222 
COLLIEKY EXPLOSIONS. 
1845, Faraday and Lyell^ pointed out, that after an explosion 
coal dust was found adhering to the props and sides of the 
galleries of the mine. Similar observations were published by 
M. du Souich ten years later, and some observations were carried 
out by M. Verpilleux, in 1867, on the same subject. It is, 
however, to Mr. William Gallaway, mining engineer, of Cardiff, 
and formerly one of Her Majesty’s Assistant Inspectoi’s of 
Mines, to whom most credit is due for bringing to notice the 
fact that coal dust is a factor in colliery explosions. The result 
of Mr. Callaway’s observations seems to be that coal dust is a 
very considerable factor, if not the chief, and that air contami- 
nated with fire-damp and dry coal dust becomes explosive, even 
though the gas might be present in so small a quantity as not to 
be detected by the methods adopted in practical mining. Mr. 
Callaway finds that^ “ a mixture of fire-damp and air, in the 
proportion of 1 volume of the former to 60, or more, volumes of 
the latter, give no reliable indication of the presence of inflam- 
mable gas when tested in the manner usually, if not always, 
adopted in mines.” “ 2nd. A mixture of fire-damp and air, in 
the proportion of 1 volume of the former to 112 of the latter, 
becomes inflammable at ordinary pressure and temperature, 
when charged with fine coal dust.” These experiments of Mr. 
Callaway’s seem to solve the problem presented by the evidence 
gathered as to the cause of several explosions, namely, that 
previous to the calamity, the mine has been pronounced free 
from gas.® 
A series of investigations have also been made, at the request 
1 Phil, Mag., 1845. 
2 Proc. Boyal Society, No. 168, 1876, p. 364. 
3 In the Annals of Mines, 1875, M. Vital refers to an explosion 
in the Campagnac Colliery, where no fire-damp had been previously 
discovered. 
