Micrographia Part 2

That which makes the Lawn so transparent, is by the _Microscope_, nay by the naked eye, if attentively viewed, plainly enough evidenced to be the mult.i.tude of square holes which are left between the threads, appearing to have much more hole in respect of the intercurrent parts then is for the most part left in a _lattice-window_, which it does a little resemble, onely the crossing parts are round and not flat.

These threads that compose this fine contexture, though they are as small as those that const.i.tute the finer sorts of Silks, have notwithstanding nothing of their glossie, pleasant, and lively reflection. Nay, I have been informed both by the Inventor himself, and several other eye-witnesses, that though the flax, out of which it is made, has been (by a singular art, of that excellent Person, and n.o.ble Vertuoso, M. _Charls Howard_, brother to the _Duke of Norfolk_) so curiously dress'd and prepar'd, as to appear both to the eye and the touch, full as _fine_ and as _glossie_, and to receive all kinds of colours, as well as Sleave-Silk; yet when this Silken Flax is twisted into threads, it quite loseth its former l.u.s.ter, and becomes as plain and base a thread to look on, as one of the same bigness, made of common Flax.

The reason of which odd _Phenomenon_ seems no other then this; that though the curiously drest Flax has its parts so exceedingly small, as to equallize, if not to be much smaller then the clew of the Silk-worm, especially in thinness, yet the differences between the figures of the const.i.tuting filaments are so great, and their substances so various, that whereas those of the _Silk_ are _small_, _round_, _hard_, _transparent,_ and to their bigness proportionably _stiff_, so as each filament preserves its proper _Figure_, and consequently its vivid _reflection_ intire, though twisted into a thread, if not too hard; those of Flax are _flat_, _limber_, _softer,_ and _less transparent_, and in twisting into a thread they joyn, and lie so close together, as to lose their own, and destroy each others particular reflections. There seems therefore three Particulars very requisite to make the so drest Flax appear Silk also when spun into threads. First, that the substance of it should be made more _clear_ and _transparent_, Flax retaining in it a kind of opacating brown, or yellow; and the parts of the whitest kind I have yet observ'd with the _Microscope_ appearing white, like flaw'd Horn or Gla.s.s, rather then clear, like clear Horn or Gla.s.s. Next that, the filaments should each of them be _rounded_, if that could be done, which yet is not so very necessary, if the first be perform'd, and this third, which is, that each of the small filaments be _stifned_; for though they be square, or flat, provided they be _transparent_ and stiff, much the same appearances must necessarily follow.

Now, though I have not yet made trial, yet I doubt not, but that both these proprieties may be also induc'd upon the Flax, and perhaps too by one and the same Expedient, which some trials may quickly inform any ingenious attempter of, who from the use and profit of such an Invention, may find sufficient argument to be prompted to such Inquiries. As for the _tenacity_ of the substance of Flax, out of which the thread is made, it seems much inferiour to that of Silk, the one being a _vegetable_, the other an _animal_ substance. And whether it proceed from the better concoction, or the more h.o.m.ogeneous const.i.tution of _animal_ substances above those of _vegetables_, I do not here determine; yet since I generally find, that _vegetable_ substances do not equalize the _tenacity_ of _animal_, nor these the _tenacity_ of some purified _mineral_ substances; I am very apt to think, that the _tenacity_ of bodies does not proceed from the _hamous_, or _hooked_ particles, as the _Epicureans_ and some modern _Philosophers_ have imagin'd; but from the more exact _congruity_ of the const.i.tuent parts, which are contiguous to each other, and so bulky, as not to be easily separated, or shatter'd, by any small pulls or concussion of heat.

Observ. IV. _Of fine waled Silk, or Taffety._

This[5] is the appearance of a piece of very fine Taffety-riband in the bigger magnifying Gla.s.s, which you see exhibits it like a very convenient substance to make Bed-matts, or Door-matts of, or to serve for Beehives, Corn-scuttles, Chairs, or Corn-tubs, it being not unlike that kind of work, wherewith in many parts in _England_, they make such Utensils of Straw, a little wreathed, and bound together with thongs of Brambles. For in this Contexture, each little filament, fiber, or clew of the Silk-worm, seem'd about the bigness of an ordinary Straw, as appears by the little irregular pieces, ab, cd, and ef; The _Warp_, or the thread that ran crossing the Riband, appear'd like a single Rope of an Inch Diameter; but the _Woof_, or the thread that ran the length of the Riband, appear'd not half so big.

