the prefs. He adds, that if by any fudden revolution of the laws of nature, or by any fortunate difcovery of those on the fpot, it has really become that fertile and profperous land, which fome reprefent it to be, he begs permiffion to add his voice to the general congratulation.'-The reader will at once perceive that this mode of joining in congratulation, is, perhaps, not the most graceful, and too much resembles thofe old-fashioned accompaniments to doubtful intelligence, hum! and ha!

Differtations on different Subjects in Natural Philofophy. By James Hutton, M. D. 4to. I. Is. Boards. Cadell.

1792.

WE

JE are not unacquainted with Dr. Hutton as a philofopher. In the Edinburgh Philofophical Tranfactions, he is the author of various differtations, which difplay at least diligence and attention; and are ingenious, if not fatisfactory. Dr. Hutton's Effay on the Theory of Rain, in the first volume of that collection, we noticed in our LXVIth volume, page 110, and there offered our reafons for thinking his fyftem in part gratuitous, and in part incomplete. This effay forms the firft Differtation in the prefent volume; and the second is a reply to the objections of M. de Luc, published in the Ideès fur la Meterologie, which have appeared in the fecond volume of the Edinburgh Tranfactions. M. de Luc, though poffeffed of no inconfiderable knowledge, is fo wordy an author, his grains of science are so much overwhelmed with chaff, that we have feldom been able to follow him in a controversy. The third Effay is connected with the former, and relates to winds, which are explained on foundations as uncertain, and on fuppofitions as hypothetical, as the phenomenon of rain. We fhall not, therefore, refume the fubject, but proceed to the other Differtations.

The fecond part treats of the principle of fire. It is the chemistry,' obferves our author in his Preface, of those meteors which give light and heat: it is the chemistry of that central heat, which actuates the mineral regions where our land is prepared; and it is the chemistry of that, which more immediately concerns us, in being the caufe of animal heat." An author, unacquainted with Dr. Hutton's works, would read this paragraph with fome aftonifhment; with admiration, tempered with fufpicion. To us the principal ideas were not new: they occurred in our author's Theory of the Earth, in the first volume of the Edinburgh Tranfactions, and were examined at no inconfiderable length, in our LXVIth volume, Page 115.

While Dr. Hutton was fupporting the principle of a central fire, and directing its powers in the performance of the most important operations, he muft feel feverely the ruin which threatened the whole, by the deftruction of its principal foundation, phlogiston. The tortoise must be supported, or the elephant, and its precious load, the earth, muft fall. Perhaps the system, in a proper view, might not be much endangered by the refult of the inquiry, whatever was the decifion; but our author wanders round it without any clear ideas—we must follow him. Inflammable bodies certainly differ from those which are uninflammable; but in what do they differ ?-do they poffefs only fenfible or latent heat, or do they derive, from the folar influence, another principle, by which they are dif tinguished? The object is to fhow, that there is another principle, and that this principle is the old, deferted phlogifton.

The modern term caloric, our author confiders to be heat either fenfible or latent; but the purpose of his

Paper is to show, that fome important facts, or effential phenomena in the burning bodies, are not explained in the antiphlogistic theory; and that, until these be explained, it must be neceffary to retain the term phlogifton, which expreffes fomething material in the knowledge of nature, or generalizes certain phenomena, which the new theory does not explain,

The doctrine of phlogifton may be confidered as implying, that a quantity of the matter of light and heat is occafionally contained in bodies, as a part of their compofition; and that those phlogistic bodies poffefs this naturally diffufive fubftance, upon a different principle from that of heat, or any other besides this which is peculiar to itself,

There is no question at prefent, how far this was precisely the idea of the chymifts who first introduced that term; or if, on many occafions, the term phlogifton has been mifapplied, before the nature of the feveral aeri-form compofitions was known. We have only in view, to endeavour to retain the term of phlogiston where it may be properly applied, and to fhow the defect of the new theory, which does not explain an important part of natural phenomena, or which rather attempts to explain it by a principle which will not apply.

We think his error is obvious from this statement. Caloric is not heat, either fenfible or latent. It is an abftra&t term for the matter of heat: in other words, the principle, in confequence of which heat is, or is capable of being, evolved from different bodies. It is clear, that the heat, produced in burning bodies, does not wholly arife from the body burnt, but from the furrounding air; that the change produced by burn

E 3

ing,

ing, is as much the confequence of the addition of one prin ciple, as of the abftraction of another; that no heat is con ferred by the folar influence, except fo far as it is conveyed by light. Independent of thefe confiderations, Dr. Hutton feems to mistake the principle, in difpute, between the old and the modern fchools of chemistry. The one fuppofed, like our author, a principle in bodies, the prefence of which rendered them inflammable, and its abfence uninflammable: the other fhowed that the pureft and leaft compound bodies were inflammable, and the most compounded in the oppofite state, so the confequence was, that burning confifted in the addition, rather than in the deprivation of any ingredient, and this addition they found to be air in a peculiar form. Again: our author endeavours to fhow, that his phlogiston is diftinct from every fpecies of heat, yet it only appears, fo far as we can perceive, by properties connected with the inflammable ftate. It is fuppofed alfo to be a peculiar modification of the folar fubftance, though we know nothing of folar influence, except as light, which it certainly imparts, and as fenfible heat, with which it is perhaps more remotely connected.

