ward of the Cape, was 245 miles in 24 hours, or lOf nearly
in each hour. The prevailing southerly winds in these latitudes,
during the summer months, are no doubt occasioned
by a strong current of condensed air rushing from regions of
ice towards the more rarefied atmosphere of Southern Africa;
where the vapour with which it is loaded, by a change of
temperature, and by concussion against the high mountainous
promontory of the Cape, is discharged ; and subsides in that
singular fleecy cloud which envelopes the summit of the
Table mountain, continuing for several days together whenever
the south-easterly wind prevails.
On the 1st of February we discovered the two islands of
St. Paul and Amsterdam, and on the evening of the same
day anchored on the eastern side of the latter, at the distance
of about a mile from the shore. The volumes of smoke
which we had perceived at a distance to ascend from the
island, and the flames which, when dark, were seeii distinctly
to issue from it, excited in us a strong desire to get
on shore; and accordingly before it was well light the next
morning we quitted the vessel, elate with the hope of gratifying
curiosity by some novel spectacle. Of the result of our
observations the following is a brief sketch. The island of
Amsterdam, which lies in latitude 38° 42' south, and longitude
76° 51' east, is, in its greatest extent, about four miles
and a quarter from north to south, and two and a quarter
from east to west, containing seven or eight square miles of
surface, exclusive of a large volcanic crater, into which the
sea has forced a passage on the eastern side, by the incessant
action of its waves rolling with an uninterrupted current from
that quarter. The whole width of this breach is about a
thousand feet, but the channel, or that part of it'through
which the tide ebbs and flows, does not exceed two hundred
feet. From the margins of this channel two rising banks,
composed of volcanic fragments, are connected with the two
cheeks of the breach, whose height, by a rough trigonometrical
measurement, we found to be somewhere about seven
hundred feet, which may be considered as the general height
of the surrounding sides of the crater above the surface of
the water within it. The original form, as distinctly appears
by looking down from the upper edge, was that of an ellipsis ;
but the materials of the side, where the breach was made,
by being forced inwards by the sea, have caused on that side
of the crater a considerable compression or concavity. The
longest diameter across the surface of the water is somewhat
more than 1000 yards, and the shortest about 850; the cii-
cumference a mile and three quarters nearly; and as the
sides rise in an angle with the horizon of about 65 degrees,
the circuit of the upper edge or brim of the bason, supposing
it complete and that no breach had been made, would have
been rather more than two miles. We sounded about the
centre of the crater, and found the depth of water 174 feet,
which being added to the mean height of the sides above
water, gives 874 feet for the whole depth of the crater.
Every other part of the coast rises abruptly out of the sea,
like the wall-sided island of Tristan da Cunha, exhibiting the
successive strata of lava that have flowed down from the
upper ridge of the great crater; and the rugged and blistered
appearance sufficiently indicates the severe conflict that the