f 310 feet corresponds to five and
a half seconds. It is mentioned that the swing of the steam-ship
_Great Eastern_ took six seconds." Other authorities state that during
a storm in the Atlantic the velocity of the wave was determined to be
thirty-two miles an hour, and that nine or ten waves were included in
each mile; thus about five would pass in each minute. But in average
weather the number of waves to the mile is considerably larger, say,
from fifteen to twenty to the mile; and in nearly calm days about
double those numbers.

One interesting fact, which gives to wave-power a peculiarly enhanced
value as a source of stored wind-power, is that the surface of the
ocean--wild as it may at times appear--is not moved by such extremes
of agitation as the atmosphere. In a calm it is never so inertly
still, and in a storm it is never so far beyond the normal condition
in its agitation as is the wind. The ocean surface to some extent
operates as the governor of a steam-engine, checking an excess in
either direction. In very moderate weather the number of waves to the
mile is greatly increased, while their speed is not very much
diminished. Indeed the rate at which they travel may even be
increased.

This latter phenomenon generally occurs when long ocean rollers pass
out of a region of high wind into one of relative calm, the energy
remaining for a long time comparatively constant by reason of the
multiplication of short, low waves created out of long, high ones. On
all ocean coasts the normal condition of the surface is governed by
this law, and it follows that, no matter what the local weather may be
at any given time, there is always plenty of power available.

An attempt was made by M. C. Antoine, after a long series of
observations, to establish a general relation between the speed of the
wind and that of the waves caused by it, the formulae being published
in the _Revue Nautique et Coloniale_ in 1879. The rule may be taken as
correct within certain limits, although in calm weather, when the
condition of the ocean surface is almost entirely ruled by distant
disturbances, it has but little relevancy. Approximately, the velocity
of wave transmission is seven times the fourth root of the wind-speed;
so that when the latter is a brisk breeze of sixteen miles an hour the
waves will be travelling fourteen miles an hour, or very nearly as
fast as the wind. When, on the other hand, a light breeze of nine
miles an hour is d