have descended. Their inner and steeper escarpments are ranged in an
irregular curve, which rudely follows the line of the shore, two or three
miles inland from it. I ascended a few of these hills, and from others,
which I was able to examine with a telescope, I obtained specimens, through
the kindness of Mr. Kent, the assistant-surgeon of the "Beagle"; although
by these means I am acquainted with only a part of the range, five or six
miles in length, yet I scarcely hesitate, from their uniform structure, to
affirm that they are parts of one great formation, stretching round much of
the circumference of the island.

The upper and lower strata of these hills differ greatly in composition.
The upper are basaltic, generally compact, but sometimes scoriaceous and
amygdaloidal, with associated masses of wacke: where the basalt is compact,
it is either fine-grained or very coarsely crystallised; in the latter case
it passes into an augitic rock, containing much olivine; the olivine is
either colourless, or of the usual yellow and dull reddish shades. On some
of the hills, beds of calcareous matter, both in an earthy and in a
crystalline form, including fragments of glossy scoriae, are associated
with the basaltic strata. These strata differ from the streams of basaltic
lava forming the coast-plains, only in being more compact, and in the
crystals of augite, and in the grains of olivine being of much greater
size;--characters which, together with the appearance of the associated
calcareous beds, induce me to believe that they are of submarine formation.

Some considerable masses of wacke, which are associated with these basaltic
strata, and which likewise occur in the basal series on the coast,
especially at Quail Island, are curious. They consist of a pale yellowish-
green argillaceous substance, of a crumbling texture when dry, but unctuous
when moist: in its purest form, it is of a beautiful green tint, with
translucent edges, and occasionally with obscure traces of an original