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 twenty years after, viz., in 1885, this had increased to no less than 159 millions, such were the giant strides which the increase in consumption made.

In the return for 1892, this amount had farther increased to 181-1/2 millions of tons, an advance in eight years of a quantity more than equal to the total raised in 1820, and in 1894 the total reached 199-1/2 millions; this was produced by 795,240 persons, employed in and about the mines.

CHAPTER VIII.

THE COAL-TAR COLOURS.

In a former chapter some slight reference has been made to those bye-products of coal-tar which have proved so valuable in the production of the aniline dyes.  It is thought that the subject is of so interesting a nature as to deserve more notice than it was possible to bestow upon it in that place.  With abstruse chemical formulae and complex chemical equations it is proposed to have as little as possible to do, but even the most unscientific treatment of the subject must occasionally necessitate a scientific method of elucidation.

The dyeing industry has been radically changed during the last half century by the introduction of what are known as the artificial dyes, whilst the natural colouring matters which had previously been the sole basis of the industry, and which had been obtained by very simple chemical methods from some of the constituents of the animal kingdom, or which were found in a natural state in the vegetable kingdom, have very largely given place to those which have been obtained from coal-tar, a product of the mineralised vegetation of the carboniferous age.