Page:A Voyage to Terra Australis Volume 1.djvu/411

Kanguroo Island.]

say, that it was the sole place found by us where the hope of procuring fresh water could be entertained.

Having received on board a good stock of wood, the launch was hoisted in, and every thing prepared for going to sea. Next morning, so soon as the sun was sufficiently elevated to be observed in the artificial horizon, I landed to take the last set of observations for the time keepers; after which the anchor was weighed, and we steered out of Nepean Bay with a light breeze from the south-west. Towards noon it fell calm, and finding by the land that the ship was set westward, an anchor was dropped nearly in our first place off Kanguroo Head; and Mr. Westall took the sketch given in the Atlas.

The rates of the time keepers were obtained, for the sake of expedition, from single altitudes of the sun's upper and lower limbs, taken from a quicksilver horizon with a sextant fixed on a stand; the time being noted from Arnold's watch, compared with Earnshaw's time keepers before going on shore and immediately after returning. From the altitudes of the 3rd, 4th, and 6th, in the morning, the rates of the two time keepers and their errors from mean Greenwich time, reduced to noon there on the last day, were as under:

In deducing these errors, the longitude given by the time keepers on our first arrival from Spencer's Gulph, which I consider to be equally good with that of Port Lincoln, was used, with a correction of —1′ 20″ for the change of place. The medium of the Port-Lincoln rates was something greater than that now found; which corresponded with the time keepers having given the longitude of Kanguroo Head less on the second than on the first arrival. This was some proof that the letting down had not affected the rates, and tended to give me confidence in their accuracy.