[NORTH COAST. TORRES' STRAIT.]
Until noon, we had no soundings with from 25 to 30 fathoms of line, but then found broken coral and shells at the latter depth; the great reefs to windward were two or three miles distant, stretching south-west, and our situation and bearings were as under:
Latitude observed, 9° 53½' S.
Longitude from time keeper, 143 42 E.
Murray's Isles, the largest, highest part, S. 88½ E.
Murray's Isles, the westernmost, highest part, S. 81½ E.
Darnley's I., highest part, obscure, N. 10 E.
A small, low isle, To the westward.
Nearest reef, distant two miles, S. 67° to N. 43 W.
Having a fresh breeze at S. E. by E, we ran at the rate of six knots, following the chain of reefs lying to windward. On the other side, there were still very few reefs; but several low isles were distinguished, similar to that seen at noon; these were small, but seemingly well covered with wood, and appertain, as I judge, to the group called by Mr. Bampton, Cornwallis' Range. At half past two, we passed between reefs one mile and a half asunder, having no ground at 25 fathoms; and then the chain which had been followed from Murray's Isles, either terminated or took a more southern direction. Another small, woody isle was then in sight, nearly in our track, at four it bore N. 67° W., two-and-half miles; and not seeing any other island ahead to afford shelter for the night, we bore away round the south end of its reef, and came to an anchor in 17 fathoms, coral sand.
Cent. of the island, dist. 1¼ miles, bore, S. 83° E.
The surrounding reef, N. 78° to S. 12 E.
A woody isle, westmost of five seen this p. m., N. 9 W.
A dry sand, set from the mast head, S. W.¾ S.
A boat was lowered down, and I went on shore with the botanical gentlemen, to look about the island. It is little better than a bank of sand, upon a basis of coral rock; yet it was covered with shrubs and trees so thickly, that in many places they were impenetrable. The north-western part is entirely sand, but there grew upon it numbers of pandanus trees, similar to those of the east coast of New South Wales; and around many of them was placed a circle of shells of the chama gigas, or gigantic cockle, the intention of which excited my curiosity.
It appeared that this little island was visited occasionally by the Indians, who obtained from it the fruit of the pandanus, and probably turtle, for the marks of them were seen; and the reef furnishes them with cockles, which are of a superior size here to those we had found upon the reefs of the East Coast. There being no water upon the island, they seem to have hit upon the following expedient to obtain it: Long slips of bark are tied round the smooth stems of the pandanus, and the loose ends are led into the shells of the cockle, placed underneath. By these slips, the rain which runs down the branches and stem of the tree, is conducted into the shells, and fills them at every considerable shower; and as each shell will contain two or three pints, forty or fifty thus placed under different trees will supply a good number of men. A pair of these cockle shells, bleached in the sun, weighed a hundred and one pounds; but still they were much inferior in size to some I have since seen.
The fruit of the pandanus, as it is used by these Indians and by the natives of Terra Australis, affords very little nourishment. They suck the bottom part of the drupes, or separated nuts, as we do the leaves of the artichoke; but the quantity of pulp thus obtained, is very small, and to my taste, too astringent to be agreeable. In the third volume of the Asiatic Researches, the fruit of the pandanus is described as furnishing, under the name of Mellori, an important article of food to the inhabitants of the Nicobar Islands; and in Mauritius, one of these species is planted for its long and fibrous leaves, of which sacks, mats, and bags for coffee and cotton are in a made.
This little island, or rather the surrounding reef, which is three or four miles long, affords shelter from the south-east winds; and being at a moderate day's run from Murray's Isles, it forms a convenient anchorage for the night to a ship passing through Torres' Strait: I named it Half-way Island. It is scarcely more than a mile in circumference, but appears to be increasing both in elevation and extent. At no very distant period of time, it was one of those banks produced by the washing up of sand and broken coral, of which most reefs afford instances, and those of Torres' Strait a great many. These banks are in different stages of progress: some, like this, are become islands, but not yet habitable; some are above high-water mark, but destitute of vegetation; whilst others are overflowed with every returning tide.
It seems to me, that when the animalcules which form the corals at the bottom of the ocean, cease to live, their structures adhere to each other, by virtue either of the glutinous remains within, or of some property in salt water; and the interstices being gradually filled up with sand and broken pieces of coral washed by the sea, which also adhere, a mass of rock is at length formed. Future races of these animalcules erect their habitations upon the rising bank, and die in their turn to increase, but principally to elevate, this monument of their wonderful labours. The care taken to work perpendicularly in the early stages, would mark a surprising instinct in these diminutive creatures. Their wall of coral, for the most part in situations where the winds are constant, being arrived at the surface, affords a shelter, to leeward of which their infant colonies may be safely sent forth; and to this their instinctive foresight it seems to be owing, that the windward side of a reef exposed to the open sea, is generally, if not always the highest part, and rises almost perpendicular, sometimes from the depth of 200, and perhaps many more fathoms. To be constantly covered with water, seems necessary to the existence of the animalcules, for they do not work, except in holes upon the reef, beyond low-water mark; but the coral sand and other broken remnants thrown up by the sea, adhere to the rock, and form a solid mass with it, as high as the common tides reach. That elevation surpassed, the future remnants, being rarely covered, lose their adhesive property; and remaining in a loose state, form what is usually called a key, upon the top of the reef. The new bank is not long in being visited by sea birds; salt plants take root upon it, and a soil begins to be formed; a cocoa nut, or the drupe of a pandanus is thrown on shore; land birds visit it and deposit the seeds of shrubs and trees; every high tide, and still more every gale, adds something to the bank; the form of an island is gradually assumed; and last of all comes man to take possession.