of the vapour, being exposed to the action of the air, is burning rapidly.

II. We fhall now enter more fully into fome of the general inferences deduced by Count Rumford from the foregoing experiments. We have already hinted at feveral objections to one of his theories; we fhall prefently find, however, that the work teems with many abfurdities ftill more glaring.

In expounding his peculiar theory of heat, our author begins by remarking, that there is no fuch thing as reft in the univerfe that all the bodies of which we have any knowledge are in a state of motion--and that probably the particles of those bodies are alfo moving among themfelves. He then fuppofes the cafe of a perfectly elastic bell being ftruck while furrounded by other elaftic bodies in an elastic medium, and conceives that if the vibrations of the bell were more rapid than thofe of the other bodies, an equilibrium would take place; that if all the bodies were in equal vibration, no effect would be produced by their mutual actions; and that if the bell's vibrations were flower, they would gradually be increafed. This he thinks is a cafe ex actly fimilar to that of calorific and frigorific radiation; and as we, on the other hand, are convinced that a better expofition of his doctrine of vibrations could not be imagined, than the one prefented by purfuing this illuftration, and comparing it with our author's inference, we fhall give his application in his own words.

The rapid undulations occafioned in the furrounding ethereal fluid by the fwift vibrations of the hot body, will act as calorific rays on the neighbouring colder folid bodies; and the flower undulations occafioned by the vibrations of thofe colder bodies will act as frigorific rays on the hot body; and these reciprocal actions will continue, but with decreafing intenfity, till the hot body and thofe colder bodies which furround it fhall, in confequence of thefe actions, have become of the fame temperature, or until their vibrations have become ifochronous.

6

According to this hypothefis,' he adds, cold can with no more propriety be confidered as the abfence of heat, than a low or a grave found can be confidered as the abfence of a higher or more acute note; and the admiffion of rays which generate cold, involves no abfurdity, and creates no confufion of ideas.' p. 157.

Nothing, in our apprehenfion, could have more demonftratively fhown the fallacy of the author's whole theory than this illuftration and application. If frigorific rays are to be confidered as exifting fubftances, of a nature effentially different from calorific rays, what can be lefs applicable than the cafe of vibrations differing from other vibrations only in degree of ftrength? A frigorific ray can never, according to Count Rumford's theory, produce any of the effects of a calorific ray, modify either as

you

you pleafe. But a flow undulation refembles a quick one in every particular, and produces all the fame effects in a fmaller degree. A frigorific ray can never become calorific by any change: A flow undulation becomes a quick one by the eafieft tranfition imaginable. If words have any meaning, it is impoffible to draw the line between quick and flow undulations; for these terms are merely expreffions of a mutual relation. But furely nothing can be more definite than the boundary between pofitive heat and pofitive cold, according to our author's doctrine. Suppofe a quickly vibrating body is brought into the neighbourhood of a quiefcent one, the vibrations of the former will be diminished. If it be brought into the neighbourhood of a body vibrating flower than itself, its vibrations will still be diminished, but not fo much as if the second body had no motion at all. But will a hot body be more cooled by the neighbourhood of a body radiating neither heat nor cold, than by the neighbourhood of one radiating cold? The propofition is a contradiction in terms.

It also deserves to be confidered how Count Rumford introduces an ethereal fluid into his theory, filently, and without giving his readers any warning of fuch a poftulate. It is true that, without it, he cannot proceed a step; yet furely fo extravagant a demand fhould have been explicitly stated, instead of being tacitly affumed. But it appears to us, that the ether never was introduced with lefs felicity. When the existence of certain fubstances has been admitted; when, for example, Sir Ifaac Newton proceeded upon the pofition that the rays of light are folid particles of matter, acting on and affected by other parts of matter (a pofition which he had himself confirmed by his difcoveries), it was then fufficiently confiftent to confider how fuch material particles would affect, or be affected by, a furrounding medium like the fubtile ether, supposing such a fluid to exift. But, in the prefent cafe, the whole queftion relates to exiflence; the matter in difpute is the reality of heat or of cold, or of both, or of neither. To fettle this point, our author fancies an ether; he introduces a nonentity as a step in his reafonings upon the existence of other bodies. We are difcuffing the fubject, whether caloric is a fubftance? Count Rumford tells us he can fettle that queftion; and he begins his decifion by faying, for the ether.' What ether? He cannot tell. But fuppofe an ether. Why not fuppofe a caloric-the point at iffue? and then we are at least pared the labour of all his prolix and ufelefs argumentation.

