AMSTERDAM ISLAND. 141 
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, b}^ a rough trigonometri- 
cal measurement, we found to be some^vllere about seven 
hundred feet, which may be considered as the general height 
of the surroundino" sides of the crater above tlie surface of 
the water within it. The original form, as distinctl}^ 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 8jO ; the cir- 
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 
