SALTPETRE.
In the country of Kattaun, near the head of Urei River, there are extensive caves (goha) from the soil of which saltpetre (mesiyu mantah) is extracted. M. Whalfeldt, who was employed as a surveyor, visited them in March 1773. Into one he advanced seven hundred and fortythree feet, when his lights were extinguished by the damp vapour. Into a second he penetrated six hundred feet, when, after getting through a confined passage about three feet wide and five in height, an opening in the rock led to a spacious place forty feet high. The same caves were visited by Mr. Christopher Terry and Mr. Charles Miller. They are the habitation of innumerable birds, which are perceived to abound the more the farther you proceed. Their nests are formed about the upper parts of the cave, and it is thought to be their dung simply that forms the soil (in many places from four to six feet deep, and from fifteen to twenty broad) which affords the nitre. A cubic foot of this earth, measuring seven gallons, produced on boiling seven pounds fourteen ounces of saltpetre, and a second experiment gave a ninth part more. This I afterwards saw refined to a high degree of purity; but I conceive that its value would not repay the expense of the process.
BIRDS-NEST.
The edible birds-nest, so much celebrated as a peculiar luxury of the table, especially amongst the Chinese, is found in similar caves in different parts of the island, but chiefly near the sea-coast, and in the greatest abundance at its southern extremity. Four miles up the river Kroi there is one of considerable size. The birds are called layang-layang, and resemble the common swallow, or perhaps rather the martin. I had an opportunity of giving to the British Museum some of these nests with the eggs in them. They are distinguished into white and black, of which the first are by far the more scarce and valuable, being found in the proportion of one only to twenty-five. The white sort sells in China at the rate of a thousand to fifteen hundred dollars the pikul (according to the Batavian Transactions for nearly its weight in silver), the black is usually disposed of at Batavia at about twenty or thirty dollars for the same weight, where I understand it is chiefly converted into a kind of glue. The difference between the two sorts has by some been supposed to be owing to the mixture of the feathers of the birds with the viscous substance of which the nests are formed; and this they deduce from the experiment of steeping the black nests for a short time in hot water, when they are said to become white to a certain degree. Among the natives I have heard a few assert that they are the work of a different species of bird. It was also suggested to me that the white might probably be the recent nests of the season in which they were taken, and the black such as had been used for several years successively. This opinion appearing plausible, I was particular in my inquiries as to that point, and learned what seems much to corroborate it. When the natives prepare to take the nests they enter the cave with torches, and, forming ladders of bamboos notched according to the usual mode, they ascend and pull down the nests, which adhere in numbers together, from the sides and top of the rock. I was informed that the more regularly the cave is thus stripped the greater proportion of white nests they are sure to find, and that on this experience they often make a practice of beating down and destroying the old nests in larger quantities than they trouble themselves to carry away, in order that they may find white nests the next season in their room. The birds, I am assured, are seen, during the building time, in large flocks upon the beach, collecting in their beaks the foam thrown up by the surf, of which there appears little doubt of their constructing their gelatinous nests, after it has undergone, perhaps, some preparation from commixture with their saliva or other secretion in the beak or the craw; and that this is the received opinion of the natives appears from the bird being very commonly named layang-buhi, the foam-swallow. Linnaeus however has conjectured, and with much plausibility, that it is the animal substance frequently found on the beach which fishermen call blubber or jellies, and not the foam of the sea, that these birds collect; and it is proper to mention that, in a Description of these Nests by M. Hooyman, printed in Volume 3 of the Batavian Transactions, he is decidedly of opinion that the substance of them has nothing to do with the sea-foam but is elaborated from the food of the bird. Mr. John Crisp informed me that he had seen at Padang a common swallow's nest, built under the eaves of a house, which was composed partly of common mud and partly of the substance that constitutes the edible nests. The young birds themselves are said to be very delicate food, and not inferior in richness of flavour to the beccafico.
TRIPAN.
The swala, tripan, or sea-slug (holothurion), is likewise an article of trade to Batavia and China, being employed, as birds-nest or vermicelli, for enriching soups and stews, by a luxurious people. It sells at the former place for forty-five dollars per pikul, according to the degree of whiteness and other qualities.
WAX.
Beeswax is a commodity of great importance in all the eastern islands, from whence it is exported in large oblong cakes to China, Bengal, and other parts of the continent. No pains are taken with the bees, which are left to settle where they list (generally on the boughs of trees) and are never collected in hives. Their honey is much inferior to that of Europe, as might be expected from the nature of the vegetation.
GUM-LAC.
Gum-lac, called by the natives ampalu or ambalu, although found upon trees and adhering strongly to the branches, is known to be the work of insects, as wax is of the bee. It is procured in small quantities from the country inland of Bencoolen; but at Padang is a considerable article of trade. Foreign markets however are supplied from the countries of Siam and Camboja. It is chiefly valued in Sumatra for the animal part, found in the nidus of the insect, which is soluble in water, and yields a very fine purple dye, used for colouring their silks and other webs of domestic manufacture. Like the cochineal it would probably, with the addition of a solution of tin, become a good scarlet. I find in a Bisayan dictionary that this substance is employed by the people of the Philippine Islands for staining their teeth red. For an account of the lac insect see in the Philosophical Transactions Volume 71 page 374 a paper by Mr. James Kerr.