Let us, however, admit this important preliminary, and fee whether the clumfy theory has even the paltry merit of explaining the phænomena: On the contrary, it is hardly reconcileable to a fingle fact. We fhall only take a few fpecimens of its powers in

this way.

If heat confifts in the internal motions of the particles of bodies, the question immediately occurs, how do bodies, by any. modifications of fuch motions, change their ftate from folidity to fluidity? and how does the idea of motion accommodate itself to the fact of heat being absorbed in fufion, afterwards to be given out again upon the body refuming the folid form. Count Rumford explains this in the following ftrange manner. We choose to quote his own words, left our readers fhould be difpofed to difbelieve any abridgement which imputed fuch opinions to an author of his note.

Whatever may be the figures of the orbits which the particles of a liquid defcribe, the mean diftances of these particles from each other remain the fame as when they conftituted a folid, as appears by the finall change of specific gravity which takes place when a folid is melted and becomes a liquid; and, on a fuppofition that their motions are regulated by the fame laws which regulate the folar fyftem, it is evident that the additional motion they muit neceffarily acquire, in order to their taking the fluid form, cannot be loft, but must continue to refide in the liquid, and muft again make its appearance when the liquid changes its form and becomes a folid.

It is well known,' he continues, that a certain quantity of heat is requifite to melt a folid; which quantity disappears or remains latent in the liquid produced by that procefs; and that the fame quantity of heat reappears when this fluid is congealed and becomes a folid body.' р. 1бо.

A certain quantity of motion abforbed, remaining latent, and then after an interval reappearing! What is abforbed, or latent, or quiefcent motion? Is it not reft? and what power can put particles into an intermitting motion, that is, a motion to be fufpended, and then to be revived again, without any new impulfe? Have we not here only a choice of impoffibilities and contradictions—either that motion is fomething which may be concealed and then developed, i. e. may remain at reft-or that, after being annihilated, it may be regenerated, without any new impulfe, i. e. may be produced anew without a caufe? Indeed, the confufion of ideas which pervades the whole of this explanation, is not only like, it is exactly the fame, with that which Swift has ridiculed in his picture of the Laputan projector, who wafted his life in extracting fun-beams from cucumbers, in order to preferve the rays for ufe during winter;-and with a ftill more palpable abfurdity that has become matter of common ridicule, the cold which froze up men's words, until, at the approach of fpring, the fpeeches made during winter began to thaw of themselves.

But it is not only in the more abftrufe parts of the theory of heat that Count Rumford's explanation fo miferably fails,-it is equally inadequate to account for the most ordinary appearances, although,

although, here, its difcrepancy with the facts may not at first fight appear fo palpable. Let us fee how it is reconciled with the expanfive power of caloric.

So long, according to our author, as the internal and inceffant motions among the particles of bodies remain the fame, no fenfible alteration can take place in their qualities or appearance. But when the radiations of hotter bodies, that is, the impulfes of pare ticles moving more rapidly, communicate to the former fubftances a greater degree of internal motion, their particles must vibrate more rapidly; the arches of their undulations must be elongated, and the vifible magnitude of the whole maffes increased. In like manner, if the bodies are cooled, that is, if their motions are diminished, the undulations will be contracted, and the vo lume of the masses diminished.