The two great difficulties which perplex our author, are the diftinction between heat, occasionally evolved, and latent heat; fecondly, the decompofition of water. He labours to explain the first with great care; and having fhown that heat fometimes evolved is not latent heat, while it certainly in its former ftate was not fenfible, it must be phlogifton. Dr. Crawford's work, with the Memoirs of M. Lavoifier, would foon explain the difficulty: latent heat is occafionally received and difcharged, with an alteration of form only :-the caloric, on the contrary, is an ingredient, on which the effential properties of bodies occafionally depend. The fecond difficulty we cannot elucidate, as it depends fo much on the nature of the experiment, every part of which Dr. Hutton mifapprehends. The compofition and decompofition of the fuppofed phlogifton, relate only to inflammable air, which the modern chemists have completely illuftrated.

.. The third part confifts of phyfical differtations on the pow -ers of matter and the appearances of bodies, chiefly tending to fupport the existence of the favourite phlogifton; and the first differtation is on the laws of matter and motion;-in other words, an inquiry into the nature of phyfical body, its conftitution, qualities, and accidents. Had our author purfued this fubject, without the bias of a theory, fcience might have gained by the inveftigation. Our ideas of matter, and of its different properties, require a new inveftigation, unfettered by the trammels of the old mechanical philofophy. It was too much the cultom of philofophers to confider matter in the

bulk

bulk, and too little in its minuter parts. On this fubject, our author's obfervations deferve notice.

But, before we proceed to investigate those powers of bodies by which their qualities may be changed, it will be proper, in the next differtation, to take a view of that general quality of bodies by which they naturally change their places in relation to each other, a quality which has been moft fuccefstully generalifed, although perhaps upon fome principles which, according to the theory of matter now to be given, cannot be admitted.

Therefore, before proceeding to that fubject, it will here be proper to mention those principles or opinions which are now alledged as having been improperly employed in generalising gravity. We shall thus have an opportunity, in this preliminary differtation, of examining certain fundamental principles of great importance in natural philofophy, principles which are to be employed in the following phyfical investigations.

First, then, the received philofophy fays, that matter, as the elementary fubitance of bodies, obeys the law of inertia. This doctrine, I apprehend, is either a mifapplication of the term inertia, or a misunderstanding of the term matter. One thing is certain; it is not in the maiter, which conftitutes natural bodies, that the law of inertia has been inveftigated, but in the bodies themselves. Therefore, fo far as there is a diftinction made of bodies and the matter of which those things are compofed, there is not any evidence of inertia being proper to the matter. It must alfo appear, that, so far as there is no diftinction made of bodies and their matter, there is no objection here intended to the ufe of the term inertia, as commonly understood.

Perhaps it may be thought that this is but a trifling difference, or a frivolous diftinction; and that, the law being acknowledged, it is of little confequence whether, in the expreffion of it, the term metter or body be employed, efpecially as philofophers feem to be fo little agreed about the diftinction of thole two things which, in this cafe, only form the fubject of dispute. To this it must be replied, that it is in forming the neceffary diftinction of matter and body, that the error of expreffion is difcovered; and that it draws to an important conclufion, when matter, as the principles or conftituent fubftance of bodies, comes to be inveftigated; for, perhaps, it may be found, that there exifts a certain fpecies of matter not subject to that law of inertia which we are to examine; perhaps it may be found, that no fpecies of matter, ftrictly speaking, is inert, as poffeffing that property which is fo confpicuous in bodies. But, in either of thefe cafes, natural philofophy muft appear to have proceeded upon a falfe principle, in having reafoned upon inertia as an univertal, in relation to matter as diftinguifhed from mind, or even as diftinguifhed from body.

'Secondly, the received philofophy fays, that all matter gravitates; for, having (gratuitoufly indéed) endowed all matter with the property of inertia, it is thus found, by an eafy experiment, that all the matter of a body muft have weight. But this is only faying, that the inertia of a body is in proportion to its gravitation. Now, this may truly be, without it neceffarily following, that all the matter which enters the conftitution of a body, fhould be actually endowed with inertia and weight. I hope that I have shown, in the preceding differtation, that all matter does not gravitate. But this is a point upon which hangs the fyftem of phyfics, which is to be propofed in the fubfequent differtations; and the truth of this alertion will therefore depend upon the confiftency of that fyftem with the natural appearances of things, or upon the explanation that may thus be given to the natural phenomena.'

We fully agree with Dr. Hutton, that inertia is a property of body; but we must add, that he has not shown inertia to be inconfiftent with matter. We certainly know nothing of matter, but as a divifible part of body; for, in the decompofition of compounds, we arrive at what, in any other situation, would be called body, and the minutest parts of elementary bodies ftill poffefs the fame properties. What therefore is predicated of the largeft, must be of the fmalleft portions, though the converse of the propofition is not true, fince the fmaller particles appear to be actuated by relative powers, though ftill obedient to the general ones. Thus the fmalleft particles of an acid and alkali, seem to be active in their mutual unions: the molecules of falts feem to unite by a predetermined election, yet they are ftill particles of matter, and each subjected to the law of gravity.

Dr. Hutton entangles himself alfo in difcuffions refpecting gravity. He forms the net by his definition, and proceeds with difficulty in the confufed outline. He feems willing to deny, that gravity is an univerfal principle, and expreffes himfelf in a manner at firft equivocal, with refpect to the extenfion of gravity to the celestial bodies. Gravity, he remarks, is that power by which a body feels heavy, when Jupported by the hand, or by which, when unfupported, it falls to the ground.'

This is an unfair view: gravity is only, on a larger fcale, the mutual attraction of bodies. Were the projectile force of the earth deftroyed, the fun and earth would unite by the force of gravity, but the point of meeting would be as near to the fun, as the fun is greater from the earth. Had our author followed this Newtonian view of the fubject, much of his future difcuffion might have been spared. We fhall notice only one paragraph:

More than one place in fpace being thus conceived, we acquire

the