appearance, and they rose abruptly from a smooth surface, strewed with
rolled debris of organic remains, to a height of about twenty feet. The
Officier du Roi, in his most interesting tour in 1768 round the island, has
described masses of upraised coral-rocks, still retaining that moat-like
structure (see my "Coral Reefs") which is characteristic of the living
reefs. On the coast northward of Port Louis, I found the lava concealed for
a considerable space inland by a conglomerate of corals and shells, like
those on the beach, but in parts consolidated by red ferruginous matter. M.
Bory St. Vincent has described similar calcareous beds over nearly the
whole of the plain of Pamplemousses. Near Port Louis, when turning over
some large stones, which lay in the bed of a stream at the head of a
protected creek, and at the height of some yards above the level of spring
tides, I found several shells of serpula still adhering to their under
sides.

The jagged mountains near Port Louis rise to a height of between two and
three thousand feet; they consist of strata of basalt, obscurely separated
from each other by firmly aggregated beds of fragmentary matter; and they
are intersected by a few vertical dikes. The basalt in some parts abounds
with large crystals of augite and olivine, and is generally compact. The
interior of the island forms a plain, raised probably about a thousand feet
above the level of the sea, and composed of streams of lava which have
flowed round and between the rugged basaltic mountains. These more recent
lavas are also basaltic, but less compact, and some of them abound with
feldspar, so that they even fuse into a pale coloured glass. On the banks
of the Great River, a section is exposed nearly five hundred feet deep,
worn through numerous thin sheets of the lava of this series, which are
separated from each other by beds of scoriae. They seem to have been of
subaerial formation, and to have flowed from several points of eruption on
the central platform, of which the Piton du Milieu is said to be the