Page:A Voyage to Terra Australis Volume 1.djvu/375

Port Lincoln.]

eclipse, as recalculated by Mr. Crosley from Delambre's solar tables of 1806, and the new lunar tables of Burckhardt of 1812, differs but very little from them: it is 135° 46′ 8″ east.

The rates of the time keepers, deduced from equal altitudes on, and between Feb. 27 and March 4, and their errors from mean Greenwich time, at noon there on the last day of observation, were found to be as under:

Arnold's No. 176 altered its rate prodigiously on March 1st, and on the 2nd it stopped. His watch, No. 1736, varied in its rate from 7″,81 to 1″,90, so that it continued to be used only as an assistant.

The longitude given by the time keepers with the King-George's-Sound rates, on Feb. 27, the first day of observation at the tents, was by

But by allowing a rate accelerating in arithmetic progression, from those at King George's Sound to what were obtained at this place, the mean longitude by the two first time keepers would be 135° 52′ 16″, or 7′ 25″ to the east of the lunar observations; which quantity, if the positions of the Sound and of Port Lincoln be correct, is the accumulation of their irregularity during fifty-seven days. In laying down the coasts and islands from the Sound up to Cape Wiles, the longitudes are taken from the time keepers according to the accelerated rates, corrected by an equal proportion of the error 7′ 25″ in fifty-seven days. From Cape Wiles to the head of Port Lincoln the survey is made from theodolite bearings and observed latitudes, without the aid of the time keepers.