Each Inch of six-peny-broad Riband appearing no less then a piece of Matting Inch and half thick, and twelve foot square, a few yards of this, would be enough to floor the long Gallery of the _Loure_ at _Paris_. But to return to our piece of Riband: It affords us a not unpleasant object, appearing like a bundle, or wreath, of very clear and transparent _Cylinders_, if the Silk be white, and curiously ting'd; if it be colour'd, each of those small horney _Cylinders_ affording in some place or other of them, as vivid a reflection, as if it had been sent from a _Cylinder_ of Gla.s.s or Horn. In-so-much, that the reflexions of Red, appear'd as if coming from so many _Granates_, or _Rubies_. The loveliness of the colours of Silks above those of hairy Stuffs, or Linnen, consisting, as I else-where intimate, chiefly in the transparency, and vivid reflections from the _Concave_, or inner surface of the _transparent Cylinder_, as are also the colours of Precious Stones; for most of the reflections from each of these _Cylinders_, come from the _Concave_ surface of the air, which is as 'twere the foil that incompa.s.ses the _Cylinder_. The colours with which each of these _Cylinders_ are ting'd, seem partly to be superficial, and sticking to the out-sides of them; and partly, to be imbib'd, or sunck into the substance of them: for Silk, seeming to be little else then a dried thread of Glew, may be suppos'd to be very easily relaxt, and softened, by being steeped in warm, nay in cold, if penetrant, juyces or liquors. And thereby those tinctures, though they tinge perhaps but a small part of the substance, yet being so highly impregnated with the colour, as to be almost black with it, may leave an impression strong enough to exhibite the desir'd colour. A pretty kinde of artificial Stuff I have seen, looking almost like transparent Parchment, Horn, or Ising-gla.s.s, and perhaps some such thing it may be made of, which being transparent, and of a glutinous nature, and easily mollified by keeping in water, as I found upon trial, had imbib'd, and did remain ting'd with a great variety of very vivid colours, and to the naked eye, it look'd very like the substance of the Silk. And I have often thought, that probably there might be a way found out, to make an artificial glutinous composition, much resembling, if not full as good, nay better, then that Excrement, or whatever other substance it be out of which, the Silk-worm wire-draws his clew. If such a composition were found, it were certainly an easie matter to find very quick ways of drawing it out into small wires for use. I need not mention the use of such an Invention, nor the benefit that is likely to accrue to the finder, they being sufficiently obvious. This hint therefore, may, I hope, give some Ingenious inquisitive Person an occasion of making some trials, which if successfull, I have my aim, and I suppose he will have no occasion to be displeas'd.

Observ. V. _Of watered Silks, or Stuffs._

There are but few _Artificial_ things that are worth observing with a _Microscope_, and therefore I shall speak but briefly concerning them. For the Productions of art are such rude mis-shapen things, that when view'd with a _Microscope_, is little else observable, but their deformity. The most curious Carvings appearing no better then those rude _Russian_ Images we find mention'd in _Purchas_, where three notches at the end of a Stick, stood for a face. And the most smooth and burnish'd surfaces appear most rough and unpolisht: So that my first Reason why I shall add but a few observations of them, is, their mis-shapen form; and the next, is their uselessness. For why should we trouble our selves in the examination of that form or shape (which is all we are able to reach with a _Microscope_) which we know was design'd for no higher a use, then what we were able to view with our naked eye? Why should we endeavour to discover mysteries in that which has no such thing in it? And like _Rabbins_ find out _Caballisms_, and _aenigmas_ in the Figure, and placing of Letters, where no such thing lies hid: whereas in _natural_ forms there are some so small, and so curious, and their design'd business so far remov'd beyond the reach of our sight, that the more we magnify the object, the more excellencies and mysteries do appear; And the more we discover the imperfections of our senses; and the Omnipotency and Infinite perfections of the great Creatour.

