Philofophical Tranfactions. Vol. LXV. Part II. for the Year 1775. Continued from p. 271, and concluded. We presume to have given fufficient hints in our last article on this fubject, to put it beyond a doubt, that the air, or atmofphere, is not fufficiently, denfe and heavy to poffefs the degree of heat, which it nevertheless is capable of communicating from one folid to another. The obfervation of Dr. Blagdon, therefore, in the first part of the volume, is inaccurately expreffed. Speaking of the bodies in the heated room, he says, "All the "pieces of metal there, even our watch-chains, felt fo hot, that "we could scarcely bear to touch them for a moment: whiift the "air, from which the metal had derived all its heat, was only un"pleasant." Again he calls this degree of heat poteffed by the metals, the real heat of the air; confeffing, at the fame time, that the air communicated its heat fo flowly, that the thermometers brought with him into the room, did not in twenty minutes acquire that heat by feveral degrees. Yet furely, if fuch heat was the real heat of the air, they might be reasonably expected to have acquired it fooner. But the truth is, as before obferved, the degree of heat was that only of the furrounding folids of equal tenacity and denfity; the air being only the me dium of communication. Indeed all the experiments recorded in the Philosophical Transactions on this fubject, appear to confirm it. Dr. Dobson obferves, Art. XLV. that "fuch bodies as are weak conductors of fire from air, may be placed in air, "without receiving the heat of this medium."If, instead of faying conductors of fire, he had faid retainers of heat, or conductors of fire from ignited or heated folids, he would have been nearer the truth; and the experiments he enumerates would have been more plaufibly accounted for. "There would then be little wonder why the albumen ovi remains fluid in air heated to 224°. Hence likewife the frog, the lizard, the camelion, &c. retain their natural temperature, and feel cold to the touch, though perpetually furrounded with air hotter than their own bodies. Hence alfo, the human body keeps nearly its own tempera ture, in a flove heated to 224°: or may even pafs without injury into air heated to a much greater degree, according to the obfervations of Du Hamel and Tillett, publifhed in the Memoirs of the Academy of Sciences*. Hence, on the other hand, the bees wax melted from the mere contact of the air in experiment VIII; and in experiment v 1, the albumen ovi was coagulated on the intervention of another body, which is a ftrong conductor of fire or retainer of heat." That the experiments of the Drs. Fordyce and Blagdon, refpecting the poflibility of an animal's fupporting life in air, Memoires pour 1761, which which would communicate to and from metallic bodies a much greater degree of heat than it ever could do to the bodies of li ving animals, they are undoubtedly conclufive fo far as they ferve to explode the experiments of Boerhaave. They may alfo ferve to explode, in fome degree, the opinion of thofe, who conceive the heat of the animal body merely owing to the friction of the blood against the sides of the blood-veffels, in circulation: because in fuch cafe, it were reasonable to expect, that in proportion to the acceleration of the pulfe, fuch heat would be increased; which is not found to be the cafe.* We do not conceive, however, that these experiments tend to what is confeffedly their principal ufe; viz. to explode the long approved doctrine that all heat is the effect of attrition or fermentation. For, though it may be true, as Dr. Blagdon ob ferves, that no theory which the mechanical or chemical phyfi cians have as yet devifed, is fufficient to explain the powers of producing or deftroying heat in all cafes and circumstances, this is no good reason why fuch theory, which will hold good in fo many cafes, fhould be rejected till we are furnished with a better. For we can by no means admit of his unphilosophical expedient of recurring to occult caufes, by telling us it is "a power of fuch a nature, that it can only be referred to the "principle of life, and probably exercised only in those parts of "our bodies in which life feems peculiarly to refide." We would almost as foon adopt the term in morals, and, after the rakehelly cant of profligates, call debauchery feeing life, as adopt it in phyfics, as an immechanical principle of generating heat or cold, as the fituation of the animal might require it. The ingenious Mr. John Hunter has, it feems, carried his inveftigation of this principle into the vegetable world; pretending that vegetables as well as animals, while alive, have the power of producing or generating heat. Had he faid of generating cold too in certain circumítances, he would have been equally in the right for, as he justly obferves," it is in both only a power "of oppofition and refiftance, it is not found to exert itself fpontaneoufly and unprovoked; but must always be excited "by the energy of fome external frigorific agent." But where is the wonder of all this? Does not every body, or