COLLIERY EXPLOSIONS. 
22B 
of the Secretary of State, with a view of farther investigating 
the influence of coal dust in colliery explosions.^ Among the 
points of interest elicited by this inquiry were the following : — 
The proportion of fire-damp required to bring dust in a mine 
into operation as a rapidly-burning or an exploding agent, even 
on a small scale, and with the application of a small source of 
heat or flame, is below the smallest amount which can be 
detected in the air of a mine by the experienced observer, with 
the means at present used. In air travelling at a velocity of 
600 feet per minute, different coal dusts suspended in the air, 
containing from 2 to 2’75 per cent, of fire-damp, produce 
explosions, At a velocity of 100 feet per minute, the same 
result was obtained with air containing only 1-5 per cent, of 
gas ; and ignitions of dust approaching explosions and extending 
to considerable distances were obtained with dust in air con- 
taining much smaller proportions of gas. Mixtures of fire-damp 
and air, bordering on those which will ignite on the approach of 
flame, were instantaneously inflamed by a lamp when only a few 
particles of dust were in suspension. 
The preventative against this influence of coal dust suggested 
by Mr. Gallaway and M. Vital is to water the road-ways, 
w’hereby the dust would be laid. The objection to this is, that 
the wet causes a disturbance of the ground ; the bottom rises up, 
and is liable to bring about serious consequences. However, 
we have the choice of two evils, the rising of the floor caused 
by the water, or the choice of an explosion. The question is, 
which is the lesser of the two evils? I should not hesitate to 
decide in favour of the watering. 
Notwithstanding what has been said as to the influence of 
coal dust in bringing about explosions, I am still of the opinion 
that atmospheric variations do facilitate explosions. This opinion 
^ Colliery Guardian, Oct. 28, 1881. 
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