en recombine and
supply force, either in intermittent thrusts at a piston, or as an
electric current, would be infinitely more convenient for all locomotive
purposes than the cumbersome bunkers and boilers required by steam. The
presumption is altogether in favour of the possibility of such
substances. Their advent will be the beginning of the end for steam
traction on land and of the steam ship at sea: the end indeed of the Age
of Coal and Steam. And even with regard to steam there may be a curious
change of method before the end. It is beginning to appear that, after
all, the piston and cylinder type of engine is, for locomotive
purposes--on water at least, if not on land--by no means the most
perfect. Another, and fundamentally different type, the turbine type, in
which the impulse of the steam spins a wheel instead of shoving a
piston, would appear to be altogether better than the adapted pumping
engine, at any rate, for the purposes of steam navigation. Hero, of
Alexandria, describes an elementary form of such an engine, and the
early experimenters of the seventeenth century tried and abandoned the
rotary principle. It was not adapted to pumping, and pumping was the
only application that then offered sufficient immediate encouragement to
persistence. The thing marked time for quite two centuries and a half,
therefore, while the piston engines perfected themselves; and only in
the eighties did the requirements of the dynamo-electric machine open a
"practicable" way of advance. The motors of the dynamo-electric machine
in the nineteenth century, in fact, played exactly the _role_ of the
pumping engine in the eighteenth, and by 1894 so many difficulties of
detail had been settled, that a syndicate of capitalists and scientific
men could face the construction of an experimental ship. This ship, the
_Turbinia_, after a considerable amount of trial and modification,
attained the unprecedented speed of 341/2 knots an hour, and His Majesty's
navy has possessed, in the _Turbinia's_ younger and greater sister, the
_Viper_, now unhappily lost, a torpedo-destroyer capable of 41 miles an
hour. There can be little doubt that the sea speeds of 50 and even 60
miles an hour will be attained within the next few years. But I do not
think that these developments will do more than delay the advent of the
"explosive" or "storage of force" engine.

[7] The historian of the future, writing about the nineteenth century,
will, I sometimes f