[Footnote: A. de Rochas in the Revue Scientifique.]
In the following notes I shall recall a few experiments that indicate under what conditions the human organism is permitted to remain unharmed amid flames. These experiments were published in England in 1882, in the twelfth letter from Brewster to Walter Scott on natural magic. They are, I believe, not much known in France, and possess a practical interest for those who are engaged in the art of combating fires.
At the end of the last century Humphry Davy observed that, on placing a very fine wire gauze over a flame, the latter was cooled to such a point that it could not traverse the meshes. This phenomenon, which he attributed to the conductivity and radiating power of the metal, he soon utilized in the construction of a lamp for miners.
Some years afterward Chevalier Aldini, of Milan, conceived the idea of making a new application of Davy's discovery in the manufacture of an envelope that should permit a man to enter into the midst of flames. This envelope, which was made of metallic gauze with 1-25th of an inch meshes, was composed of five pieces, as follows: (1) a helmet, with mask, large enough, to allow a certain space between it and the internal bonnet of which I shall speak; (2) a cuirass with armlets; (3) a skirt for the lower part of the belly and the thighs; (4) a pair of boots formed of a double wire gauze; and (5) a shield five feet long by one and a half wide, formed of metallic gauze stretched over a light iron frame. Beneath this armor the experimenter was clad in breeches and a close coat of coarse cloth that had previously been soaked in a solution of alum. The head, hands, and feet were covered by envelopes of asbestos cloth whose fibers were about a half millimeter in diameter. The bonnet contained apertures for the eyes, nose, and ears, and consisted of a single thickness of fabric, as did the stockings, but the gloves were of double thickness, so that the wearer could seize burning objects with the hands.
Aldini, convinced of the services that his apparatus might render to humanity, traveled over Europe and gave gratuitous representations with it. The exercises generally took place in the following order: Aldini began by first wrapping his finger in asbestos and then with a double layer of wire gauze. He then held it for some instants in the flame of a candle or alcohol lamp. One of his assistants afterward put on the asbestos glove of which I have spoken, and, protecting the palm of his hand with another piece of asbestos cloth, seized a piece of red-hot iron from a furnace and slowly carried it to a distance of forty or fifty meters, lighted some straw with it, and then carried it back to the furnace. On other occasions, the experimenters, holding firebrands in their hands, walked for five minutes over a large grating under which fagots were burning.
In order to show how the head, eyes, and lungs were protected by the wire gauze apparatus, one of the experimenters put on the asbestos bonnet, helmet, and cuirass, and fixed the shield in front of his breast. Then, in a chafing dish placed on a level with his shoulder, a great fire of shavings was lighted, and care was taken to keep it up. Into the midst of these flames the experimenter then plunged his head and remained thus five or six minutes with his face turned toward them. In an exhibition given at Paris before a committee from the Academic des Sciences, there were set up two parallel fences formed of straw, connected by iron wire to light wicker work, and arranged so as to leave between them a passage 3 feet wide by 30 long. The heat was so intense, when the fences were set on fire, that no one could approach nearer than 20 or 25 feet; and the flames seemed to fill the whole space between them, and rose to a height of 9 or 10 feet. Six men clad in the Aldini suit went in, one behind the other, between the blazing fences, and walked slowly backward and forward in the narrow passage, while the fire was being fed with fresh combustibles from the exterior.
One of these men carried on his back, in an ozier basket covered with wire gauze, a child eight years of age, who had on no other clothing than an asbestos bonnet. This same man, having the child with him, entered on another occasion a clear fire whose flames reached a height of 18 feet, and whose intensity was such that it could not be looked at. He remained therein so long that the spectators began to fear that he had succumbed; but he finally came out safe and sound.
One of the conclusions to be drawn from the facts just stated is that man can breathe in the midst of flames. This marvelous property cannot be attributed exclusively to the cooling of the air by its passage through the gauze before reaching the lungs; it shows also a very great resistance of our organs to the action of heat. The following, moreover, are direct proofs of such resistance. In England, in their first experiment, Messrs. Joseph Banks, Charles Blagden, and Dr. Solander remained for ten minutes in a hot-house whose temperature was 211° Fahr., and their bodies preserved therein very nearly the usual heat. On breathing against a thermometer they caused the mercury to fall several degrees. Each expiration, especially when it was somewhat strong, produced in their nostrils an agreeable impression of coolness, and the same impression was also produced on their fingers when breathed upon. When they touched themselves their skin seemed to be as cold as that of a corpse; but contact with their watch chains caused them to experience a sensation like that of a burn.
