As to M. Chabert, the “Morning Chronicle” account says, “But now came the grand and terrific exhibition—the entering the oven—for which expectation was excited to the highest pitch. We had the curiosity to apply the unerring test of the thermometer to the inside of the oven, and found the maximum of heat to be 220 deg. M. Chabert, being dressed in a loose black linen robe, rendered, he assured us, as fireproof as asbestos, by a chemical solution, entered the oven amidst the applause of the spectators. He continued like a modern Shadrach in the fiery furnace, and after a suspense of about 12 minutes, again appeared to the anxious spectators, triumphantly bearing the beef-steak fully dressed, which he had taken into the oven with him raw. M. Chabert also exhibited to us the thermometer, which he had taken into the oven with him at 60 deg., and which was now up to 590 deg. We need not say that the bulb had been kept in the burning embers, of which it bore palpable signs. This was a mere trick, unworthy of the exhibition, for Mons. Chabert really bore the oven heated to 220 deg. for full twenty minutes. Whether we were emulous of Paul Pry, and peeped under the iron door of the oven, and beheld the beef-steak and leg of mutton cooking upon a heap of charcoal and embers concealed in the corner of the oven, we must not say, ‘it were too curious to consider matters after that manner.’ We are only doing justice to Monsieur Chabert in saying, that he is the best of all fire-eaters we have yet seen, and that his performance is truly wonderful, and highly worthy of the public patronage. A man so impervious to fire, may ‘make assurance doubly sure, and take a bond of fate.’”
Stay, stay! Not quite so fast. M. Chabert is a man of tricks, but his only real trick failed to deceive; this was placing the bulb of the thermometer in burning embers, to get the mercury up to 590, while, in fact, the heat he really bore in the oven was only 220; which, as he bore that heat for “full twenty minutes,” the writer quoted deems “really wonderful.” That it was not wonderful for such an exhibitor to endure such a heat, will appear from the following statements.
About the middle of January, 1774, Dr. Charles Blagden, F.R.S., received an invitation from Dr. George Fordyce, to observe the effects of air heated to a much higher degree than it was formerly thought any living creature could bear. Dr. Fordyce had himself proved the mistake of Dr. Boerhaave and most other authors, by supporting many times very high degrees of heat, in the course of a long train of important experiments. Dr. Cullen had long before suggested many arguments to show, that life itself had a power of generating heat, independent of any common chemical or mechanical means. Governor Ellis in the year 1758 had observed, that a man could live in air of a greater heat than that of his body; and that the body, in this situation, continues its own cold; and the abbé Chappe d’Auteroche had written that the Russians used their baths heated to 60 deg. of Reaumur’s thermometer, about 160 of Fahrenheit’s. With a view to add further evidence to these extraordinary facts, and to ascertain the real effects of such great degrees of heat on the human body, Dr. Fordyce tried various experiments in heated chambers without chimneys, and from whence the external air was excluded. One of these experiments is thus related.
Dr. Blagden’s Narrative.
The honourable captain Phipps, Mr. (afterwards sir Joseph) Banks, Dr. Solander, and myself, attended Dr. Fordyce to the heated chamber, which had served for many of his experiments with dry air. We went in without taking off any of our clothes. It was an oblong square room, fourteen feet by twelve is length and width, and eleven in height, heated by a round stove, or cockle, of cast iron, which stood in the middle, with a tube for the smoke carried from it through one of the side walls. When we first entered the room, about two o’clock in the afternoon, the quicksilver in a thermometer, which had been suspended there stood above the 150th degree. By placing several thermometers in different parts of the room we afterwards found, that the heat was a little greater in some places than in others; but that the whole difference never exceeded 20 deg. We continued in the room above 20 minutes, in which time the heat had risen about 12 deg., chiefly during the first part of our stay. Within an hour afterwards we went into this room again, without seeing any material difference, though the heat was considerably increased. Upon entering the room a third time, between five and six o’clock after dinner, we observed the quicksilver in our only remaining thermometer at 198 deg.; this great heat had so warped the ivory frames of our other thermometers, that every one of them was broken. We now staid in the room, all together, about 10 minutes; but finding that the thermometer sunk very fast, it was agreed, that for the future only one person should go in at a time, and orders were given to raise the fire as much as possible. Soon afterwards Dr. Solander entered the room alone, and saw the thermometer at 210 deg., but, during three minutes that he staid there, it sunk to 196 deg. Another time, he found it almost five minutes before the heat was lessened from 210 deg., to 196 deg. Mr. Banks closed the whole, by going in when the thermometer stood above 211 deg.; he remained seven minutes, in which time the quicksilver had sunk to 198 deg.; but cold air had been let into the room by a person who went in and came out again during Mr. Banks’s stay. The air heated to these high degrees felt unpleasantly hot, but was very bearable. Our most uneasy feeling was a sense of scorching on the face and legs: our legs, particularly, suffered very much, by being exposed more fully than any other part to the body of the stove, heated red-hot by the fire within. Our respiration was not at all affected; it became neither quick nor laborious; the only difference was a want of that refreshing sensation which accompanies a full inspiration of cool air. Our time was so taken up with other observations, that we did not count our pulses by the watch: mine, to the best of my judgment by feeling it, beat at the rate of 100 pulsations in a minute, near