tionable to the velocity, direction, and other affections of fuch motion?

We might farther afk alfo, by what means, and in what manner, this fuppofed accumulation of material fire is effected? Can the fimple collifion, or attrition, of two bodies in any direction, attract that Fire from every fide to the spot ? or are they only attracted in one direction? Infinite, indeed, are the objectiors that might be made to this fuppofition of Fire's exifting as a phyfical Being in every part of the univerfe we fhall proceed, therefore, to our Author's fecond propofition.

Prop. II. Pure Fire is a real body, and confifts of the moft fimple, folid, hard, fmooth, and smallest ele< mentary particles of all matter.'

In fupport of this affertion, Dr. Hillary appears greatly to depend on the authority of Boerhaave: but, with due deference to the character of that celebrated Chemist, we dare affirm, that no experiment he ever made, fufficiently proves the truth of it. His fuppofition, that because a red-hot fphere, fufpended in cold water, will diffufe its heat gradually to every part of that water, in proportion to the distance. from its furface, is no proof at all of the corporeal extenfion of fire. For, let heat be fuppofed to arife from the inteftine motion of bodies, and fuch a diffufion of heat will appear the neceffary confequence of the action of the component parts of the sphere on those of the water, which latter will be put in motion by the former, and that in fuch proportion to their diftance, as perfectly agrees with the experiment.

Our Author's reasoning, and experiments, to prove Fire a material body, are alfo as little conclufive.

• Notwithstanding (fays he) that Fire is fuch an exceeding fubtile being; yet when it is enquired into, in a suitable and proper manner, it may be rendered fo perceptible and evident to several of our fenfes, that it may be demonstrat<ed to be a real corporeal fubftance, or body.

burning; altho', in its ignited, glowing ftate, there is, perhaps, no great impropriety in terming it fo: for tho' a lighted coal be, as Sir Ifaac Newton fays, nothing but red hot wood, yet if the term Fre may be applied to any body, a lighted coal may be called fuch, with as much propriety as any other. But, philofophically speaking, Fire Is neither the wood, the coal, nor the afhes; but that which reduces the first gradually into the laft, and which we do not conceive to be in itself a body, but a fpecies of motion to which bodies are liable.

Firft, Fire is fomething that is extended, and fills fome • space, and may be moved from place to place; and confe

quently may be measured by geometrical lines; and can act < upon all other bodies with great power and force, and move 'with great velocity, &c. all which give us a true idea of what is called body; as the following experiments will • more fully prove.

Collect this pure Fire with a glafs globe, or an electrical machine, into a receiver, which is well lined or coated with a metallic fubftance, as in the ufual manner in fuch ' experiments; and let a wire of any metal be extended from near that receiver, to as great a diftance as you please, then let another wire be returned from near the end of the firft wire, and fo place as many wires to pafs forwards and back again, as you pleafe; let these wires be fo placed that ⚫ their ends may not touch, but come as near to each other as the one-fixth of an inch: then bring the end of the first wire, by the means of the machine, as ufual in this experiment, to touch the receiver; and the fire which is collected in it, will inftantly pafs along through all the wires ' with great velocity, and will jump over the ends from one wire to another, and fo on to and through all the wires ; and as it paffes or jumps over from one wire to another, it 'will give a visible flash of fire, and at the fame time make an audible noife or fnap: and if the wire is touched with the finger of a perfon not electrified, or who has a lefs pro❝ portion of fire in his body, the fire will pafs from the wire into his body, and give him a fmart ftroke or fhock; fo that he will both fee, hear, and feel the fire act upon his body or fenfes, as matter or body in motion acts upon us.

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By this experiment, it evidently appears, that Fire is a real body, which was collected in a confiderable great quantity into a certain given or circumfcribed fpace, which space it quitted, and paffed on into another space, and fo fucceffively on to many other places, as matter or body in motion does; and confequently must be a real fubftance: and that it is truly corporeal, is evident to no lefs than three of our fenfes, (though this has been denied by fome perfons, who at the fame time have readily acquiefced in knowing that many other things are, which only are perceived by one of our senses) but this fire, whilst it is thus in motion, may be clearly feen, diftinctly heard, and fenfibly felt, therefore it must be fomething that is really corporeal, and acts on our fenfes and bodies as matter or body acts.

Fire is not only thus demonftrated to be a body; but wę fhall make it appear to be a body compofed of the most fimple, folid, hard, fimooth, and the smallest elementary particles of all matter.'

For a reply to what Dr. Hillary here advances, respecting the paffage of the electric fire, we may refer our Readers to an article in a former Review*, wherein we have fhewn that the tranfition of any corporeal fubftance, or effluvia, along the furface, or through the pores of the wire, in electrical experiments, is merely imaginary.

Our Author, indeed, fays, that it is evident to no less than three of our fenfes, that this fire is truly corporeal. But if it be corporeal, it must have dimenfions; as length, breadth, and thickness. Are thefe feen, heard, or felt? The light it gives, according to this Writer's own fyftem, is not the fire itfelf; neither is the found it makes; nor doth the fenfation, arifing from the shock, at all refemble that of the refiftance of folid bodies: fo that this fire does not act on our fenfes, and bodies, as other bodies do. Yet light, found, and the fudden pain occafioned by the fhock, are all that is feen, heard, and felt: neither of which, we will be bold to fay, are themfelves bodies, but merely phenomena, or the apparent effects of the motion of bodies,

The inteftine motion of the fluid contained in the receiver, is, doubtless, in the above experiment, propagated through the wires, and communicated from one to the other; nor need we wonder that it is done with fo much force and velocity, if we reflect on a fimilar inftance in the cafe of found..

