n, considerable quantities of sea-weed
had lodged, temporarily at least; but none of it appeared to have found
its way to this particular place. Nakedness and dreariness were the two
words which best described the island; the only interruption to its
solitude and desolation being occasioned by the birds, which now came
screaming and flying above the heads of the intruders, showing both by
their boldness and their cries, that they were totally unacquainted with
men.

The mound, in the centre of the reef, was an object too conspicuous to
escape attention, and our adventurers approached it at once, with the
expectation of getting a better look-out from its summit, than that they
had on the lower level of the surface of the ordinary reef. Thither then
they proceeded, accompanied by a large flight of the birds. Neither Mark
nor Bob, however, had neglected to turn his eyes towards the now
distant ship, which was apparently riding at its anchor, in exactly the
condition in which it had been left, half an hour before. In that
quarter all seemed right, and Mark led the way to the mount, with active
and eager steps.

On reaching the foot of this singular elevation, our adventurers found
it would not be so easy a matter as they had fancied, to ascend it.
Unlike the rest of the reef which they had yet seen, it appeared to be
composed of a crumbling rock, and this so smooth and perpendicular as to
render it extremely difficult to get up. A place was found at length,
however, and by lending each other a hand, Mark and Bob finally got on
the summit. Here a surprise was ready for them, that drew an exclamation
from each, the instant the sight broke upon him. Instead of finding an
elevated bit of table-rock, as had been expected, a circular cavity
existed within, that Mark at once recognised to be the extinct crater of
a volcano! After the first astonishment was over, Mark made a close
examination of the place.

The mound, or barrier of lava and scoriae that composed the outer wall of
this crater, was almost mathematically circular. Its inner precipice was
in most places absolutely perpendicular, though overhanging in a few;
there being but two or three spots where an active man could descend in
safety. The area within might contain a hundred acres while the wall
preserved a very even height of about sixty feet, falling a little below
this at the leeward side, where there existed one narrow hole, or
passage, on a level with the botto