Lyell, similar movements of the sea have occurred at islands far
distant from the chief line of disturbance, as was the case with
Juan Fernandez during this earthquake, and with Madeira during the
famous Lisbon shock. I suspect (but the subject is a very obscure
one) that a wave, however produced, first draws the water from the
shore, on which it is advancing to break: I have observed that this
happens with the little waves from the paddles of a steam-boat. It
is remarkable that whilst Talcahuano and Callao (near Lima), both
situated at the head of large shallow bays, have suffered during
every severe earthquake from great waves, Valparaiso, seated close
to the edge of profoundly deep water, has never been overwhelmed,
though so often shaken by the severest shocks. From the great wave
not immediately following the earthquake, but sometimes after the
interval of even half an hour, and from distant islands being
affected similarly with the coasts near the focus of the
disturbance, it appears that the wave first rises in the offing;
and as this is of general occurrence, the cause must be general: I
suspect we must look to the line where the less disturbed waters of
the deep ocean join the water nearer the coast, which has partaken
of the movements of the land, as the place where the great wave is
first generated; it would also appear that the wave is larger or
smaller, according to the extent of shoal water which has been
agitated together with the bottom on which it rested.
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