An Account of fome curious Experiments tried lately in London and Liverpool, with very great Degrees of Heat and Cold upon animal and vegetable Bodies, and of Cold upon vegetable Bodies, proving that fuch Bodies, while aliwe, are endued with many uncommon Powers, particularly thofe of bearing Heat and Cold, and even generating the one, occafionally, in oppofition to the other. From the Philofophical Transactions.

ARTICLE the FIRST. Experiments in an beated Room. By Matthew Dobson, M. D. In a Letter to John Fothergill, M. D.

I

F. R. S.

Liverpool, April 25, 1775. DEAR SIR, PERUSED with particular pleasure your short account of the curious experiment made by Mr. Banks and Dr. Solander. The fame, and fome additional experiments, have been made here; the refult of which I should fooner have tranfmitted to you, had I not been prevented by the constant engagements of my profeffion.

Experiments.

I. The fweating room of our Public Hofpital at Liverpool, which is nearly a cube of nine feet, lighted from the top, was heated till the quick filver flood at 224° on Fahrenheit's fcale, nor would the tube of the thermometer indeed admit the heat to be raised higher. The thermometer was fufpended by a fring fixed to the wooden frame of the fky-light,

and hung down about the centre of the room. Myfelf and several others were at this time inclosed in the ftove, without experiencing any oppreffive or painful fenfation of heat, proportioned to the degree pointed out by the thermometer. Every metalic about us foon became very hot.

II. My friend Mr. Park, an ingenious furgeon of this place,

went into the ftove heated to 202°. After ten minutes I found the pulfe quickened to 120. And to determine the increase of the animal heat, another thermometer was handed to him, in which the quickfilver already ftood at 98°; but it rofe only to 99%, whether the bulb of the thermometer was inclofed in the palms of the hands, or received into the mouth *. The natural ftate of this gentleman's pulfe is about 65.

III. Another gentleman went through the fame experiment in the fame circumstances, and with the fame effects.

IV. One of the porters to the Hofpital, a healthy young man, and the pulfe 75, was inclosed in the ftove when the quickfilver ftood at 210°; and he remained there, with little inconvenience, for 20 minutes. The pulfe, now 164, and the animal heat, determined by another thermometer as in the former experiments, was

1011.

V. A young gentleman of a delicate. and irritable habit, whose natural pulfe is about 80, remained in the fove ten minutes when heated to 224°. The pulse rofe

to

to 145, and the animal heat to 102°. This gentleman, who had been frequently in the ftove during the courfe of the day, found himfelf feeble, and difpofed to break out into fweats for 24 hours after the experiment.

VI. Two fmall tin veffels, containing each the white of an egg, were put into the flove heated to 224°. One of them was placed on a wooden feat near the wall, - and the other fufpended by a ftring about the middle of the ftove. Atter ten minutes, they began to coagulate; but the coagulation was fenfibly quicker and firmer in that which was fufpended, than in that which was placed on the wooden feat. The progrefs of the coagulation was as follows: it was first formed on the fides, and gradually extended itself; the whole of the bottom was next coagulated; and last of all the middle part of the top.

VII. Part of the fhell of an egg was peeled away, leaving only the film which furrounds the white; and part of the white being drawn out, the film funk fo as to form a little cup. This cup was filled with fome of the albumen ovi, which was confequently detached as much as poffible from every thing but the contact of the air and of the film which formed the cup. The lower part of the egg ftood upon fome light tow in a common gallipot, and was placed on the wooden feat in the ftove. The quick filver in the thermometer ftill continued at 224°. After remaining in the ftove for an hour, the lower part of the egg, which was covered with the fhell, was firmly coagulated; but that which was in the little cup was fluid and tranfparent. At

the end of another hour it was Aill fluid, except on the edges where it was thinneft; and here it was ftill tranfparent; a fufficient proof that it was dried, not coagulated.

VIII. A piece of bees wax, placed in the fame fituation with the albumen ovi of the preceding experiment, and expofed to the fame degree of heat in the ftove, began to melt in five minutes: another piece fufpended by a ftring, and a third piece put into the tin vessel and fufpended, began likewise to liquify in five minutes.

