The West Arm extends down the west side of Adolphus Island for seven miles; it is then divided by a projecting point under View Hill; and, whilst one runs to the eastward and unites with the East Arm, the other continues to trend to the southward, and then opens out to an extensive basin eleven miles in length, and from four to six in breadth; and, at seven miles, gradually contracts as it winds under the base of the Bastion Hills: before, however, you arrive at the basin, the stream is divided by several islands and rocky islets, that narrow the channel in some parts to the width of half a mile, in which the depth is very great, and the tide runs with great strength.
At the entrance of the basin the high rocky character of the west shore is superseded by low mangrove banks, with here and there a detached hill rising from a plain of low marshy land, that, at the time of our visit, was covered with a salt incrustation, occasioned by the evaporation of the sea, which, apparently, had lately flooded the low lands to a great extent: some of these plains are seven and eight miles in diameter.

The hills rise abruptly; those we examined are of sandstone formation.

The basin is very shoal, but there is a narrow channel in the centre, with from five to nine fathoms water.

The shore, opposite the Bastion Hills, is low, and the gulf trends gradually round to the South-West for five miles, when it is contracted into a narrow communication, called The Gut, leading to an interior shoal basin, strewed with low marshy islands, which the tide covers.

This basin terminates to the southward in a narrow stream, winding under the base of Mount Cockburn; and there also appeared to be several others falling into the basin more to the westward.