613 
black damp, or even common air, and it will make its way up 
to the roof, whilst black damp will lie near the floor. 
Fire Damp requires twice its volume of pure oxj^gen 
for complete combustion. The three volumes of mixed gases 
after detonation are condensed into one volume; they yield 
one volume of carbonic acid, and two volumes of steam, which 
are immediately condensed. Now carbonic acid contains its 
own bulk of oxygen, it therefore represents one of the two 
volumes of oxygen which disappear, whilst the other volume 
of oxygen has united with two volumes of hydrogen and 
formed water. Light carburetted hydrogen must, conse- 
quently, contain twice its volume of hydrogen condensed with 
its own bulk of carbon vapour into the space of one volume. 
Thus, from the composition of fire damp, it is obvious that 
the gas in exploding renders ten times its bulk of atmospheric 
air unfit for respiration. The two volumes of oxygen which 
ten volumes of air contain, producing one volume of carbonic 
acid, and two volumes of steam, which becomes condensed, 
leaving eight volumes of nitrogen at liberty. Fire Damp 
from different localities has been frequently analyzed, and 
exhibits a general uniformity in composition, consisting 
principally of light carburetted hydrogen, with varying 
quantities of carbonic acid, nitrogen, hydrogen, atmospheric 
air, and sometimes olefiant gas, and sulphuretted hydrogen. 
Analysis of Fire Damp by Professor Playfair : — Light car- 
buretted hydrogen, 92 "80 ; nitrogen, 6*90 ; oxygen, 0*60 ; 
carbonic acid, 0*30 ; total, 100*60. 
THE SAFETY LAMP. 
The Safety Lamp is a valuable instrument in the hands of 
a competent person who thoroughly understands its use in 
testing for the presence of fire damp in coal mines, but the 
miner actually at work cannot be supposed to be at liberty to 
pay that nicety of attention to its indications that would 
appear desirable, but they ought to remember that the lamps 
