PART II.— GEOLOGY AND MINERALOGY. 
The map of the Island shows it to he a most irregular-shaped piece 
of land, with an extreme length from East to West of ten and a 
quarter miles, an extreme width from North to South of eight and 
a quarter miles, and having several small islets dotted here and 
there around its jagged coast. A high central ridge, varying in 
altitude from: two thousand to nearly three thousand feet, com- 
mences on the south-eastern side of the Island, and, taking a 
semicircular course towards the south-western side, separates the 
Island into two portions ; that portion to the south of the ridge 
takes the form of a huge bowl with its edge partly broken away, 
now known as Sandy Bay; whde that on the East, North, and W est, 
slopes gradually away, at angles varying from 8° to 10°, towards the 
sea, terminating at the coast line in perpendicular cliffs from 450 
to 2000 feet in height. This great wall of rock, which, on ap- 
proaching the Island from all but a southerly direction, seems to 
defy an entrance, is intersected by a number of deep and narrow 
gorges running at right angles from the coast line towards the 
central ridge, where they lessen considerably in depth and width. 
The only town is situated in one of these gorges on the north side 
of the Island ; it being one of the largest, may, probably, in some 
measure, account for its selection as a site for the fiist settlement. 
In size they vary considerably, and in some places lie close together, 
separated only by a narrow ridge several feet in width, while in 
others they are more than a mile apart. 
The soundings, which are of much value in computing the 
original line of coast, are quoted from a chart by Mr. George Thoms, 
of II.M.S. Northumberland, under the command of Bear-Admiral Sir 
George Cockburn, in the year IS 1 5 ; they show that the sea bottom 
slopes gradually to depths of 60 or 70 fathoms at a distance 
of about a mile and a half from the present coast, but immediately 
beyond that there appears to be no bottom recorded at a depth of, 
in some places, as much as 250 fathoms. It will be quite necessary 
