on the combustion of gaseous mixtures. 
83 
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 pro- 
trudes on the exterior of the lamp, for this would fire ex- 
ternally 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 
apparatus to be tried in the coal mines of Newcastle and 
Whitehaven : and I anxiously wait for the accounts of their 
effects in atmospheres in which no other permanent light 
can be produced by combustion. 
Lo?idon, Jan . 22, 1817. 
Explanation of Plate V. representing different forms of the 
Miners’ Safe-lamp , with the apparatus for giving light in 
explosive mixtures. 
a. Represents the single cylinder of wire-gauze ; the fold- 
ings cc. a. ot. must be very well doubled and fastened by wire. 
If the cylinder be of twilled wire-gauze, the wire should be 
at least of the thickness of — of an inch, and of iron or 
copper, and 30 in the warp and 16 or 18 in the weft. 
M 2 
