emote times these little separate heads or islets were joined, and
formed one continued and more elevated tract of land, which the sea, in
the revolution of ages, has washed away, leaving only the higher
grounds; which, in time also, will, according to this theory, share the
same fate. Another conjecture is, that they have been thrown up by
earthquakes, and are the effect of internal convulsions of the globe. A
third opinion, and which appears to me as the most probable one,
maintains, that they are formed from shoals or coral banks, and, of
consequence, increasing. Without mentioning the several arguments made
use of in support of each of these systems, I shall only describe such
parts of Palmerston's Island as fell under my own observation when I
landed upon it.

The foundation is every where a coral rock; the soil is coral sand, with
which the decayed vegetables have but in a few places intermixed, so as
to form any thing like mould. From this a very strong presumption may be
drawn, that these little spots of land are not of very ancient date, nor
the remains of larger islands now buried in the ocean; for, upon either
of these suppositions, more mould must have been formed, or some part of
the original soil would have remained. Another circumstance confirmed
this doctrine of the increase of these islets. We found upon them, far
beyond the present reach of the sea even in the most violent storms,
elevated coral rocks, which, on examination, appeared to have been
perforated in the same manner that the rocks are that now compose the
outer edge of the reef. This evidently shews that the sea had formerly
reached so far; and some of these perforated rocks were almost in the
centre of the land.

But the strongest proof of the increase, and from the cause we have
assigned, was the gentle gradation observable in the plants round the
skirts of the islands; from within a few inches of high-water mark to
the edge of the wood. In many places, the divisions of the plants of
different growths were very distinguishable, especially on the lee or
west side. This I apprehend to have been the operation of extraordinary
high tides, occasioned by violent, accidental gales from the westward,
which have heaped up the sand beyond the reach of common tides. The
regular and gentle operation of these latter, again, throw up sand
enough to form a barrier against the next extraordinary high tide or
storm, so as to prevent its reaching as far as