on the Combustion of Gaseous Mixtures. 25 
eulation of air, answer as well as fine wires; and a large surface 
of platinum may be made red hot in the vapour of ether, or in 
a combustible mixture of coal gas and air. 
I need not dwell upon the connection of these facts respecting 
slow combustion, with the other facts I have described in the 
history of flame. Many theoretical views will arise from this 
connection, and hints for new researches, which I hope to be 
able to pursue in another communication. I shall now con- 
clude by a practical application. By hanging some coils of fine 
wire of platinum, or a fine sheet of platinum or 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 quantity of fire-damp, the glow of the 
metal will continue to guide him; and by placing the lamp in 
different parts of the gallery, 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 continues ignited, for even this phenomenon ceases when 
the foul air forms about 2-5ths 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 1-70th of an inch in thickness, 
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 continued to increase till the flame 
of the wick was extinguished, 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 mo- 
ment of the extinction the cage of platinum became white hot, 
and presented a most brilliant light. By increasing the quantity 
of the coal gas still further, the ignition of the platinum beeame 
less vivid. When its light was barely sensible, small quantities 
of air were admitted, its heat speedily increased ; and by regu- 
lating the admission of coal gas and air it again became white 
hot, and soon after lighted the flame in the cylinder, which as 
usual, by the addition of more atmospherical air, re-kindled the 
flame of the wick. 
_ This experiment has been very often repeated, and always with 
the same results. When the wire for the support of the cage, 
whether of platinum, silver, or copper, was very thick, it re- 
tained sufficient heat to enable the fine platinum wire to re- 
kindle in a proper mixture a half a minute after its light had 
been 
