If the sea has risen, its rise must have taken place over the whole
world simultaneously, and it must have risen to the same height over all
parts of the coral zone. Grounds have been shown for the belief that the
general level of the sea may have been different at different times; it
has been suggested, for example, that the accumulation of ice about the
poles during one of the cold periods of the earth's history necessarily
implies a diminution in the volume of the sea proportioned to the amount
of its water thus permanently locked up in the Arctic and Antarctic
ice-cellars; while, in the warm periods, the greater or less
disappearance of the polar ice-cap implies a corresponding addition of
water to the ocean. And no doubt this reasoning must be admitted to be
sound in principle; though it is very hard to say what practical effect
the additions and subtractions thus made have had on the level of the
ocean; inasmuch as such additions and subtractions might be either
intensified or nullified, by contemporaneous changes in the level of the
land. And no one has yet shown that any such great melting of polar ice,
and consequent raising of the level of the water of the ocean, has taken
place since the existing atolls began to be formed.
In the absence of any evidence that the sea has ever risen to the extent
required to give rise to the encircling reefs and the atolls, Mr.
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