n; and I myself
have seen it at work in the Shetland Islands, and even the north of
Scotland, though it is now done away with even there, still more farther
south, and its place supplied and its work done by overshot and
under-shot wheel-gear, and improved machinery attached, of less or more
complexity. One of the most recent improvements is the Turbine, a sort
of Barker's mill; it is of great power, small compass, and acts under a
good fall with a minimum expenditure of water-power.

Passing from the consideration of water as a motive power in its natural
state, I ask you to notice briefly the gigantic force it can be made to
develop under the action of heat. In its normal form the power of water
is due, as I have said, to its incompressibility; in the state of
vapour, to which it is reduced by heat, its power is due to the counter
force of expansion. It was when confined as a state prisoner in the
Tower of London that the Marquis of Worcester began to speculate on the
possibilities of steam, though he little dreamed of its more important
applications, and the incalculable services it might be made to render
to the cause of humanity. Suddenly, one day, his musings in his solitude
were interrupted by the rattling of the lid of a kettle, which was
boiling away on the fire beside him, when, being of a philosophic vein,
he commenced to inquire after the cause; and he soon reasoned himself
into the conclusion that the motive power lay in the tension of the
vapour, and that the maintenance of this must be due to successive
additions of heat. The thought was a seed sown in a fit soil, for it led
to experiments which confirmed the supposition, and inaugurated others
that have borne fruit, as we see. It was a great moment in the annals of
discovery, and from that time to this the genius of improvement has
moved onward with unprecedented strides; and this in the application of
steam-power as well as the results, stupendous as these last have been.
For as there is no department of industry that has not made immense
advances since, none on which steam has not directly or indirectly been
brought to bear with effect; so there has been no end to the ingenuity
and ingenious devices by which steam has been coaxed into subjection to
human use and made the pliant minister of the master, man. All these
results follow as a natural consequence from the first discovery of its
motive power by the Marquis of Worcester, and the subsequent invent