the supplies of Great Britain would last.

This Commission reported in 1871, and the outcome of it was that a period
of twelve hundred and seventy-three years was assigned as the period
during which the coal would last, at the then-existing rate of
consumption. The quantity of workable coal within a depth of 4000 feet
was estimated to be 90,207 millions of tons, or, including that at
greater depths, 146,480 millions of tons. Since that date, however, there
has been a steady annual increase in the amount of coal consumed, and
subsequent estimates go to show that the supplies cannot last for more
than 250 years, or, taking into consideration a possible decrease in
consumption, 350 years. Most of the coal-mines will, indeed, have been
worked out in less than a hundred years hence, and then, perhaps, the
competition brought about by the demand for, and the scarcity of, coal
from the remaining mines, will have resulted in the dreaded importation
of coal from abroad.

In referring to the outcome of the Royal Commission of 1866, although the
Commissioners fixed so comparatively short a period as the probable
duration of the coal supplies, it is but fair that it should be stated
that other estimates have been made which have materially differed from
their estimate. Whereas one estimate more than doubled that of the Royal
Commission, that of Sir William Armstrong in 1863 gave it as 212 years,
and Professor Jevons, speaking in 1875 concerning Armstrong's estimate,
observed that the annual increase in the amount used, which was allowed
for in the estimate, had so greatly itself increased, that the 212 years
must be considerably reduced.

One can scarcely thoroughly appreciate the enormous quantity of coal that
is brought to the surface annually, and the only wonder is that there are
any supplies left at all. The Great Pyramid which is said by Herodotus to
have been twenty years in building, and which took 100,000 men to build,
contains 3,394,307 cubic yards of stone. The coal raised in 1892 would
make a pyramid which would contain 181,500,000 cubic yards, at the low
estimate that one ton could be squeezed into one cubic yard.

The increase in the quantity of coal which has been raised in succeeding
years can well be seen from the following facts.

In 1820 there were raised in Great Britain about 20 millions of tons. By
1855 this amount had increased to 64-1/2 millions. In 1865 this again had
increased to 98 millions, whilst