ome parts of the southern land, between the extremes of S. 20 deg. 20' E.
and S. 59 deg. 35' W. At these different stations, the needle of the
theodolite was sometimes found to vary one or two degrees from itself, as
it had done at Preservation Island; an effect which I attribute to the
attraction of the rocks, having since experienced the same, and even
greater, differences in most places where the rocks, as here, are
granitic.

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