It is well known, that found is communicated by, and propagated thro', folid bodies, with a much greater velocity, and momentum, than thro' the air, or other fluids: for, if the ear be placed clofe to one end of a long ftick, or piece of timber, while the leaft noife be occafioned by a scratch, or blow, against the other, fuch noife will be very audibly heard; altho' by an ear placed at a lefs diftance from the end ftruck, if not applied to the timber, it would not be heard, at all.

Now Dr. Hillary may as well affert, from this experiment, that found is a material body, and actually paffes thro' the pores of the timber, as that the electric fire is corporeal, and pafles through the wire; becaufe, by affecting one end, it

See Review, vol. XX. in the article of Levet on Eleâricity," page 299, feq.

neceffarily

neceffarily affects the other. It is, however, moft palpably demonftrable, that Sound is nothing but a vibratory motion in the groffer atmosphere: and, perhaps, fuch the electric fire is in the ethereal, or univerfal medium of bodies. We must have, at leaft, more fatisfactory reasons than those of Boerhaave, or our Author, before we can fubfcribe to the opinion of Fire's being a folid material body.

On this fundamental propofition, however, depends almost all that Dr. Hillary has advanced about the Laws of Motion, and Properties of Fire: a propofition that is, in fact, invalidated by every other in this treatise.

In Propofition IV. we are told, that Pure elementary fire penetrates, pervades, rarifies, and expands all other bodies in the univerfe, both folid and fluid, which fall under the obfervation of our fenfes. And that this power is peculiar to fire only, and to no other body that we yet ⚫ know.'

To illuftrate this propofition, our Author makes the following obfervation.

Take a small folid bar of iron three feet long, let it be • exactly fitted to go into a cavity made in another bar of the fame metal, which is fomething longer than the firft, and let that longer end be graduated into the tenths of an inch. Then place the first bar oppofite to the fun till it is very · warm, the other bar remaining in a cold place; then put the warm bar into the cavity of the other bar, and you will ⚫ find it fo much extended longer, that it will not go into the cavity into which it eafily went before. Then ignite the firft bar red-hot, and place it again upon the cavity of the. other bar, it being ftill cold, and the firft bar will be found to be near five tenths, or half an inch longer than it was when it was cold,

This extenfion of the iron is folely made by the body of the fire infinuating itfelf into the vacuities between the conftituent elementary particles of the iron, and fo rarifying, dilating, and expanding them further from each other than they were before, whereby it increases the bulk of the iron, and makes it fill a greater space than it did before; for it ' is evident, that no other body but fire is here added to the iron.'

It is, indeed, true, as every one knows, that heat expands metals; but as their weight is not thereby increased, who can tell whether fuch expanfion be not owing rather to the'

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enlargement of the pores of fuch metals, than the infinuation of any foreign matter? At leaft, this we are certain of, that if any perfectly folid particles (fuch as the elementary ones of fire are fuppofed by our Author to be) fhould infinuate themselves into the pores of fuch metallic bodies, those pores must first be big enough to admit them; and if fo, how can those particles increase the bulk of fuch metals? It may be faid, perhaps, that they increase that bulk in forcing their way into the pores. But whence can their force, fo to infinuate themselves, arife, but from fome motion they must be fupposed to have been first put into? And if, after all, we are reduced to the neceffity of fuppofing motion given to these fuppofed elements, why may we not attribute this expansion, at once, to a motion, or increase of motion, in the conftituent parts of those bodies themselves? A fuppofition much lefs liable to objections.

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In Propofition V. it is faid, Pure Fire is a body without gravity; and has no more tendency to any one part of fpace than any other.'

Having already denied Fire to be a body, we can readily agree to its having no gravity: altho' moft of thofe Philofophers who have taken the fame fide of the queftion with our Author, as to its being corporeal, have pretended to prove the truth of their opinion, by afferting it had weight. We fhall take leave, however, of our Phyfiologift's Propofitions, with obferving only one error more, which he seems to have fallen into for want of fo intimate a knowlege of his subject as he flatters himself to have acquired.

• Collect the rays of the fun,' fays he, with a large concave fpeculum, as that of Villet, into its focus, and there you will have the greatest and hottest degree of fire human art has yet been able to produce.' Again, in another place he tells us, there would be, 7396 times more fire in that focus than in an equal space in the circumambient air, heated by the fun at the fame time.' In fact, however, the air in that focus would not be hotter than the circumambient air, notwithstanding it be very true, that bricks and ftones placed therein, would be vitrified, or metals put in fufion in a moment. If our Author doubts of this, let him repeat the fimple experiments mentioned by the late ingenious Mr. Melvil, and he will be convinced of it,

* See Phyfical and Literary Effays, of the Edinburgh Society, vol. II. page 23

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