e where, if one may so speak, the main line is
reached, and then formed into trains, and taken to the shaft by means of
an endless rope worked by an engine in the pit. In accomplishing all
this work, great care has to be taken that the current of air is not
changed or stopped. This is effected by means of doors placed in various
parts of the mine, so as to stop the current and drive it in the
required direction. These doors are kept by boys, whose duty it is to
open and close them for the passage of the coal tubs. Those boys are
often allowed no light, and sit in a hole cut in the side of the road
near to the doors. Upon their carefulness the safety of the mine in a
great measure depends, as if they neglect to shut the door the current
of air is changed. I have been told that these boys are subject to
accidents no less than the workers, for, sitting in the dark, and often
alone for hours, they are very apt to go to sleep. To ensure being awoke
at the proper time, they frequently lie down on the line of rails under
the rope, so that when the rope is started it may awake them by its
motion, but at times so sound is their sleep, that it has failed to
rouse them in time, and a train of coal waggons has passed over them,
causing in most cases death.

The coal having been brought to the pit-mouth, it remains to be shown
what becomes of this most valuable mineral, the consumption of which is
now so large in all parts of the globe. The next person employed in the
trade is the sailor, to convey it to the market, and the collier vessels
are a valuable navy to the country, proving quite a nursery of seamen
for our royal marine service. Newcastle, Sunderland, West Hartlepool,
and a large number of other ports along our coast, have an immense
amount of shipping employed exclusively in the coal trade--no less than
5359 vessels carrying coal having entered the port of London alone in
1873, and the average annual quantity of coal exported abroad during the
three years ending 1872 was 12,000,000 tons.

I will not now detain you longer on the subject of the extent and
working of coal, lest I should tire your patience; but before concluding
I should wish to give some account of the uses to which this most
valuable product is applied. The main use of coal, as we all know, is to
produce heat, without which many a paterfamilias would grumble when the
dinner-hour came and he had nothing hot to eat. It not only, however,
supplies heat, but th