) 
methods of lighting the mines without producing its explosion . 7 
sive power, was that of 7 or 8 parts of air to 1 of gas; but the 
report produced by 50 cubical inches of this mixture was less 
than that produced by T L of the quantity of a mixture of 2 
parts of atmospherical air and 1 of hydrogene. 
It was very important to ascertain the degree of heat 
required to explode the fire-damp mixed w ; ith its proper 
proportion of air. 
I found that a common electrical spark would not explode 5 
parts of air and 1 of fire-damp, though it exploded 6 parts of 
air and 1 of damp : but very strong sparks from the discharge 
of a Leyden jar, seemed to have the same power of exploding 
different mixtures of the gas as the flame of the taper. 
Well burned charcoal, ignited to the strongest red heat, did 
not explode any mixture of air and of the fire-damp ; and a 
fire made of well burned charcoal, i. e. charcoal that burned 
without flame, was blown up to whiteness by an explo- 
sive mixture containing the fire-damp, without producing its 
inflammation. An iron rod at the highest degree of red heat, 
and at the common degree of white heat, did not inflame ex- 
plosive mixtures of the fire-damp ; but, when in brilliant com- 
bustion, it produced the effect. 
The flame of gaseous oxide of carbon as well as of olefiant 
gas exploded the mixtures of the fire-damp. 
In respect of combustibility, then, the fire-damp differs most 
materially from the other common inflammable gases. 
Olefiant gas, which I have found explodes mixed in the same 
proportion with air, is fired by both charcoal and iron heated 
to dull redness. Gaseous oxide of carbon, which explodes 
when mixed with 2 parts of air, is likewise inflammable by 
red hot iron and charcoal. And hydrogene, which explodes 
when mixed with j- of its volume of air, takes fire at the lowest 
