possible.
The miner could not live in a place filled with this injurious gas, any
more than one could live in a gasometer full of common gas. Moreover,
fire-damp, as well as the latter, a mixture of inflammable gases, forms
a detonating mixture as soon as the air unites with it in a proportion
of eight, and perhaps even five to the hundred. When this mixture is
lighted by any cause, there is an explosion, almost always followed by a
frightful catastrophe.

As they walked on, Simon Ford told the engineer all that he had done
to attain his object; how he was sure that the escape of fire-damp
took place at the very end of the farthest gallery in its western part,
because he had provoked small and partial explosions, or rather little
flames, enough to show the nature of the gas, which escaped in a small
jet, but with a continuous flow.

An hour after leaving the cottage, James Starr and his two companions
had gone a distance of four miles. The engineer, urged by anxiety and
hope, walked on without noticing the length of the way. He pondered
over all that the old miner had told him, and mentally weighed all the
arguments which the latter had given in support of his belief. He agreed
with him in thinking that the continued emission of carburetted hydrogen
certainly showed the existence of a new coal-seam. If it had been merely
a sort of pocket, full of gas, as it is sometimes found amongst the
rock, it would soon have been empty, and the phenomenon have ceased.
But far from that. According to Simon Ford, the fire-damp escaped
incessantly, and from that fact the existence of an important vein might
be considered certain. Consequently, the riches of the Dochart pit were
not entirely exhausted. The chief question now was, whether this was
merely a vein which would yield comparatively little, or a bed occupying
a large extent.

Harry, who preceded his father and the engineer, stopped.

"Here we are!" exclaimed the old miner. "At last, thank Heaven! you
are here, Mr. Starr, and we shall soon know." The old overman's voice
trembled slightly.

"Be calm, my man!" said the engineer. "I am as excited as you are, but
we must not lose time."

The gallery at this end of the pit widened into a sort of dark cave.
No shaft had been pierced in this part, and the gallery, bored into the
bowels of the earth, had no direct communication with the surface of the
earth.

James Starr, with intense interest, examined the place in which the