st Hill, the top, N. 16 deg. 40' W.
Northumberland Isles. the peak marked 'h', N. 25 15 E.
Long Island, extreme of the north point, N. 73 35 E.
Upper Head, on the west shore up Broad Sound, S. 39 55 E.

The 4th Flat Isle is about one mile long, and there is a smaller lying
off its south-east end; they are a little elevated, and bear grass and
small trees; but the shores are covered with mangroves, and surrounded
with extensive flats of mud and sand. The main coast, from which they lie
two or three miles, is also low, with mangroves and shelving mud banks;
but there is a deep channel between, of a mile in width. In the evening,
when the flood made, we steered into this channel with a light
sea-breeze; but not having time to clear it before dark, the anchor was
dropped in 4 fathoms at six o'clock.

My attention was attracted this evening by the vast extent of mud left
dry on each side of the channel, and I ordered particular attention to be
paid to the tides during the night. At eleven o'clock, when the flood had
ceased running, the depth was sounded and the lead line measured, and the
same at half past five in the morning [SATURDAY 11 SEPTEMBER 1802] when
it was low water; the difference was no less than thirty-two feet, and it
wanted a day of being full moon; so that the springs may reach two or
three feet higher. The flood set S. by E., but its greatest rate did not
exceed one mile and three quarters an hour.

At daylight the wind was south-east, directly against us. We backed and
filled, drifting up with the flood between the shoals on each side, and
having the Lady Nelson and a boat ahead; but on approaching the end of
the channel, our passage into the sound was blocked up by a bank running
across, upon which there was not water enough for the ship by a fathom,
and we therefore anchored. At nine the tide had risen a fathom. and we
passed over into the open sound; the depth immediately increasing to 4
and 7 fathoms, reduced to low water. So long as the flood continued
running we worked up the sound; and when it ceased, anchored three miles
from a shallow opening in the low western shore, the second which had
been observed. We again proceeded upwards with the evening's tide until
dusk; and at nine next morning [SUNDAY 12 SEPTEMBER 1802] passed a fifth
opening, and anchored abreast of the hilly projection on its east side,
which I have named _Upper Head_, in 4 fathoms, soft b