I shall therefore onely add one or two Observations more _artificial_ things, and then come to the Treaty concerning such matters as are the Productions of a more curious Workman. One of these, shall be that of a piece of water'd Silk, represented in the second Figure of the third _Scheme_,[6] as it appear'd through the least magnifying Gla.s.s. _AB_ signifying the long way of the Stuff, and _CD_ the broad way. This Stuff, if the right side of it be looked upon, appears to the naked eye, all over so waved, undulated, or grain'd, with a curious, though irregular variety of brighter and darker parts, that it adds no small gracefulness to the Gloss of it. It is so known a propriety, that it needs but little explication, but it is observable, which perhaps everyone has not considered, that those parts which appear the darker part of the wave, in one position to the light, in another appears the lighter, and the contrary; and by this means the undulations become transient, and in a continual change, according as the position of the parts in respect of the incident beams of light is varied. The reason of which odd _phaenomena_, to one that has but diligently examin'd it even with his naked eye, will be obvious enough. But he that observes it with a _Microscope_, may more easily perceive what this _Proteus_ is, and how it comes to change its shape. He may very easily perceive, that it proceeds onely from the variety of the _Reflections_ of light, which is caus'd by the various _shape of the Particles_, or little protuberant parts of the thread that compose the surface; and that those parts of the waves that appear the brighter, throw towards the eye a mult.i.tude of small reflections of light, whereas the darker scarce afford any. The reason of which reflection, the _Microscope_ plainly discovers, as appears by the Figure. In which you may perceive, that the brighter parts of the surface consist of an abundance of large and strong reflections, denoted by a, a, a, a, a, &c. for the surfaces of those threads that run the _long way_, are by the Mechanical process of watering, _creas'd_ or _angled_ in another kind of posture then they were by the weaving: for by the weaving they are onely _bent round_ the warping threads; but by the watering, they are _bent with an angle, or elbow_, that is in stead of lying, or being bent _round_ the threads, as in the third Figure, a, a, a, a, a, are about b, b, b (b, b, b representing the ends, as 'twere, of the cross threads, they are bent about) they are creas'd on the top of those threads, with an _angle_, as in the fourth Figure, and that with all imaginable variety; so that, whereas before they reflected the light onely from one point of the round surface, as about c, c, c, they now when water'd, reflect the beams from more then half the whole surface, as de, de, de, and in other postures they return no reflections at all from those surfaces. Hence in one posture they compose the brighter parts of the waves, in another the darker. And these reflections are also varied, according as the particular parts are variously bent. The reason of which creasing we shall next examine; and here we must fetch our information from the Mechanism or manner of proceeding in this operation; which, as I have been inform'd, is no other then this.

They double all the Stuff that is to be water'd, that is, they crease it just through the middle of it, the whole length of the piece, leaving the right side of the Stuff inward, and placing the two edges, or silvages just upon one another, and, as near as they can, place the wale so in the doubling of it, that the wale of the one side may lie very near parallel, or even with the wale of the other; for the nearer that posture they lie, the greater will the watering appear; and the more obliquely, or across to each other they lie, the smaller are the waves. Their way for folding it for a great wale is thus: they take a Pin, and begin at one side of the piece in any wale, and so moving it towards the other side, thereby direct their hands to the opposite ends of the wale, and then, as near as they can, place the two opposite ends of the same wale together, and so double, or fold the whole piece, repeating this enquiry with a Pin at every yard or two's distance through the whole length; then they sprinkle it with water, and fold it the longways, placing between every fold a piece of Pastboard, by which means all the wrong side of the water'd Stuff becomes flat, and with little wales, and the wales on the other side become the more protuberant; whence the creasings or angular bendings of the wales become the more perspicuous. Having folded it in this manner, they place it with an interjacent Pastboard into an hot Press, where it is kept very violently prest, till it be dry and stiff; by which means, the wales of either contiguous sides leave their own impressions upon each other, as is very manifest by the second Figure, where 'tis obvious enough, that the wale of the piece ABCD runs parallel between the p.r.i.c.ked lines ef, ef, ef, and as manifest to discern the impressions upon these wales, left by those that were prest upon them, which lying not exactly parallel with them, but a little athwart them, as is denoted by the lines of, oooo, gh, gh, gh, between which the other wales did lie parallel; they are so variously, and irregularly creas'd that being put into that shape when wet, and kept so till they be drie, they so let each others threads, that the Moldings remain almost as long as the Stuff lasts.

