Page:A Voyage to Terra Australis Volume 2.djvu/80

74

The mean is 7′ 14″ to the east of the lunars; but on using rates equally accelerated from those at Port Jackson to the above at Upper Head, and commencing the acceleration on Aug. 15, at Keppel Bay, where the time keepers were found to be keeping their former rates, the mean longitude will be 149° 48′ 56″,6, or 2′ 3″,6 from the lunar observations; which is therefore the presumable sum of their irregularities after August 15, or in 27,7 days.

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° 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° 15′, and 8° 0′; and on board the ship 7° 17′ and 7° 46′, corrected. On the east side of the sound it differed at six stations on shore, from 8° to 6°; and on board the ship was 6° 44′ corrected. As general results, therefore, but subject to many small deviations, the variation may be taken, 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;