These shells are found both in the American and Indian seas.
The principal pearl fisheries are off the coasts of Hindostan and Ceylon. The fishing usually commences about the month of March, and occupies many boats and a great number of hands. Each boat has generally twenty-one men, of whom one is the captain, who acts as pilot; ten row and assist the divers, and the remainder are divers. The latter go down into the sea alternately by five at a time. To accelerate their descent they have a perforated stone of eighteen or twenty pounds weight, fastened by a cord to their great toe, or to some other part of their body. The depth of water through which they pass is from four to ten fathoms; and they collect the muscles into a bag of net-work which they hang about their necks. When desirous of ascending, they pull a rope as a signal to their companions in the boat to draw them up. They are often known to descend as many as forty or fifty times in a day, and at each plunge to return with more than a hundred shells. The usual time for the divers to remain under water does not much exceed two minutes, though some are able to continue immersed more than five minutes.
When the muscles are taken out of the boats, they are placed in heaps on the shore, where they continue about ten days, till the animals become quite putrid. They are then opened and searched for the pearls. One muscle sometimes contains many pearls, a hundred and upwards, large and small; and sometimes a hundred muscles have been opened without yielding a single pearl large enough to be of any value.
The pearls are sorted according to their size, by being passed through large brass sieves, or through saucers with round holes in the bottom. After having been sorted, they are drilled; and then washed in salt water to prevent any stains which might be left by the drilling. The arranging of them on strings is considered the most difficult task of a pearl merchant, in consequence of the correctness of judgment which is requisite in classing them according to their value.
The value of pearls is estimated by their size, roundness, colour and brightness. A handsome necklace of pearls, smaller than large peas, is worth from 170l. to 300l. whilst one of pearls not larger than pepper-corns may not be worth more than 20l. The King of Persia has a pear-shaped pearl so large and pure as to have been valued at 110,000l. sterling. The largest round pearl that has been known belonged to the Great Mogul, and was about two-thirds of an inch in diameter. Pearls from the fishery of Ceylon are considered more valuable in England than those from any other part of the world. The smaller kinds are called seed or dust pearls, and are of comparatively small value, being sold by the ounce to be converted into powder.
Nacre or mother-of-pearl is the inner part of the shell of the pearl muscle. This is of a brilliant and beautifully white colour, and is usually separated from the external part by aqua-fortis, or the lapidary's mill. Pearl muscle shells are on this account an important article of traffic to China and many parts of India, as well as to the different countries of Europe. They are manufactured into beads, snuff-boxes, buttons, and spoons, fish and counters, for card-players, and innumerable other articles.
The pearl muscles are not considered good as food; though, after having been dried in the sun, they are sometimes eaten by the lower classes of people in the countries near which they are found.
274. The COMMON or EDIBLE MUSCLE (Mytilus edulis, Fig. 79) is a testaceous animal, with a smooth double or bivalve shell of oblong oval form, pointed, and slightly keel-shaped at the beak, flatted and somewhat curved on one side.
The colour is generally blackish, and the length about three inches.
This species of muscle is found adhering to sub-marine rocks by certain silky threads, which it forms from its own body; and it is common both in the Indian and European seas.