Rottnest Island, 6 miles in length E. by N. and W. by S. with an extreme breadth of 2½ miles, has an irregular hummocky surface, not much wooded, and may now be distinguished from Garden Island and the contiguous main land by a white obelisk, 15ft. in height, with a pole in the middle, of the same length, which has recently been erected on its highest part near the centre of the Island. This sea-mark, being elevated about 157ft. above the level of the sea, may be seen from a ship's deck in clear weather at the distance of 7 or 8 leagues, and will shortly give place to a lighthouse of greater elevation. Its position, according to observations in H.M.S. Beagle, is lat. 32d. 0m. 14s. South, long. 115d. 29m. 6s. East from Greenwich.
To round the Island on its north side, a ship should not approach nearer than one mile, in order to avoid the Horseshoe Rock which lies ¾ of a mile off shore, at the distance of two miles N. 396. E. from the Island's west extremity, and Roe's Reef situate ¾ of a mile N. 16 deg. W. from a small rock with a cask beacon upon it, about half a cable's length from the island's N.E. point. The beacon is upon Duck Rock, and the projection near it is Bathurst Point. A ship will be clear to the northward of Horse-shoe Rock while Duck Rock beacon is kept open of the N. point of Rottnest; and Roe's Reef may be cleared on the north by keeping the west end of Rottnest (Cape Vlaming) open of the north point, until Duck Rock bears south; a course may then be shaped about E. by S. for a remarkable white sand patch on the main, which will be distinctly visible 3½ miles north from the entrance to Swan river; and when some rocky islets near the S.E. side of Rottnest are seen to the SSW., opening near the east end of another small rock with a cask[?] beacon upon it 1¼ mile SE½E from Duck Rock, a SE by E course will conduct in Gage's Roads.
Kingston Spit, in front of Thompson's Bay, extends 2 miles east from Duck Rock, and a long mile NE by E from the beacon last mentioned, which has recently been placed upon Fisherman's Rock, a small mass of white rocks about 2 cables length NE from the sandy east point of Rottnest Island, distinguished by the name of Point Philip. To clear Kingston Spit on the north, keep Duck Rock a little shut in to the south of a bare pointed hill near the northern shore of Rottnest; or should the bare hill not be distinguished, keep the north extreme of Rottnest to the southward of W½S; and to clear Kingston Spit on the south, keep the south extreme of Rottnest (Point Parker) open of the next projection to the N.E. of it (S.W. by W.)
Thompson's Bay is a fit resort for boats only, being full of shoal rocky patches and sand banks, to the distance of a mile from the shore,—the remainder of Kingston Spit being occupied by foul uneven ground, with depths varying between 5 and 2 fathoms; near its north and east edges are 7 fathoms, deepening to 9 and 10 in ½ a mile. Between Point Philip and the next projection along ½ mile to the SSW (Bickley Point) there is good shelter in Beagle's Anchorage from all the usual NW and SW gales of winter, the best birth being in 4 fathoms water, sandy ground, nearly ½ a mile south from Fisherman's Rock, and a ¼ of a mile NE from two small rocks called the Twins,—the south point of Rottnest being also in a line with Bickley Point. In this situation a vessel should moor, on account of the limited space.