But we were detained until the 5th of October before the tide rose high enough to float the cutter.
During the time that the carpenter was thus occupied all the crew were employed either in assisting him or in cutting wood and filling water; so that I had no opportunity either of visiting the surrounding islands or of examining the country in the vicinity of the bay: but when the repairs were completed and the people were more at leisure I made an excursion as far as Bat Island, off Cape Brewster.
From the summit of this island a set of bearings was obtained, particularly of the islands to the northward and westward. The ascent, on account of its steep and rugged nature, was very difficult and even dangerous, for the stones were so loose and decomposed that no solid footing could be found. The top of the rock is covered with a thick brush of Acacia leucophoea (of Lacrosse Island) many trees of which were obliged to be cut down or cleared away before the various objects could be seen from the theodolite. Mr. Cunningham collected here specimens of eighteen different sorts of plants.
Bat Island is a mass of sandstone superincumbent upon a quartzose basis and intersected by nearly vertical veins of white quartz, the surface of which was in a crystallized state. The floor of the cavern was covered with heaps of water-worn fragments of quartzose rock, containing copper pyrites, in some of which the cavities were covered by a deposit of greenish calcedony. The sides of the cavern had a stalagmitical appearance but the recess was so dark that we could not ascertain either its formation or extent; it did not however appear to be more than twelve or fourteen yards deep. On first entering it we were nearly overpowered by a strong sulphureous smell which was soon accounted for by the flight of an incredible number of small bats which were roosting in the bottom of the cave and had been disturbed by our approach. We attempted to grope our way to the bottom, but, not having a light, were soon obliged to give up its further examination.
The island is connected to the cape by a narrow ridge of rocks which the spring-tides may probably cover. The main corresponds with the island in character and general conformation, being extremely barren and rocky, and of the same description of sandstone, the strata of which appear nearly horizontal; the greatest deviation from that position not being more than an inclination of 5 degrees to the south-east.
Upon our return we landed at Caper Point near the bottom of the bay; where, on taking some bearings, a considerable local magnetic attraction was detected, for the needle of the theodolite was nearly eight degrees in error. Whilst I was thus employed Mr. Cunningham, who was my companion upon this excursion, ranged about among the shrubs in the vicinity and was fortunate in finding the fruit of a tree that was first seen by us at Cambridge Gulf, and had for some time puzzled us from its immense size and peculiar appearance. It proved to be a tree of the natural order Capparides, and was thought to be a capparis; the gouty habit of the stem, which was soft and spongy, gave it an appearance of disease: but as all the specimens, from the youngest plant to the full-grown tree, possessed the same deformed appearance, it was evidently the peculiarity of its habit. The stem of the largest of these trees measured twenty-nine feet in girth whilst its height did not exceed twenty-five feet. "It was at this time in the earliest stages of foliation, the extremities of the naked branches appearing green; and one bud that was opened exhibited the character of Folium quinatum."* One of these trees has been introduced in the view of the encampment at Careening Bay. It bore some resemblance to the adansonia figured in the account of Captain Tuckey's expedition to the Congo.
(*Footnote. Cunningham manuscripts.)
The only quadruped that was seen upon this excursion was a small opossum which appeared to be the same animal that the colonists at Port Jackson call the native cat: its colour was light red with small white spots.
The principal object of my investigation was to find an opening in the bottom of the bay communicating with a large sheet of water that we had seen from the hills to the southward; but as we were not successful in finding any it was supposed that its communication with the sea must be to the westward of Cape Brewster. Mr. Hunter and Mr. Cunningham had previously made an excursion in that direction to the summit of a hill, named by the latter gentleman after Thomas Andrew Knight, Esquire, the President of the Horticultural Society. From this elevation they had a good view of the water which appeared to be either a strait or an inlet of considerable size; it was subsequently called Rothsay Water. The country between it and our encampment was very rocky and rugged; but although almost destitute of soil it was sprinkled with some dwarf timber of various descriptions; and, had it not been for the late fires, there would have been a good share of grass.
The fires were still burning; and while we were employed upon the vessel the little grass that had before escaped the flames was consumed before our eyes, which greatly increased the oppressive heat we were experiencing. The thermometer during the day, exposed to a current of air and shaded from the sun, generally indicated a temperature of between 94 and 98 degrees; and on one occasion although it was exposed to a fresh sea-breeze the mercury stood at 101 degrees at noon: at night however we were usually relieved by its falling to 75 degrees; and at two o'clock in the morning it generally stood at 73 degrees. The maximum and minimum temperature during fourteen days was 101 degrees and 72 1/2 degrees. The daily range of the thermometer was as much as 20 degrees, while the mercury on board did not rise or fall more than 3 or 4 degrees. This great difference is to be attributed to the cooling power of the dew which was precipitated most copiously every night upon the surface of the earth; whilst the water, not being so easily affected by this nightly radiation, took so much longer to cool. In the daytime the reverse took place; for the earth being much more heated by the action of the sun's rays than the water, the temperature on shore was much greater than on the sea.