ep is possible.
Admiring, as I do, the bravery of our firemen, and hearing that smoke
was a more serious enemy than flame itself, I thought of devising a
fireman's respirator.

Our fire-escapes are each in charge of a single man, and it would be
of obvious importance to place it in the power of each of those men to
penetrate through the densest smoke, into the recesses of a house, and
there to rescue those who would otherwise be suffocated or burnt.
Cotton-wool, which so effectually arrested dust, was first tried; but,
though found soothing in certain gentle kinds of smoke, it was no
match for the pungent fumes of a resinous fire. For the purpose of
catching the atmospheric germs, M. Pouchet spread a film of glycerine
on a plate of glass, urged air against the film, and examined the dust
which stuck to it. The moistening of the cotton-wool with glycerine
was a decided improvement; still the respirator only enabled us to
remain in dense smoke for three or four minutes, after which the
irritation became unendurable. Reflection suggested that, besides the
smoke, there must be numerous hydrocarbons produced, which, being in a
state of vapour, would be very imperfectly arrested by the
cotton-wool. These, in all probability, were the cause of the
residual irritation; and if these could be removed, a practically
perfect respirator might possibly be obtained.

I state the reasoning exactly as it occurred to my mind. Its result
will be anticipated by many present. All bodies possess the power of
condensing, in a greater or less degree, gases and vapours upon their
surfaces, and when the condensing body is very porous, or in a fine
state of division, the force of condensation may produce very
remarkable effects. Thus, a clean piece of platinum-foil placed in a
mixture of oxygen and hydrogen so squeezes the gases together as to
cause them to combine; and if the experiment be made with care, the
heat of combination may raise the platinum to bright redness. The
promptness of this action is greatly augmented by reducing the
platinum to a state of fine division. A pellet of 'spongy platinum,'
for instance, plunged into a mixture of oxygen and hydrogen, causes
the gases to explode instantly. In virtue of its extreme porosity, a
similar power is possessed by charcoal. It is not strong enough to
cause the oxygen and hydrogen to combine like the spongy platinum, but
it so squeezes the more condensable vapours, and acts with s