the end of the first experiment; and Dr. Solander’s made 92 pulsations in a minute, soon after we had gone out of the heated room. Mr. Banks sweated profusely, but no one else: my shirt was only damp at the end of the experiment. But the most striking effects proceeded from our power of preserving our natural temperature. Being now in a situation in which our bodies bore a very different relation to the surrounding atmosphere from that to which we had been accustomed, every moment presented a new phenomenon. Whenever we breathed on a thermometer, the quicksilver sunk several degrees. Every expiration, particularly if made with any degree of violence, gave a very pleasant impression of coolness to our nostrils, scorched just before by the hot air rushing against them when we inspired. In the same manner our now cold breath agreeably cooled our fingers, whenever it reached them. Upon touching my side, it felt cold like a corpse; and yet the actual heat of my body, tried under my tongue, and by applying closely the thermometer to my skin, was 98 deg., about a degree higher than its ordinary temperature. When the heat of the air began to approach the highest degree which the apparatus was capable of producing, our bodies in the room prevented it from rising any higher; and, when it had been previously raised above that point, inevitably sunk it. Every experiment furnished proofs of this: towards the end of the first, the thermometer was stationary: in the second, it sunk a little during the short time we staid in the room: in the third, it sunk so fast as to oblige us to determine that only one person should go in at a time; and Mr. Banks and Dr. Solander each found, that his single body was sufficient to sink the quicksilver very fast, when the room was brought nearly to its maximum of heat.
These experiments, therefore, prove in the clearest manner, that the body has a power of destroying heat. To speak justly on this subject, we must call it a power of destroying a certain degree of heat communicated with certain quickness. Therefore, in estimating the heat which we are capable of resisting, it is necessary to take into consideration not only what degree of heat would be communicated to our bodies, if they possessed no resisting power, by the heated body, before the equilibrium of heat was effected; but also what time that heat would take in passing from the heated body into our bodies. In consequence of this compound limitation of our resisting power, we bear very different degrees of heat in different mediums. The same person who felt no inconvenience from air heated to 211 deg. could not bear quicksilver at 120 deg. and could just bear rectified spirit of wine at 130 deg. that is, quicksilver heated to 120 deg. furnished, in a given time, more heat for the living powers to destroy, than spirits heated to 130 deg. or air to 211 deg. And we had, in the heated room where our experiments were made, a striking, though familiar instance of the same. All the pieces of metal there, even our watch-chains, felt so hot that we could scarcely bear to touch them for a moment, whilst the air, from which the metal had derived all its heat, was only unpleasant. The slowness with which air communicates its heat was further shown, in a remarkable manner, by the thermometers we brought with us into the room; none of which, at the end of twenty minutes, in the first experiment, had acquired the real heat of the air by several degrees. It might be supposed, that by an action so very different from that to which we are accustomed, as destroying a large quantity of heat, instead of generating it, we must have been greatly disordered. And indeed we experienced some inconvenience; our hands shook very much, and we felt a considerable degree of languor and debility; I had also a noise and giddiness in my head. But it was only a small part of our bodies that excited the power of destroying heat with such a violent effort as seems necessary at first sight. Our clothes, contrived to guard us from cold, guarded us from the heat on the same principles. Underneath we were surrounded with an atmosphere of air, cooled on one side to 98 deg. by being in contact with our bodies, and on the other side heated very slowly, because woollen is such a bad conductor of heat. Accordingly I found, toward the end of the first experiment, that a thermometer put under my clothes, but not in contact with my skin, sunk down to 110 deg. On this principle it was that the animals, subjected by M. Tillet to the interesting experiments related in the “Memoirs of the Academy of Sciences” for the year 1764, bore the oven so much better when they were clothed, than when they were put in bare: the heat actually applied to the greatest part of their bodies was considerably less in the first case than in the last. As animals can destroy only a certain quantity of heat in a given time, so the time they can continue the full exertion of this destroying power seems to be also limited; which may be one reason why we can bear for a certain time, and much longer than can be necessary to fully heat the cuticle, a degree of heat which will at length prove intolerable. Probably both the power of destroying heat, and the time for which it can be exerted, may be increased, like most other faculties of the body, by frequent exercise. It might be partly on this principle, that, in M. Tillet’s experiments, the girls, who had been used to attend the oven, bore, for ten minutes, an heat which would raise Fahrenheit’s thermometer to 280 deg. In our experiments, however, not one of us thought he suffered the greatest degree of heat that he was able to support.[208]
We find then, that Dr. Fordyce, Dr. Blagden, Dr. Solander, the honourable captain Phipps, sir Joseph Banks, together, bore the heat at 198 deg.; that Dr. Solander went into the room at 210, sir Joseph Banks at 211; and that M. Tillet’s oven-girls bore a heat for ten minutes which would raise the thermometer to 280 deg., being 60 deg. higher than M. Chabert bore for ten minutes at White Conduit-house. Recent experiments in England fully corroborate the experiments referred to; and, in short, an extension of our knowledge in philosophical works will outjuggle jugglers of every description.