Page:A Voyage to Terra Australis Volume 2.djvu/157

Wellesley's Islands.]

No. 520 therefore differed very little to the east of the lunar observations, and the first day's rate was almost exactly the same as that with which we had quitted Upper Head; whilst No. 543 differed greatly, both in longitude and rate. A similar discordance had been noticed at the Cumberland Island, marked l2, twenty days after leaving Upper Head; No. 520 then differed only 1′ 1″,2 from the survey, but No. 543 erred 7′ 2″,2 to the east. I have therefore been induced to prefer the longitude given by No. 520, to the mean of both time keepers; and accordingly, the positions of places before mentioned or laid down in the charts, between Upper Head and Sweers' Island, including Torres' Strait, are from this time keeper alone; with such small correction equally proportioned, as its error from the lunars, 2′ 50″,2 to the east in fifty-two days, made necessary.

No. 543 had undergone some revolution on the passage, but seemed at this time to be going steadily; whereas No. 520, which had kept its rate so well, now varied from 18″,79 to 25″,39, and ceased to be entitled to an equal degree of confidence. In bearings taken on the east side of Bentinck's Island, the variation appeared to be a full degree greater than on the west side of Sweers' Island.

The tides in the Investigator's Road ran N.N.E. and S.S.W., as the channel lies, and their greatest rate at the springs, was one mile and a quarter per hour; they ran with regularity, but there was only one flood and one ebb in the day. The principal part of the