Now, furely, it seems obvious to answer, that if the increase of volume were produced entirely by an augmented vibration, it would be much eafier than we actually find it, to prevent, by external preffure, the expansion of a heated body. If the force were exerted not fteadily in one direction, from the centre to the furface of the body, but alternately and equally backwards and forwards, a very little compreffion would fuffice to stop this vi bration. Befides, the appearance of a body vibrating in this manner, however rapidly, would certainly be very different from that of a body gradually and steadily expanded in all its dimensions by heat. But two confiderations are of themselves quite fufficient to overthrow the whole of this reafoning.

In the first place, it is admitted that heat expands bodies equally in all directions. But vibratory motions can take place only in the directions determined by the initial impulfes; the wave muk always be in the plane of the line in which the firft ftroke is communicated to the undulating body. According, therefore, as heat is radiated in one line or another, we might expect to fee the dimenfions of the heated body expanded in one direction or another. It would always be, poffible, too, by oppofing oppofite forces, to counteract the effects of thofe impulfes; that is to fay, it would be poffible to ftop the vibrations by oppofite radiation, or to prevent the body from expanding by the application of more heat. We do not here ftop to inquire how this theory may be accommodated to the anomalous effects of cold in expanding certain bodies, as water and ice.

Secondly, If we attend to the nature of elafticity, and the laws of percuffion, we fhall be completely fatisfied that all this theory of motion is utterly unfounded; and the argument which we are now about to fuggeft, is fubmitted as one that must be decifive even with Count Rumford himself. Suppofe a radiation to acce

lerate

lerate the vibratory motion of a central particle, and of course to propagate its impulfe through the line of fucceffive particles, at the extremity of which this one first ftruck is fituated; let us confider what must neceffarily take place. The whole row of particles are actuated by an impulfe. But fuppofe, first, that only one impulfe is communicated; the particles being all elaftic by the hypothefis, the motion vifibly affects none but the laft. If a number of ivory or glafs balls are suspended by separate threads in a ftraight line, and apparently touching each other, and the ball at one end is made to vibrate against the one next in fucceffion, the whole line will remain unmoved, except the ball at the other extremity, which will fly off with the whole impulfe. This is a well known confequence of the common laws of percuffion, and the experiment is perfectly familiar to every one. If, inftead of one impulie, a conftant fucceffion of impulfes be communis cated to the first ball, or to each of the others; ftill the fame confequence follows, only the laft ball flies off with greater force, viz. with the accumulated force of all the impulfes, while the other balls remain at rest as before. Precifely the fame confe. quence must follow, if the number of the balls is indifinitely increased, their diameters diminished, and their neutral contact rendered more clofe. We have now exactly the line of particles first fuppofed in the heated body; and the radiation must produce the fame effect, according to Count Rumford, as the percaffion of the balls. Therefore, the whole particles, instead of vibrating, will remain at reft, and the laft particle alone fly off. This must happen in every row of particles in the body;: confequently, the application of heat, inftead of expanding the dimen fions of the body, will only caufe its anterior surface to split and fly off in fplinters, in a direction determined by the mode of ap plying the heat. If the heat is radiated from one fide only, the oppofite furface will fly off. If it is radiated from two contiguous fides, the extreme parts will fly off diagonally. If it is radiated from the centre, both furfaces will fplinter; and if it is equally radiated from oppofite fides, the whole body will be fhaken, but no other change whatever will be produced. So confonant to fact is this theory of vibration and incessant motion !

We here take leave of Count Rumford's fpeculations upon the nature of heat. After the ample difcuffion we have bestowed upon them, it would be very unneceffary to recapitulate the manifold objections to which they are obviously liable. We fhall, therefore, only exprefs an earnest with that this ingenious and perfeveting obferver would leave the amufement of framing hypothefes to inferior men, who cannot fubftantially affift the progress of inductive philofophy, and whofe errors or fancies can have no detrimental