riving the waves, the latter, according to the
formula, should run about twelve and a half miles an hour; but, in
point of fact, the influence of more distant commotion nearly always
interferes with this result.

As a matter of experience, the waves on an ocean coast are usually
running faster than the wind, and, being so much more numerous in
calm than they are in rough weather, they maintain comparatively a
uniform sum total of energy. It is obvious that, so far as practical
purposes are concerned, three waves of an available height of three
feet each are as effective as one of nine feet. If the state of the
weather be such that the average wave length is 176 feet there will be
exactly thirty waves to the mile, and if the speed be twelve miles an
hour--that is to say, if an expanse of twelve miles of waves pass a
given point hourly--then 360 waves will pass every sixty minutes, or
six every minute. In the wave-power plant as described, each buoy of
one hundred tons displacement when raised and depressed, say, three
feet by every wave will thus be capable of giving power equal to three
times 600, or 1,800 foot-tons per minute.

The unit of nominal horse-power being 33,000 foot-pounds or about
fifteen foot-tons per minute, it is evident that each buoy, at its
maximum, would be capable of giving about 120 horse-power. Supposing
that half of the possible energy were exerted at the forward and half
at the backward stroke and that each buoy were always in position to
exert its full power upon the uprising shaft without deduction, the
total effective duty of a machine such as has been described would be
480 horse-power. In practice, however, the available duty would
probably, according to minor circumstances, be rather more or rather
less than 300 horse-power.

CHAPTER III.

STORAGE OF POWER.

The three principal forms of stored power which are now in sight above
the horizon of the industrial outlook are the electric storage
battery, compressed air, and calcium-carbide. The first of these has
come largely into use owing to the demand for a regulated and stored
supply of electricity available for lighting purposes. Indeed the
storage battery has practically rendered safe the wide introduction of
electric lighting, because a number of cells, when once charged, are
always available as a reserve in case of any failure in the power or
in the generators at any cen