| Fune 15, 1871] 
NATURE 
127 


tion may raise the platinum to bright redness, so as to 
cause the remainder of the mixture to explode. The 
promptness of this action is greatly augmented by re- 
ducing 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 in- 
stantly. In virtue of its extreme porosity, a similar power 
is possessed by charcoal. Itis not strong enough to cause 
the oxygen and hydrogen to combine like the spongy 
platinum, but it so squeezes the more condensible vapours 
together, and also acts with such condensing power upon 
the oxygen of the air, as to bring both within the com- 
bining distance, thus enabling the oxygen to attack and 
destroy the vapours in the pores of the charcoal. In this 
way, effluvia of all kinds may be virtually burnt up, and 
this is the principle of the excellent charcoal respirators 
invented by Dr. Stenhouse. Armed with one of these, 
you may go into the foulest-smelling places without having 
your nose offended. Some of you will remember Dr. Sten- 
house lecturing in this room with a suspicious-looking 
vessel in front of the table. That vessel contained a de- 
composing cat. It was covered with a layer of charcoal, 
and nobody knew until told of it what the vessel con- 
tained. 
Imay be permitted in passing to give my testimony as 





























































































to the efficacy of these charcoal respirators in providing 
warm air for the lungs. Not only is the sensible heat of 
the breath in part absorbed by the charcoal, but the con- 
siderable amount of latent heat which accompanies the 
aqueous vapour from the lungs is rendered free by the 
condensation of the vapour in the pores of the charcoal. 
Each particle of charcoal is thus converted into an in- 
cipient ember, and warms the air as it passes inwards. 
But while powerful to arrest vapours, the charcoal 
respirator is ineffectual as regards smoke. The particles 
get freely through the respirator. In a series of them 
tested downstairs, from half a minute to a minute was the 
limit of endurance. This might be exceeded by Faraday’s 
method of emptying the lungs completely, and then filling 
them before going into a smoky atmosphere. In fact, 
each solid smoke particle is itself a bit of charcoal, and 
carries on it, and in it, its little load of irritating vapours. 
It is this, far more than the particles of carbon themselves, 
that produces the irritation. Hencetwo causes of offence 
are to be removed : the carbon particles which convey the 
irritant by adhesion and condensation, and the free vapour 
which accompanies the particles. The moistened cotton- 
wool I knew would arrest the first, fragments of char- 
coal I hoped would stopthesecond. Inthe first fireman’s 
respirator, Mr. Carrick’s arrangement of two valves, the 
one for inhalation, the other for exhalation, are preserved. 
But-the portion of it which holds the filtering and absor- 


bent substances is prolonged to a depth of four or five 
inches (see Fig. 1). On the partition of wire gauze gr at the 
bottom of the space which fronts the mouth, is placed a 
layer of cotton-wool, c, moistened with glycerine ; then a 
thin layer of dry wool, c’ ; then a layer of charcoal frag- 
ments ; asecond thin layer of dry cotton wool, succeeded 
by a layer of fragments of caustic lime. The succession of 
the layers may be changed without injury to the action. 
A wire-gauze cover, shown in plan below Fig. 2, keeps the 
substances from falling out of the respirator. In the 
densest smoke that we have hitherto employed, the layer 
of lime has not been found necessary, nor is it shown in 
the figure ; in a flaming building, indeed, the mixture ot 







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OF BOTTOM COVER 
PLAN 
FIG. 2, 
air with the smoke never permits the carbonic acid to 
become so dense as to be irrespirable. But in a place 
where the gas is present in undue quantity, the fragments 
of lime would materially mitigate its action. 
In a small cellar-like chamber downstairs, with a stone 
flooring and stone walls, the first experiments were made. 
We placed there furnaces containing resinous pine-wood, 
lighted the wood, and placing over it a lid which prevented 
too brisk a circulation of the air, generated dense volumes 
of smoke. With our eyes protected by suitable glasses, 
my assistant and I have remained in this room for half an 
hour and more, when the smok2 was so dense and pun- 
gent that a single inhalation through the undefended 
