^78 MOLESWORTH'S POCKET-BOOK
W aves—continued.
4. Motion greatest at crest and at lowest portion
Ox trough; no motion at half height of wave
5. Power of destruction directly proportional to
height of wave, and greatest when crest breaks.
6. A wave of 10 feet high, 32 feet long, would
only agitate the water 6 inches at 10 feet below
the surface; a wave 10 feet high and 100 feet
long would only disturb the water 18 inches at the
same depth.
7. At a depth = the length of the wave, the
gotlon is diminished to of that at the sur-
8. A wave 30 feet high may exert a pressure of
nearly 1 ton per square foot of surface.
9. In exposed position, and in deep water,
13 ton may be exerted by waves striking suddenly
on a vertical surface. '
10 The height of a wave does not equal the
depth of water, but it nearly approaches that limit.
Velocity of Free Waves in Feet pek Second,
when the Length of Wave exceeds 1000
Depth.
Depth of Water in feet.
Depth .. 1 3 3 | 4 | 5 | 8 10 20 j 30
Velocity 5-? 8 9’8 I n jl2-6 | 16 18 25 1 31
Depth .. 40 60 80 100 1 200 I4OO 600 800 1000
Velocity ..
36 45 51 | 57 | 80 1113 j 139 1601 179