fyftematic combination of bodies tend to the prefervation of its present ftate, whether of reft or motion, heat or cold, unlefs affected by some external agent? What should make it do otherwise ? This power of generating heat [or rather, according to him, of refifting cold] in animals, docs not depend on the motion of the blood, as Unless, indeed, we adopt the new doctrine laid down in the late Dr. Goldsmith's Survey of Experimental Philofophy; in which we are told, that friction is not increased by celerity of motion. Rev. a fome have fuppofed, because it belongs to animals who have no circulation; befides the nose of a dog, which is nearly always of the fame heat in all temperatures of the air, is well fupplied with blood nor can it be faid to depend upon the nervous fyftem, for it is found in animals that have neither brain nor nerves. It is then molt probable, that it depends on fome other principle peculiar to both, and which is one of the properties of life; which can, and does, act independently of circulation, fenfation, and volition; viz. that power which preferves and regulates the internal machine, and which appears to be common to animals and vegetables, This principle is in the most perfect state when the body is in health, and in many deviations from that state, we find that its action is extremely uncertain and irregular; fometimes rifing higher than the standard, and at other times falling much below it." All this, however, is faying but little. The principle of life is in its most perfect ftate when the animal or vegetable is in health.-Doubtlefs; for when it is beft in health it is most perfectly alive. Again, when he tells us of a dormouse and a toad, which he endeavoured to freeze to death, he fays, "while the vigour of "life lafted, they defied the approach of the cold"-" their "motions became lefs violent by the finking of the vital pow"ers." Of the dormouse, that it died and became ftiff.". Of the toad, that "it did not die, and therefore was not frozen." But would it not be equally proper to fay, it was not frozen, " and therefore did not die ?"-There can be little doubt, had the cold been fufficiently increased, that either the animal would have been frozen and died, or would have died and been frozen the difference is merely verbal. What Mr. Hunter advances on the fame fubject, refpecting imperfect animals and vegetables, amounts to the fame thing, and is eafily accounted for. The life, both of animals and vegetables, confifts in a fyftem of motion, which, while it is preferved, poffeffes the property of heat or cold of a certain temperature, peculiar to their kind. It is natural, it is mechanical, for fuch a fyftem to refift or oppose every external agent, tending to difturb or diverfify its mode of existence; whether by increafing or diminishing the velocity of its motion, i. e. tending to make it either hotter or colder. And though this property may not be juftly attributed either to circulation, fenfation, or volition, it may be juftly imputed to them all, or to fomething fimilar; to which, if thefe philofophers are determined to give the name of Life, they may; but there appears to us no new discovery in the thing, whatever novelty there may be in the expreffion. VOL. III. Z z K. Garrick's 1 Garrick's Looking Glafs: Or, The Art of rifing on the Stage. A We justly praise, or justly blame. SWIFT. By his adopting of this motto, our author of the five stars appears to think the knowledge of his name would be no recommendation to his poem. Or, perhaps, he might have other reasons for concealing it; especially if he be in any fhape connected with the stage. Be this as it may, he certainly discovers an ease and facility in verfification, that speak him no novice. And yet he is as evidently a very young writer, or a very careless one; his thoughts and numbers running as loosely as if he had penned the whole fifteen hundred lines ftans pede in uno. Not but that there is difplayed fome poetical invention, in what may be called the machinery of the piece; the writer having employed Hermes, the mufes, the graces, together with the ghosts of departed poets, as well as of the dramatic characters they drew in the bu finefs of the compofition. Of the didactic merit of this production, our readers may form fome idea from the following extract from Garrick's inftructions to his pupils, the players.--After recommending to them a "well-fized Looking-Glafs," and expatiating on its general ufe, he proceeds, "The glass may teach to bow and kneel, The want of fenfibility. But then, 'twill take up all your leifure, There's many a wheel, and many a catch, Your lookers-on can ne'er divine, Enough Enough for them, if truth it tell, And who's to find the fecret out: Take heed, 'twill seem all skill and knowledge, Might pose the fellow of a college. Have you not feen, in LɛAR, and Foot, If well the changeling throws his hat, The eye-brow should be broad and dark, Give him the dark affaffin's airs, Much, much, dear folks, depends on drefs: The flourish, when she gives the blow, The thundering boaft of bluftering PIERRE, |