The trepang exported from this section requires considerable care in preparation. After being gathered from the rocks they are cleaned, boiled, and partly dried in the air; then they are smoked with mangrove wood until dry and hard. The best class of trepang is packed in tin cases to keep it perfectly dry, as moisture ruins it. The product is marketed chiefly at Hongkong, where it is used in making the gelatinous soups for which the Chinese are so famous. The pearl-shell fisheries yield products of considerable value. The average depth from which the mother-of-pearl shell is gathered is seven or eight fathoms. Twenty fathoms represents the greatest depth in which divers, even in their diving suits, can work, so great is the pressure of the water upon them. The fishery is carried on chiefly for securing the shells, the finding of pearls being of secondary importance, since only about one shell in a thousand contains a pearl of much value. The shells themselves bring in the market from three hundred to eight hundred dollars per ton according to quality and size, and are used chiefly for making buttons and small ornaments. The Cairn Cross Islands, a little coral group midway between Cape Grenville and Cape York, are especially interesting as the home and nesting-place of the Torres Strait pigeons. These large white pigeons are highly esteemed for the table. They gather at the islands during the month of October and remain until the end of March. The nests are usually built in the forked branches of the mangrove trees that form extensive thickets along the coast. Each nest contains two white eggs. The Australian jungle-fowl or scrub-hen also frequents these islands as well as the mainland. The nests of these birds are large and unique. They consist of huge mounds of dead leaves, grass, sticks, and soft earth piled together by the adult birds in shaded and sequestered places. The mounds are about twenty feet in diameter and from ten to fifteen feet high. Several pairs of birds generally unite in their construction. When the mounds are completed the birds burrow holes in the centre and deposit their eggs, which are left to be hatched by the moist heat engendered by the decaying vegetation. Forty or fifty brick-red colored eggs as large as those of a turkey are sometimes found in a single nest. Both the eggs and the parent birds are excellent eating. The Australian bee-eater, a bird of attractive plumage, is found all over the northern islets of the Barrier Reef. It has a long, sharp curved bill and two long, narrow feathers in its tail. Its beautiful green plumage, varied with rich brown and black, and vivid blue on the throat, makes it an attractive bird.