26 On the Combustion of Gaseous Mixtures. 
been entirely destroyed by an atmosphere of pure coal gas; and by 
increasing its thickness the period might be made still longer, 
The phenomenon of the ignition of the platinum takes place 
feebly in a mixture consisting of two of air and one of coal gas, and 
brilliantly in a mixture consisting of three of air and one of coal 
gas: the greater the quantity of heat produced the greater may 
be the quantity of the coal gas, so that a large tissue of wire will 
burn in a more inflammable mixture than single filaments, and a 
wire made white hot will burn in a more inflammable mixture 
than one made red hot. Ifa mixture of three parts of air and 
one of fire-damp be introduced into a bottle, and inflamed at its 
point of contact with the atmosphere, it will not explode, but 
will burn like a pure inflammable substance. If a fine wire of 
platinum coiled at its end be slowly passed through the flame, 
it will continue ignited in the body of the mixture, and the same 
gaseous matter will be found to be inflammable and to support 
combustion. 
. There is every reason to hope that the same phenomena will 
occur with the cage of platinum in the fire-damp, as those which 
have been described in its operation on mixtures of coal gas. In 
trying experiments in fire-damp, the greatest care must be taken 
that no filament or wire of platinum protrudes on the exterior 
of the lamp, for this would fire externally an explosive mixture. 
However small the mass of platinum which kindles an explosive 
mixture in the safe-lamp, the result is the same as when large 
masses are used; the force of the explosion is directed to, and 
the flame arrested by, the whole of the perforated tissue. 
When a large cage of wire of platinum is introduced into a 
very small safe-lamp, even explosive mixtures of fire-damp are 
burnt without flame; and by placing any cage of platinum in 
the bottom of the lamp round the wick, the wire is prevented 
from being smoked. I have sent lamps furnished with this ap- 
paratus to be tried in the coal mines of Newcastle and White- 
haven: and I anxiously wait for the accounts of their effects in 
atmospheres in which no other permanent light can be produced 
by combustion. 
London, Jan. 22, 1817. 
Explanation of Figures, Plate I. 
Fig. A is a small cage made of wire of platinum, of 1-70th or 
1-80th of an inch in thickness, fastened to a wire for raising it 
above the wick, for giving light in inflammable media, containing 
too little air to be explosive. 
Figures B and B are a similar cage for placing in the bottom 
of the lamp, to prevent it from being smoked by the per a 
. On 
