In fixing the positions of places along the East Coast, I have made use of the time keepers from Port Jackson to Port Curtis, without any correction.  From Port Curtis to Broad Sound, the coast and islands are laid down from theodolite bearings taken on shore, combined with the observed latitudes; and consequently the accuracy in longitude of the first portion depends upon that of Port Jackson and the time keepers, and of the last, upon Upper Head and the survey.  These two unconnected longitudes meet at Port Curtis, and the difference between them is there no more than 5”.

From observations with the theodolite upon the top of Upper Head, the variation was 8 deg. 37’ east; but on moving the instrument ten yards to the south-west, it was 45’ less.  At two other stations on the west side of the sound, it was 8 deg. 15’, and 8 deg. 0’; and on board the ship 7 deg. 17’ and 7 deg. 46’, corrected.  On the east side of the sound it differed at six stations on shore, from 8 deg. to 6 deg.; and on board the ship was 6 deg. 44’ corrected.  As general results, therefore, but subject to many small deviations, the variation may be taken,

On the west side of Broad Sound at 8 deg. 0’ E.
On the east side 7 0
At the head of the sound it was,
at one station 12 deg., at another 10 deg.;
the mean, 11 0

The differences between the two sides of the sound, both on shore and on board, are nearly similar to what took place in Shoal-water Bay.

The rise of tide and time of high water have been mentioned; but it may be proper to say what I conceive to be the cause of the extraordinary rise in Broad Sound.  From Cape Howe, at the southern extremity of the East Coast, to Port Curtis at the edge of the tropic, the time of high water falls between seven and nine hours after the moon’s passage, and the rise does not exceed nine feet; but from thence to the northward, commencing with Keppel Bay, the time becomes later, and the rise augments, till, at Broad Sound, they reach eleven hours, and between thirty and thirty-five feet.  The principal flood tide upon the coast is supposed to come from the south-east, and the ebb from the north, or north-west; but from the particular formation of Keppel and Shoal-water Bays, and of Broad Sound, whose entrances face the north, or north-west, this ebb tide sets into them, and accumulates the water for some time, becoming to them a flood.  This will, in some degree, account for the later time and greater rise of the tide; and is conformable to what captain Cook says upon the same subject (Hawkesworth, III. 244); but I think there is still a super-adding cause.  At the distance of about thirty leagues to the N. N. W. from Break-sea Spit, commences a vast mass of reefs, which lie from twenty to thirty leagues from the coast, and extend past Broad Sound.  These reefs, being mostly dry at low water, will impede the free access of the tide;