Scoresby has observed them 30 ft. high in the North Atlantic; and Ross
measured waves of 22 ft. in the South Atlantic. Wilkes records 32 ft.
in the Pacific. But the highest waves have been reported off the Cape
of Good Hope and Cape Horn, where they have been observed, on rare
occasions, from 30 to 40 ft high; and 36 ft. has been given as the
admeasurement in the Bay of Biscay, under very exceptional
circumstances. In the voyage round the world the Venus and Bonite
record a maximum of 27 ft., while the Novara found the maximum to be
35 ft. But waves of 12 to 14 ft. in shallow seas are often more trying
than those of larger dimensions in deeper water. It is generally
assumed that a distance from crest to crest of 150 to 350 ft. in the
storm wave gives a velocity (in the change of form) of from 17 to 28
miles per hour. But what is required in the computation of the
velocity is the period of passage between two crests. Thus a distance
of 500 to 600 ft. between two crests, and a period of 10 to 11
seconds, indicates a velocity of 34 miles per hour.

The following table, by Sir G.B. Airy (late Astronomer Royal), shows
the velocities with which waves of given lengths travel in water of
certain depth:

Depth of | Length of the Wave in Feet.[1]
the Water| | | | | | |
in Feet. | 10 | 100 | 1,000 | 10,000 | 100,000 |1,000,000 |10,000,000
---------+-----+------+-------+--------+---------+----------+----------
|
| Corresponding Velocity of Wave per Hour in Nautical Miles.
|
1 | 3.2 | 3.4 | 3.4 | 3.4 | 3.4 | 3.4 | 3.4
10 | 4.3 | 10.1 | 10.7 | 10.8 | 10.8 | 10.8 | 10.8