
rather the _air_ through it) but to _pervade_ the bodies of _Glass_, and
even the _closest Metals_, by which means it may endeavour to _detrude_ all
earthly bodies as far from it as it can; and partly thereby, and partly by
other of its properties may move them towards the Center of the Earth. Now
that there is some such fluid, I could produce many Experiments and
Reasons, that do seem to prove it: But because it would ask some time and
room to set them down and explain them, and to consider and answer all the
Objections (many whereof I foresee) that may be alledged against it; I
shall at present proceed to other _Queries_, contenting my self to have
here only given a hint of what I may say more elswhere.
A Third _Query_ then was, Whether the _heterogeneity_ of the _ambient
fluid_ may not be accounted a _secondary cause_ of the _roundness_ or
_globular form_ of the _greater bodies_ of the world, such as are those of
the _Sun_, _Stars_, and _Planets_, the _substance_ of each of which seems
altogether _heterogeneous_ to the _circumambient fluid æther_? And of this
I shall say more in the Observation of the Moon.
A Fourth was, Whether the _globular form_ of the _smaller parcels_ of
matter here upon the _Earth_, as that of _Fruits_, _Pebbles_, or _Flints_,
&c. (which seem to have been a _Liquor_ at first) may not be caused by the
_heterogeneous ambient fluid_. For thus we see that melted _Glass_ will be
naturally formed into a _round Figure_; so likewise any small Parcel of any
_fusible body_, if it be perfectly enclosed by the _Air_, will be driven
into a _globular_ Form; and, when cold, will be found a _solid Ball_. This
is plainly enough manifested to us by their way of making _shot_ with the
_drops of Lead_; which being a very pretty curiosity, and known but to a
very few, and having the liberty of publishing it granted me, by that
_Eminent Virtuoso_ Sir _Robert Moray_, who brought in this Account of it to
the _Royal Society_, I have here transcribed and inserted.