Page:A Voyage to Terra Australis Volume 2.djvu/185

Pellew's Group.]

change; but in No. 520, the rate is more than 8″ greater, and the longitude was getting 1½′ per day too much to the east, as well before as after it was let down. The coast from Sweers' to Observation Island is consequently laid down by No. 543, with the small accelerating correction arising from the 0″,19 increase of rate in 16,4 days. In the bearings taken at different parts within the group, the variation seemed to differ from 2° 30′ to 1° 30′. The largest variations were on the east sides of the islands, and the smallest on the west sides; seeming to show an attraction of the land upon the south end of the needle. On board the ship, when coasting along the east side of Vanderlin's Island, and the whole group lay to the west, the variation appeared from the bearings to be as much as 4° east.

The best observation made on the tide, was on the 23rd, during my boat excursion to the south end of Vanderlin's Island. On that morning the moon passed over the meridian at sixteen minutes past ten, and the perpendicular movements of the tide were as follows. At seven o'clock, when I left the shore, the tide was falling; on landing at nine it was stationary, and appeared to be low water; at noon it rose fast, and at three was still rising, and continued so to do, but slowly, until seven in the evening. The tide then began to fall; but after subsiding one foot, it rose again until ten o'clock, and had then attained its greatest height. Low water took place therefore about an hour before, and high water at eleven hours and a quarter after the moon passed the meridian: the rise appeared to be from four to seven feet. At Wellesley's Islands high water had taken place an hour and a half earlier, which seems extroardinary, if, as it necesarily must, the flood come from the northward. I think it very probable, that the tide in both places will follow what was observed in King George's Sound on the South Coast; where high water, after becoming gradually later