Obfervations

That heated air fhould have fuch a fpeedy and powerful effect in quickening the pulfe, while the animal heat is little altered from its natural ftandard; that the human body fhould fo eafily bear to be furrounded with air heated to 224°; that the albumen ovi, which begins to coagulate in water at 150°, fhould remain fluid in 224°; and that the fame albumen ovi, fill placed in air heated to 224, fhould coagulate, if in contact either with tin or its own shell, are facts as fingular as they are difficult of explanation. From the different effects of heated air on the pulfe and the heat of the body, do we not difcover the fallacy of that theory of animal heat which has been adopted by Boerhaave and other celebrated phyfiologists? They fuppofe that animal heat is produced by the attrition of the globules of the circulating fluids against the fides of the containing veffels; but in feveral of the preceding experiments, the circulation was amazingly quickened, with little increase of the animal heat. But whence is it that the human body G 3

can

can bear, without immediate in jury, to be furrounded with air heated to 224° And whence is it, that the albumen ovi does not coagulate in this degree of heat? Is it that fire as it paffes into fome bodies becomes latent, agreeable to a doctrine which has for fome time been taught at Edinburgh by Profeffor BLACK? Or does fire become fixed and quiefcent, according to a fimilar fyftem adopted by Dr. Franklin? Air we know exifts either in a fixed or elaftic flate; and fire may in like manner exift in bodies, either in a latent, fixed, and quiefcent; or in a fenfible, fluid, and active ftate. Agreeable to this idea, the bees wax receives the fire in an active ftate, and diffolves; while the human body and the albumen ovi, receiving the fire in a latent ftate, are little altered in their temperature. Let each of thefe, however, be put in contact with a different body, tin for inftance; and though the heat of the air continues the fame, yet the fire no longer enters in a latent ftate, but with all its fenfible and active powers; for the albumen ovi fufpended in a tin veffel foon coagulates; and the human body, covered with the fame metal, would quickly experience an intolerable and deftructive degree of heat. Or are the above phænomena more fatisfactorily explained, by confidering different bodies as poffeffing different conducting powers; fome being rong, others weak conductors of fire? All thofe bodies then which are weak conductors of fire from air, may be placed in air, without receiving the

heat of this medium. Hence the albumen ovi remains fluid in sir 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 temperature, in a ftove 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, published in the Memoirs of the Academy of Sciences +. On the other hand, all thofe bodies which are powerful conductors of fire from air, are influenced in proportion when furrounded with this medium. The bees wax melted from the mere contact of the air in experiment VIII; and in experiment VI. the albumen ovi was coagulated on the intervention of another body, which is a ftrong conductor of fire from air. But whether this method of reafoning on the natural caufe of thefe effects be just or not, the final cause is obvious, and is to be refolved into the wife and benevolent appointment of the Almighty. Man is happily fo framed, as to poffefs a power of keeping nearly the fame tenor of heat, in all the variations of the temperature of the air in fummer and winter, in hot and cold climates; and confequently changes his fituation on the furface of the globe, with much lefs inconvenience or injury, than he could otherwise have done. The fame power likewife happily adapts different animals to their

Part, p. 91.

respective

respective destinations. The lizard and the camelion remain cool under the equator, while the whale and porpoife retain a degree of heat above that of the human body, though furrounded with the waters of the coldest Northern feas, and amidft mountains of ice in the neighbourhood of the Pole.

Should you think thefe experiments and obfervations on heated air of fufficient importance to be communicated to the Royal Society, they are at your difpofal.

I have the pleafure to find, that Dr. Priestley is profecuting his very ingenious inquiries on air. In a letter I lately received from him he informs me, that he has difcovered a fpecies of air, which will preserve animal life fix times longer than atmospheric air.

I remain with great esteem, &c.

ARTICLE the SECOND.

for a very different purpofe; which was no other than to fatisfy myfelf, whether an animal could retain life after it was frozen, as had been confidently afferted both of fish and fnakes. I mention this, to account for what might otherwife be attributed to negligence. and inattention; namely, that lit tle nicety was ufed in measuring the precife degrees of the cold applied in thefe experiments. Accuracy in this particular was not aimed at, being of no confequence in the inquiry more immediately before me. The cold produced was firft by means of ice and fnow with fal ammeniac or fea falt, and was about 10° of Fahrenheit's thermometer. Then ice, fo cooled, was mixed with fpirit of nitre; but what degree of cold was thus produced I did not examine. This cold mixture was made in a tub furrounded with woollen cloths, and covered with the fame, to prevent the effects of the heat of the atmosphere upon the mixture itself, and to preferve, as much as poffible, a cold atmosphere within the veffel. The animal juices, the blood for example, freeze at 25°; fo that a piece of dead flesh could be frozen in fuch an atmosphere.

Experiments on Animals and Vegetables, with refpect to the Power of producing Heat. By John Hunter, F. R. S.

THE HE ingenious experiments and obfervations lately prefented to this learned Society, upon a power which animals feem to poffefs of generating cold, induced me to look over my notes of certain experiments and obfervations made in the year 1766, which indicate an oppofite power in animals; whereby they are capable of refiiling any external cold while alive, by generating within themfelves a degree of heat fufficient to counteract it. Thefe experiments were not originally inttituted in view of the difcovery, which in the event refulted from them, but