simple reason
being that electric power storage--apart from the special purposes of
the subdivision and transmission for lighting--has not yet been tried
on a large scale. For the regulation and graduation of power it is
exceedingly handy to be able to "switch-on" a number of small
accumulator cells for any particular purpose; and, of course, the
degree of control held in the hands of the engineer must depend
largely on the smallness of each individual cell, and the number which
he has at command. This fact of itself tends to keep down the size of
the storage cell which is most popular.

But when power storage by means of the electric accumulator really
begins in earnest the cells will attain to what would at present be
regarded as mammoth proportions; and the special purpose aimed at in
each instance of power installation will be the securing of
continuity in the working of a machine depending upon some
intermittent natural force. Windmills are especially marked out as the
engines which will be used to put electrical energy into the
accumulators. From these latter again the power will be given out and
conveyed to a distance continuously.

High ridges and eminences of all kinds will in the future be selected
as the sites of wind-power and accumulator plants. In the eighteenth
century, when the corn from the wheat-field required to be ground into
flour by the agency of wind-power, it was customary to build the mill
on the top of some high hill and to cart all the material laboriously
to the eminence. In the installations of the future the power will be
brought to the material rather than the material to the power. From
the ranges or mountain peaks, and also from smaller hills, will
radiate electrical power-nerves branching out into network on the
plains and supplying power for almost every purpose to which man
applies physical force or electro-chemical energy.

The gas-engine during the twentieth century will vigorously dispute
the field against electrical storage; and its success in the
struggle--so far as regards its own particular province--will be
enhanced owing to the fact that, in some respects, it will be able to
command the services of electricity as its handmaid. Gas-engines are
already very largely used as the actuators of electric lighting
machinery. But in the developments which are now foreshadowed by the
advent of acetylene gas the relation will be reversed. In other words,
the gas-engine will owe its