In the wider parts of Armstrong’s Channel there are many shoals of sand on each side, but a passage of sufficient width and depth is swept out by the tides, for ships to go through in safety.  The bottom is either rocky or sandy:  rocky in the deep and narrow parts, where the tides run three or four miles in an hour; and sandy in the bights and shoaler places.  The sand of the beaches is mostly granitic, but it sometimes consists of black metallic particles, such as are found in the stone of the islands.

It was not until Feb. 25 that the remains of the Sydney-Cove’s cargo were all on board, and that a favourable change in the wind permitted us to sail for Port Jackson.  These four days of detention enabled me to continue the survey along the south side of Preservation Island, and as far as the Bay of Rocks upon that of Cape Barren.  A meridian altitude from the south horizon, observed under more favourable circumstances than two others before taken, gave 40 deg. 28’ for the latitude of Hamilton’s Road.  The longitude is 19’ 20” west of Cape Barren; and therefore should be 148 deg. 6’ east of Greenwich.  It is high water in the road, according to Mr. Hamilton’s report, half an hour before the moon passes over the meridian; but from what I observed, without paying particular attention to it, the tide did not appear to flow so late by an hour:  the medium rise was about seven feet, as at Port Jackson.

Well tasted fresh water is collected, at certain seasons, in small pools near the east end of Preservation Island; but that which drains from the rocks was first used by the Sydney-Cove’s crew, until several of them died.  Small runs or pools of water are to be found almost every where under the high parts of Cape-Barren Island, and it is probable there may be some upon Clarke’s Island; but at the Passage Isles we found it difficult to obtain wherewithal to satisfy our thirst.

The stone of which the southern, and probably the whole of Furneaux’s Islands are composed, is mostly a whitish granite, but sometimes inclining to red; and is full of small, black specks.  Quartz seems to have a more than usual share in its composition, and we occasionally found crystals of that substance upon the shores.  The black specks were thought to be grains of tin, and to have communicated a deleterious quality to the water used by the shipwrecked people.  The exceptions to the general prevalence of granite were few:  they consisted of some black, and some grey slate, in thin strata, placed nearly perpendicular to the horizon; but even here, the granite had pervaded the fissures of the strata; and, in two instances, a substance which, from its appearance, I supposed to be a toad stone, had insinuated itself.