Hence it may appear to any one that attentively considers the Figure, why the parts of the wale a, a, a, a, a, a, should appear bright; and why the parts b, b, b, b, b, b, b, should appear shadowed, or dark; why some, as d, d, d, d, d, d, should appear partly light, and partly dark: the varieties of which reflections and shadows are the only cause of the appearance of watering in Silks, or any other kind of Stuffs.

From the variety of reflection, may also be deduc'd the cause why a small breez or gale of wind ruffling the surface of a smooth water, makes it appear black; as also, on the other side, why the smoothing or burnishing the surface of whitened Silver makes it look black; and mult.i.tudes of other phaenomena might hereby be solv'd, which are too many to be here insisted on.

Observ. VI. _Of Small Gla.s.s Canes._

That I might be satisfied, whether it were not possible to make an _Artificial_ pore as _small_ as any _Natural_ I had yet found, I made several attemps with small _gla.s.s 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 gla.s.s, 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 gla.s.s; and so easily distingish, without seeing either end, whether any _Cylinder_ of gla.s.s 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 gla.s.s, 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 gla.s.s, 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 _a.s.siduity_ 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 inc.u.mbent 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 Gla.s.s _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 Gla.s.s, 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 _aether_, 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 quant.i.ty, as may be found by _praecipitations_, 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 aether_, may disperse and _expand_ it self into a _vast s.p.a.ce_, if it have room enough, and infect, as it were, every part of that s.p.a.ce. 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 _rarfy'd state_ to fill some _hundred thousand_ s.p.a.ces of aether, 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 _praecipitation_, as we are able to _separate_ the Air from the aether by _Gla.s.s_, and several other bodies. And though we are yet unable and ignorant of the ways of _praecipitating_ Air out of the aether 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 _praecipitating_ 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 _circ.u.mstances_ 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, dest.i.tute both of a _Compa.s.s_ and the sight of the _Celestial guids_, 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 _gla.s.s 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 [Mercury], _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 _Cohaesion_ 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_, _Gla.s.s_, &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 _h.o.m.ogeneal 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 Gla.s.s, 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 _aether_ 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 s.p.a.ce 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 _advent.i.tious_ 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 encompa.s.sing 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 _p.r.i.c.ked 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 incompa.s.sed _fluid_ towards the incompa.s.sing 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 _Gla.s.s Jar_) Let FGEMM represent a contain'd _fluid_, as water; this towards the bottom and sides, is figured according to the concavity of the _Gla.s.s_: 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 Gla.s.s) 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 Gla.s.s 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 Gla.s.s 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 Gla.s.s, and const.i.tutes 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 Gla.s.s 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-gla.s.s, 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 _Gla.s.s_ is more incongruous then _Air_ (and thereby being put into a _Gla.s.s-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 _advent.i.tious 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 _protusion_ against _the concave_ or inner side of the _Spring_; So to alter this _spherical_ const.i.tution 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 protude 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 _Gla.s.s-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 _pa.s.sage_ or _hole_ at the top, into which may be fastened with _cement_ several _small Pipes_ of determinate _cylindrical_ cavities: as let _hollow_ of

F. 1/4 G. 1/6 H. 1/8 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 quant.i.ties, 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 f.a.ggot-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 pa.s.sage 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 pa.s.sage 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_; therefore is probably the princ.i.p.al (if not the only) cause of these _Phaenomena_.

This therefore being thus explained, there will be divers _Phaenomena_ 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 _Gla.s.s_, 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 pa.s.sing of it out of the earth into their roots. And indeed upon the consideration of this Principle, mult.i.tudes 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 _Gla.s.s_ then _Air_, and _Air_ then _Quicksilver_: whence an _oblique Ray_ out of _Gla.s.s_, will pa.s.s into _water_ with very little _refraction_ from the _perpendicular_, but none out of _Gla.s.s_ into _Air_, excepting a _direct_, will pa.s.s 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 const.i.tution, from that of _Air_, _Water_, _Gla.s.s_, &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 Gla.s.s 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 _Phaenomena_ 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 _Gla.s.s_, 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 _circ.u.m-ambient fluid aether_? 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 _Gla.s.s_ 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 quant.i.ty you please, melt it down, stir and clear it with an iron Ladle, gathering together the blackish parts that swim at top like sc.u.m, and when you see the colour of the clear Lead to be greenish, but no sooner, strew upon it _Auripigmentum_ powdered according to the quant.i.ty 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 Gla.s.s, 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._

_While 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 it 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 it 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._