Corals and coral islands.

SUBSIDENCE IN PACIFIC CORAL REGIONS.

365

reefs and islands of the Pacific? It is very evident that the
sinking of the Society, Samoan, and Hawaiian Islands has
been small compared with that required to submerge all the
lands on which the Paumotus and the other Pacific atolls rest.
One, two, or five hundred feet, could not have buried the
many peaks of these islands. Even the 1,200 feet of depression at the Gambier Group is shown to be at a distance from
the axis of the subsiding area. The groups of high islands
above mentioned contain summits from 4,000 to 14,000 feet
above the sea; and it is not probable that throughout this
large area, when the two hundred islands now sunken were
above the waves, there were none of them equal in altitude
to the mean of these heights, or 9,000 feet. Hence, however
moderate our estimate, there must still be allowed a sinking
of many thousand feet. Moreover, whatever estimate we
make that is within probable bounds, we shall not arrive at
a more surprising change of level than the continents show
that they have undergone; for since the Tertiary began (or
the preceding period, the Cretaceous, closed) more than 10,000
feet have been added to the Rocky Mountains, parts of the
Andes, and Alps, and 19,000 feet to part of the Himalayas.
Between the New Hebrides and Australia, the reefs and
islands mark out another area of depression, which may have
been simultaneously in progress. The long reef of one hundred and fifty miles from the north cape of New Caledonia,
and the wide barrier on the west, cannot be explained without supposing a subsidence of one or two thousand feet at the
least. The distant barrier of Australia is proof of great subsidence, even along the border of that continent. But the
greatest amount of sinking took place, in all probability, over
the intermediate sea, called the " Coral Sea," where there are
now a considerable number of atolls.