[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.
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