The Malay Archipelago, Volume 1 _ The Land - Alfred Russel Wallace

rumbling noise, and at the same time the house shook slightly. Thinking it might
be thunder, I asked, "What is that?" "It is an earthquake," answered Inchi Daud,
my host; and he then told me that slight shocks were occasionally felt there, but
he had never known them to be severe. This happened on the day of the last
quarter of the moon, and consequently when tides were low and the surf usually
at its weakest. On inquiry afterwards at Ampanam, I found that no earthquake
had been noticed, but that on one night there had been a very heavy surf, which
shook the house, and the next day there was a very high tide, the water having
flooded Mr. Carter's premises, higher than he had ever known it before. These
unusual tides occur every now and then, and are not thought much of; but by
careful inquiry I ascertained that the surf had occurred on the very night I had
felt the earthquake at Labuan Tring, nearly twenty miles off. This would seem to
indicate, that although the ordinary heavy surf may be due to the swell of the
great Southern Ocean confined in a narrow channel, combined with a peculiar
form of bottom near the shore, yet the sudden heavy surfs and high tides that
occur occasionally in perfectly calm weather, may be due to slight upheavals of
the ocean-bed in this eminently volcanic region.