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.
Earnshaw's No. 543, fast 0h 0' 18.03" and losing 8.46" per day.
No. 520, slow 0 45 29.66 and losing 18.07" per day.
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 Kangaroo 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.
The variation observed on shore, with the theodolite, was 5° 48' east.
Do. with azimuth compass, No. 1 with the theodolite, was 2° 58' east.
For this difference between the instruments, I find it difficult to account satisfactorily; but it is the same way, and nearly similar in quantity to what was observed in Lucky Bay. The true variation on board the ship, deduced from azimuths taken at anchor two miles to the north-east, and using the compasses No. 1 and 2, was as before mentioned, 4° 13', nearly the mean of the above; but the bearings taken with the theodolite at Kangaroo Head and Prospect Hill showed only 2½° east, as compared with the bearings on board the ship. There can be little doubt of the existence of magnetic substances in the lands about here, more particularly, as I think, in Yorke's Peninsula; and there will presently be occasion to notice more instances of their effect.
The approach of the winter season, and an apprehension that the discovery of the remaining unknown part of the South Coast might not be completed before a want of provisions would make it necessary to run for Port Jackson, prevented me from stopping a day longer at Kangaroo Island than was necessary to obtaining rates for the time-keepers, and consequently from examining the south and west parts of that island. The direction of the main coast and the inlets it might form were the most important points to be now ascertained; and the details of particular parts, which it would interfere too much with those objects to examine, were best referred to the second visit, directed by my instructions to be made to this coast. When, therefore, the rising of a breeze made it advisable to get under way from Kangaroo Head, which was not until two in the afternoon, we proceeded for the eastern outlet of the Investigator's Strait, in order to prosecute the discovery beyond Cape Jervis.
The wind was at south-east; and the tide being against us, but little progress was made until the evening, when it became favourable. Our soundings were irregular, and some rocky islets being seen without side of the opening, I stood in at nine o'clock, to look for anchorage at the east end of Kangaroo Island; and finding no shelter there, we ran a little to leeward into a small bay which I had observed before dark, and anchored at half past ten, in 4½ fathoms, on a bottom of hard sand. At daylight [WEDNESDAY 7 APRIL 1802], the following bearings were taken.
East point of the little bay, dist. 1½ mile, East.
West point, distant three miles, N. 38° W.
Cape Jervis, inner low point, N. 3 W.
Eastern extreme of the coast, N. 65 E.
The bay is perfectly sheltered from all southern winds; and as there were several spots clear of wood near the beach, it is probable that the kangaroos, and perhaps cassowaries, might be numerous. We did not stop to land, but got under way so soon as the bearings were taken, to beat out of the strait against the south-east wind; so little was gained, however, after working all the day, that at eight in the evening the ship was still off the east end of Kangaroo Island.
This part of the Investigator's Strait is not more, in the narrowest part, than seven miles across. It forms a private entrance, as it were, to the two gulphs; and I named it Back-stairs Passage. The small bay where we had anchored is called the Ante-chamber; and the cape which forms the eastern head of the bay and of Kangaroo Island, and lies in 35° 48' south and 138° 13' east, received the appellation of Cape Willoughby. Without side of the passage, and almost equidistant from both shores, there are three small, rocky islets near together, called the Pages, whose situation is in latitude 35° 46½' and longitude 138° 21' east; these are the sole dangers in Back-stairs Passage, and two of them are conspicuous. Our soundings in beating through were from 8 to 23 fathoms; and in a strong rippling of tide like breakers there was from 10 to 12, upon a bottom of stones and shells.