344 
MINERALS. 
money in his mouth, or rubbing it between his 
fingers, it immediately became as white as if it had 
been washed over with that metal. In such a 
situation it is not surprising that the workmen 
should be frequently destroyed, and that sooner or 
later most of them should be killed ; but it is a 
matter of much astonishment that men should be 
found, who for a trifling reward will expose them- 
selves to almost certain death while they can get 
employment of a less hazardous nature. 
Among the formidable evils which miners in 
general have to contend with, may be reckoned the 
noxious gases which are found in mines. These 
are chiefly inflammable air (hydrogenous gas) and 
fixed air (carbonic acid gas) ; they are both very 
dangerous companions where they abound, and are 
equally fatal, though they act in different ways. 
The former frequently plays upon the surface of 
the water which is found at the bottom of some 
mines, and immediately takes fire when a torch is 
presented to it. If the quantity is small the con- 
sequences are not to be dreaded ; but if it abounds, 
as is the case in some mines, and a light be inadver- 
tently brought near, the whole explodes with the 
violence of gunpowder, and blows every thing be- 
fore it. On this account steel mills have been in- 
troduced into mines, which give out sparks of fire 
in sufficient abundance for the workmen to see by 
without running any hazard, as inflammable air will 
not explode from a spark of this sort. 
Fixed air is of a nature directly opposite to that 
