Sir Humphry Davy. 241 
pits, with no other light than that derived from sparks of steel, or en- 
counter the hazard of a sudden and awful death. Their families 
were on the rack of tormenting fears, and parted with them, as they 
left their homes in the morning, with sad and gloomy forebodings.* 
In such a state of things, application was made to Sir Humphry 
Davy, whose rare union of scientific knowledge with mechanical in- 
genuity, marked him out as the man of all others most likely to af- 
ford relief. It seemed however a hopeless undertaking. It was 
like asking him to discover a method of making a coal of fire 
burn in the midst of a barrel of gun powder, without inflaming 
it. The process by which he advanced to the discovery was so cu- 
rious and instructive, that we are induced to follow it step by step. 
First, he ascertained by full and exact inquiries, all the facts of the 
ease as known to the miners. Secondly, he proceeded to learn 
more fully the properties of the agent which he was to attempt to con- 
trol. What is this fire-damp? He analyzed it and found it to be, 
as other chemists had said, a variety of carburetted hydrogen gas. 
What will kindle it? A red-hot iron will not—a burning coal will 
not. It therefore requires a higher degree of heat to inflame it, than 
most other explosive gaseous mixtures. And here an important in- 
ference met him, that if the gas, when on fire, were cooled, it would 
be extinguished. Again, carburetted hydrogen, by burning, produ- 
ces carbonic acid, and the atmospheric air with which it is mixed in 
the explosive compound, produces nitrogen ; and each of these pro- 
ducts, added to the explosive mixture, greatly impairs or even de- 
stroys its power of exploding ; and therefore, since these rise from a 
burning lamp, they would of themselves prevent the communication 
of the flame through the open chimney of the lamp. Under what 
circumstances does the fire-damp burn with explosion? ‘The general 
reply is, when mixed with air; but experiments were instituted to as- 
certain the effect of different proportions of air. One part of fire 
damp, and any portion of air less than four parts, burnt without ex- 
plosion.. Seven or eight of air to one of the other, constituted the 
most highly explosive mixture. In fifteen of air to one of fire-damp, 
a lamp burnt without explosion, and with the flame greatly enlarged. 
Through what channels (if there be any) between two separate por- 
tions of these explosive mixtures, will the flame when applied to one 
t of the explosion at the Felling Colliery, in the Annals 
of Philosophy for 1813. | 
Vou. XVII.—No. =; 4 
