t in the meantime his trade has been to a large extent
destroyed. For its revival there is no doubt that, as Lord Kelvin
remarked in the address already quoted, "the little thing wanted to
let the thing be done is cheap windmills."

This, however, leads to another part of the problem. The costliness of
the best modern patterns of windmill as now so extensively used,
particularly in America, is mainly due to the elaborate, and, on the
whole, successful attempts at minimising the objection of the
intermittent nature of the source of power. To put the matter in
another way, it may be said that lightness, and sensitiveness to the
slightest breeze, have had to be conjoined with an eminent degree of
safety in the severest gale, so that the most complicated
self-regulating mechanisms have been rendered absolutely imperative.
Once the principle of storage is applied, the whole of the conditions
in this respect are revolutionised. There is no need to attempt the
construction of wind-motors that shall run lightly in a soft zephyr of
only five or six miles an hour, and stability is the main desideratum
to be looked to.

The fixed windmill, which requires no swivel mechanism and no vane to
keep it up to the wind, is the cheapest and may be made the most
substantial of all the forms of wind-motor. In its rudimentary shape
this very elementary windmill resembles a four-bladed screw steam-ship
propeller. The wheel may be constructed by simply erecting a high
windlass with arms bolted to the barrel at each end, making the shape
of a rectangular cross. But those at one end are fixed in such
positions that when viewed from the side they bisect the angles made
by those at the other side. Sails of canvas or galvanised iron are
then fastened to the arms, the position of which is such that the
necessary obliquity to the line of the barrel is secured at once.

Looking at this elementary and at one time very popular form of
windmill, and asking ourselves what adaptation its general principle
is susceptible of in order that it may be usefully employed in
conjunction with a storage battery, we find, at the outset, that,
inasmuch as the electric generator requires a high speed, there is
every inducement to greatly lengthen the barrel and at the same time
to make the arms of the sails shorter, because short sails give in the
windmill the high rate of speed required.

We are confronted, in fact, with the same kind of problem which met
the cons