on the combustion of gaseous mixtures . 8 1 
hope to be able to pursue in another communication. I shall 
now conclude by a practical application. By hanging some 
coils of fine wire of platinum, or a fine sheet of platinum 
nr palladium above the wick of his lamp, in the wire-gauze 
cylinder, the coal miner, there is every reason to believe, will 
be supplied with light in mixtures of fire-damp no longer 
explosive ; and should his flame be extinguished by the quan- 
tity of fire-damp, the glow of the metal will continue to guide 
him, and by placing the lamp in different parts of the gal- 
lery, the relative brightness of the wire will show the state 
of the atmosphere in these parts. Nor can there be any 
danger with respect to respiration whenever the wire con- 
tinues ignited, for even this phenomenon ceases when the 
foul air forms about ^ of the volume of the atmosphere. 
I introduced into a wire-gauze safe-lamp a small cage 
made of fine wire of platinum of the of an inch in thick- 
ness, and fixed it by means of a thick wire of platinum about 
two inches above the wick which was lighted. I placed the 
whole apparatus in a large receiver, in which, by means of 
a gas holder, the air could be contaminated to any extent 
with coal gas. As soon as there was a slight admixture 
of coal gas, the platinum became ignited ; the ignition con- 
tinued to increase till the flame of the wick was extin- 
guished, and till the whole cylinder became filled with flame; 
it then diminished. When the quantity of coal gas was 
increased so as to extinguish the flame; at the moment of 
the extinction the cage of platinum became white hot, and 
presented a most brilliant light. By increasing the quan- 
tity of the coal gas still farther, the ignition of the platinum 
became less vivid. When its light was barely sensible, 
MDCCCXVII. M 
