f iron which had lain side by side with it in the northern counties,
but which had lain there unworked through the scarcity of wood, which
was looked upon as the only fuel by which it could be smelted. In the
middle of the eighteenth century a process for smelting iron with coal
turned out to be effective; and the whole aspect of the iron-trade was
at once revolutionized. In fifty years the annual production of iron in
Great Britain rose from under twenty thousand to more than one hundred
and seventy thousand tons. During the fifty years that followed it rose
to six millions of tons. Iron was to become the working material of the
modern world; and it is its production of iron which more than all else
has placed England at the head of industrial Europe. But iron was not
the only metal which coal drew from the soil to swell the national
wealth. The increase in its production was rivalled by that of lead,
copper, and tin; and the "mining districts" soon gathered a population
which raised them into social as well as economical importance.

[Sidenote: The Steam Engine.]

But it was not in its direct application to metallurgy that coal was
destined to produce its most amazing effects. What was needed to turn
England into a manufacturing country was some means of transforming the
force stored up in coal into a labour force; and it was this
transformation which was now brought about through the agency of steam.
Engines in which steam was used as a means of draining mines had long
been in use; but the power relied on was mainly that of the weight of
the air pressing on a piston beneath which a vacuum had been created by
the condensation of steam; and the economical use of such engines was
checked by the waste of fuel which resulted from the cooling of the
cylinder at each condensation, and from the expenditure of heat in again
raising it to its old temperature before a fresh stroke of the piston
was possible. Both these obstacles were removed by the ingenuity of
James Watt. Watt was a working engineer at Glasgow, whose mind had for
some time been bent on the improvement of the steam-engine; but it was
not till the spring of 1765, amidst the political turmoil which
characterized the early reign of George the Third, that as he strolled
on a Sunday afternoon across the Green of Glasgow the means of effecting
it burst on him. "I had gone," he says, "to take a walk on a fine
Sabbath afternoon. I had entered the Green by the gate at t