A thermometer placed under the tongue of one of the experimenters marked 98° Fahr., which is the normal temperature of the human species.
Emboldened by these first results, Blagden entered a hot-house in which the thermometer in certain parts reached 262° Fahr. He remained therein eight minutes, walked about in all directions, and stopped in the coolest part, which was at 240° Fahr. During all this time he experienced no painful sensations; but, at the end of seven minutes, he felt an oppression of the lungs that inquieted him and caused him to leave the place. His pulse at that moment showed 144 beats to the minute, that is to say, double what it usually did. To ascertain whether there was any error in the indications of the thermometer, and to find out what effect would take place on inert substances exposed to the hot air that he had breathed, Blogden placed some eggs in a zinc plate in the hot-house, alongside the thermometer, and found that in twenty minutes they were baked hard.
A case is reported where workmen entered a furnace for drying moulds, in England, the temperature of which was 177°, and whose iron sole plate was so hot that it carbonized their wooden shoes. In the immediate vicinity of this furnace the temperature rose to 160°. Persons not of the trade who approached anywhere near the furnace experienced pain in the eyes, nose, and ears.
A baker is cited in Angoumois, France, who spent ten minutes in a furnace at 132° C.
The resistance of the human organism to so high temperatures can be attributed to several causes. First, it has been found that the quantity of carbonic acid exhaled by the lungs, and consequently the chemical phenomena of internal combustion that are a source of animal heat, diminish in measure as the external temperature rises. Hence, a conflict which has for result the retardation of the moment at which a living being will tend, without obstacle, to take the temperature of the surrounding medium. On another hand, it has been observed that man resists heat so much the less in proportion as the air is saturated with vapors. Dr. Berger, who supported for seven minutes a temperature varying from 109° to 110° C. in dry air, could remain only twelve minutes in a bagnio whose temperature rose from 41° to 51.75°. At the Hammam of Paris the highest temperature obtained is 87°, and Dr. E. Martin has not been able to remain therein more than five minutes. This physician reports that in 1743, the thermometer having exceeded 40° at Pekin, 14,000 persons perished. These facts are explained by the cooling that the evaporation of perspiration produces on the surface of the body.
Edwards has calculated that such evaporation is ten times greater in dry air in motion than in calm and humid air. The observations become still more striking when the skin is put in contact with a liquid or a solid which suppresses perspiration. Lemoine endured a bath of Bareges water of 37° for half an hour; but at 45° he could not remain in it more than seven minutes, and the perspiration began to flow at the end of six minutes. According to Brewster, persons who experience no malaise near a fire which communicates a temperature of 100° C. to them, can hardly bear contact with alcohol and oil at 55° and mercury at 48°.
The facts adduced permit us to understand how it was possible to bear one of the proofs to which it is said those were submitted who wished to be initiated into the Egyptian mysteries. In a vast vaulted chamber nearly a hundred feet long, there were erected two fences formed of posts, around which were wound branches of Arabian balm, Egyptian thorn, and tamarind--all very flexible and inflammable woods. When this was set on fire the flames arose as far as the vault, licked it, and gave the chamber the appearance of a hot furnace, the smoke escaping through pipes made for the purpose. Then the door was suddenly opened before the neophyte, and he was ordered to traverse this burning place, whose floor was composed of an incandescent grating.
The Abbé Terrason recounts all these details in his historic romance "Sethos," printed at the end of last century. Unfortunately literary frauds were in fashion then, and the book, published as a translation of an old Greek manuscript, gives no indication of sources. I have sought in special works for the data which the abbé must have had as a basis, but I have not been able to find them. I suppose, however, that this description, which is so precise, is not merely a work of the imagination. The author goes so far as to give the dimensions of the grating (30 feet by 8), and, greatly embarrassed to explain how his hero was enabled to traverse it without being burned, is obliged to suppose it to have been formed of very thick bars, between which Sethos had care to place his feet. But this explanation is inadmissible. He who had the courage to rush, head bowed, into the midst of the flames, certainly would not have amused himself by choosing the place to put his feet. Braving the fire that surrounded his entire body, he must have had no other thought than that of reaching the end of his dangerous voyage as soon as possible. We cannot see very well, moreover, how this immense grate, lying on the ground, was raised to a red heat and kept at such a temperature.
It is infinitely more simple to suppose that between the two fences there was a ditch sufficiently deep in which a fire had also been lighted, and which was covered by a grating as in the Aldini experiments. It is even probable that this grating was of copper, which, illuminated by the fireplace, must have presented a terrifying brilliancy, while in reality it served only to prevent the flames from the fireplace reaching him who dared to brave them.