Besides the increase of dry land, indicated by the foregoing facts, the
exterior solid reef appears to have grown outwards. On the western side of
the atoll, the "flat" lying between the margin of the reef and the beach,
is very wide; and in front of the regular beach with its conglomerate
basis, there is, in most parts, a bed of sand and loose fragments with
trees growing out of it, which apparently is not reached even by the spray
at high water. It is evident some change has taken place since the waves
formed the inner beach; that they formerly beat against it with violence
was evident, from a remarkably thick and water-worn point of conglomerate
at one spot, now protected by vegetation and a bank of sand; that they beat
against it in the same peculiar manner in which the swell from windward now
obliquely curls round the margin of the reef, was evident from the
conglomerate having been worn into a point projecting from the beach in a
similarly oblique manner. This retreat in the line of action of the
breakers might result, either from the surface of the reef in front of the
islets having been submerged at one time, and afterward having grown
upwards, or from the mounds of coral on the margin having continued to grow
outwards. That an outward growth of this part is in process, can hardly be
doubted from the fact already mentioned of the mounds of Porites with their
summits apparently lately killed, and their sides only three or four inches
lower down thickened by a fresh layer of living coral. But there is a
difficulty on this supposition which I must not pass over. If the whole,
or a large part of the "flat," had been formed by the outward growth of the
margin, each successive margin would naturally have been coated by the
Nulliporae, and so much of the surface would have been of equal height with
the existing zone of living Nulliporae: this is not the case, as may be
seen in the woodcut. It is, however, evident from the abraded state of the
"flat," with its original inequalities filled up, that its surface has been
much modified; and it is possible that the hinder portions of the zone of
Nulliporae, perishing as the reef grows outwards, might be worn down by the