Chapter 7

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.

To make small shot of different sizes; Communicated by his Highness _P.R._

_Take Lead out of the Pig what quantity you please, melt it down, stir and clear it with an iron Ladle, gathering together the blackish parts that swim at top like scum, and when you see the colour of the clear Lead to be greenish, but no sooner, strew upon it _Auripigmentum_ powdered according to the quantity of Lead, about as much as will lye upon a half Crown piece will serve for eighteen or twenty pound weight of some sorts of Lead; others will require more, or less. After the _Auripigmentum_ is put in, stir the Lead well, and the _Auripigmentum_ will flame: when the flame is over, take out some of the Lead in a Ladle having a lip or notch in the brim for convenient pouring out of the Lead, and being well warmed amongst the melted Lead, and with a stick make some single drops of Lead trickle out of the Ladle into water in a Glass, which if they fall to be round and without tails, there is _Auripigmentum_ enough put in, and the temper of the heat is right, otherwise put in more. Then lay two bars of Iron (or some more proper Iron-tool made on purpose) upon a Pail of water, and place upon them a round Plate of Copper, of the size and figure of an ordinary large Pewter or Silver Trencher, the hollow whereof is to be about three inches over, the bottom lower then the brims about half an inch, pierced with thirty, forty, or more small holes; the smaller the holes are, the smaller the shot will be; and the brim is to be thicker then the bottom, to conserve the heat the better._

_The bottom of the Trencher being some four inches distant from the water in the Pail, lay upon it some burning Coles, to keep the Lead melted upon it. Then with the hot Ladle take Lead off the Pot where it stands melted, and pour it softly upon the burning Coles over the bottom of the Trencher, and it will immediately run through the holes into the water in small round drops. Thus pour on new Lead still as fast as it runs through the Trencher till all be done; blowing now and then the Coles with hand-Bellows, when the Lead in the Trencher cools so as to stop from running._

_Whilst one pours on the Lead, another must, with another Ladle, thrusted four or five inches under water in the Pail, catch from time to time some of the shot, as it drops down, to see the size of it, and whether there be any faults in it. The greatest care is to keep the Lead upon the Trencher in the right degree of heat; if it be too cool, it will not run through the Trencher, though it stand melted upon it; and this is to be helped by blowing the Coals a little, or pouring on new Lead that is hotter: but the cooler the Lead, the larger the Shot; and the hotter, the smaller; when it is too hot, the drops will crack and fly; then you must stop pouring on new Lead, and let it cool; and so long as you observe the right temper of the heat, the Lead will constantly drop into very round Shot, without so much as one with a tail in many pounds._

_When all is done, take your Shot out of the Pail of water, and put it in a Frying-pan over the fire to dry them, which must be done warily, still shaking them that they melt not; and when they are dry you may separate the small from the great, in Pearl Sives made of Copper or Lattin let into one another, into as many sizes at you please. But if you would have your Shot larger then the Trencher makes them, you may do it with a Stick, making them trickle out of the Ladle, as hath been said._

_If the Trencher be but toucht a very little when the Lead stops from going through it, and be not too cool, it will drop again, but it is better not to touch it at all. At the melting of the Lead take care that there be no kind of Oyl, Grease, or the like, upon the Pots, or Ladles, or Trencher._

_The Chief cause of this Globular Figure of the Shot, seems to be the _Auripigmentum_; for, as soon as it is put in among the melted Lead, it loses its shining brightness, contracting instantly a grayish film or skin upon it, when you scum it to make it clean with the Ladle. So that when the Air comes at the falling drop of the melted Lead, that skin constricts them every where equally: but upon what account, and whether this be the true cause, is left to further disquisition._

Much after this same manner, when the Air is exceeding cold through which it passes; do we find the drops of Rain, falling from the Clouds, congealed into round Hail-stones by the freezing Ambient.

To which may be added this other known Experiment, That if you gently let fall a drop of _water_ upon small _sand_ or _dust_, you shall find, as it were, an artificial _round stone_ quickly generated. I cannot upon this occasion omit the mentioning of the strange kind of _Grain_, which I have observed in a _stone_ brought from _Kettering_ in _Northamptonshire_, and therefore called by Masons _Kettering-Stone_, of which see the Description. Which brings into my mind what I long since observed in the fiery Sparks that are struck out of a Steel. For having a great desire to see what was left behind, after the Spark was gone out, I purposely struck fire over a very white piece of Paper, and observing diligently where some conspicuous sparks went out, I found a very little black spot no bigger then the point of a Pin, which through a _Microscope_ appeared to be a perfectly round Ball, looking much like a polisht ball of Steel, insomuch that I was able to see the Image of the window reflected from it. I cannot here stay (having done it more fully in another place) to examine the particular Reasons of it, but shall only hint, that I imagine it to be some small parcel of the Steel, which by the violence of the motion of the stroke (most of which seems to be imprest upon those small parcels) is made so glowing hot, that it is melted into a _Vitrum_, which by the ambient Air is thrust into the form of a Ball.

A Fifth thing which I thought worth Examination was, Whether the motion of all kind of Springs, might not be reduced to the Principle whereby the included _heterogeneous fluid_ seems to be moved; or to that whereby two Solids, as Marbles, or the like, are thrust and kept together by the _ambient fluid_.

A Sixth thing was, Whether the Rising and Ebullition of the Water out of Springs and Fountains (which lie much higher from the Center of the Earth then the Superficies of the Sea, from whence it seems to be derived) may not be explicated by the rising of Water in a smaller Pipe: For the Sea-water being strained through the Pores or Crannies of the Earth, is, as it were, included in little Pipes, where the pressure of the Air has not so great a power to resist its rising: But examining this way, and finding in it several difficulties almost irremovable, I thought upon a way that would much more naturally and conceivably explain it, which was by this following Experiment: I took a Glass-Tube, of the form of that described in the sixth Figure, and chusing two _heterogeneous fluids_, such as Water and Oyl, I poured in as much Water as filled up the Pipes as high as AB, then putting in some Oyl into the Tube AC, I deprest the superficies A of the Water to F, and B I raised to G, which was not so high perpendicularly as the superficies of the Oyl F, by the space FI, wherefore the proportion of the gravity of these two Liquors was as GH to FE.

This Experiment I tried with several other Liquors, and particularly with fresh Water and Salt (which I made by dissolving Salt in warm Water) which two though they are nothing heterogeneous, yet before they would perfectly mix one with another, I made trial of the Experiment: Nay, letting the Tube wherein I tried the Experiment remain for many dayes, I observed them not to mix; but the superficies of the fresh was rather more then less elevated above that of the Salt. Now the proportion of the gravity of Sea-water, to that of River-water, according to _Stevinus_ and _Varenius_, and as I have since found pretty true by making trial my self, is as 46. to 45. that is, 46. Ounces of the salt Water will take up no more room then 45. of the fresh. Or reciprocally 45 pints of salt-water weigh as much as 46 of fresh.