watermark. In the calm waters of the lagoon, directly connected with a
great, and therefore stable ocean, it seems very improbable that a change
in the currents, sufficiently great to cause the water to eat into the land
on all sides, should have taken place within a limited period. From these
considerations I inferred, that probably the atoll had lately subsided to a
small amount; and this inference was strengthened by the circumstance, that
in 1834, two years before our visit, the island had been shaken by a severe
earthquake, and by two slighter ones during the ten previous years. If,
during these subterranean disturbances, the atoll did subside, the downward
movement must have been very small, as we must conclude from the fields of
dead coral still lipping the surface of the lagoon, and from the breakers
on the western shore not having yet regained the line of their former
action. The subsidence must, also, have been preceded by a long period of
rest, during which the islets extended to their present size, and the
living margin of the reef grew either upwards, or as I believe outwards, to
its present distance from the beach.

Whether this view be correct or not, the above facts are worthy of
attention, as showing how severe a struggle is in progress on these low
coral formations between the two nicely balanced powers of land and water.
With respect to the future state of Keeling atoll, if left undisturbed, we
can see that the islets may still extend in length; but as they cannot
resist the surf until broken by rolling over a wide space, their increase
in breadth must depend on the increasing breadth of the reef; and this must
be limited by the steepness of the submarine flanks, which can be added to
only by sediment derived from the wear and tear of the coral. From the
rapid growth of the coral in the channel cut for the schooner, and from the
several agents at work in producing fine sediment, it might be thought that
the lagoon would necessarily become quickly filled up. Some of this
sediment, however, is transported into the open sea, as appears from the