26 min Every
variation of the tides in the Southern Ocean is accurately
reproduced in every sea connected with it.
Wave motion consists only in a vertical movement of the
particles of water by which a crest and trough is formed
alternately, the crest being as much above the normal
horizontal line as the trough is below it; and in the tidal
waves this motion extends through the whole depth of the water
from the surface to the bottom, but there is no horizontal
movement except of form. The late Mr. J. Scott Russell
described it as the transference of motion without the
transference of matter; of form without the substance; of force
without the agent.
The action produced by the sun and moon jointly is practically
the resultant of the effects which each would produce
separately, and as the net tide-producing effect of the moon is
to raise a crest of water 1.4 ft above the trough, and that of
the sun is 0.6 ft (being in the proportion of I to 0.445), when
the two forces are acting in conjunction a wave 1.4 + 0.6 = 2
ft high is produced in the Southern Ocean, and when acting in
opposition a wave 1.4 - 0.6 = 0.8 ft high is formed. As the
derivative wave, consisting of the large mass of water set in
motion by the comparatively small rise and fall of the primary
wave, is propagated through the branch oceans, it is affected
by many circumstances, such as the continual variation in width
between the opposite shores, the alterations in the depth of
the channels, and the irregularity of the coast line.
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