and in the giant clam (Tridacna). Pearls are sometimes formed in univalve shells; thus pink pearls have been taken from the giant conch-shell (Strombus gigas) of the West Indies, as well as from certain species of Turbinella.
Pearl Fisheries. The average annual value of the pearl fishery of Northern Australia is $296,000, the industry having been founded at Thursday Island. It appears that the profits of the fishery are made out of the pearl shell only, because so many pearls, and often very valuable ones, are stolen by divers. Saville Kent distinguishes two species of pearl shells; viz. the large white shell (Meleagrina margaritifera) and a smaller black-edged form which he names Meleagrina nigro-marginata. Kent has proved that it is possible to transplant living pearl oysters. Under favorable conditions the shell is supposed to attain in three years the marketable size of eight or nine inches in diameter, while in five years a pair of shells may weigh five or six pounds, the extreme weight being ten pounds. The centre for labor and supplies of the Queensland fishery is Singapore, this port being an excellent market for the shells, while more pearls probably change hands here than in any other place in the world, large quantities being purchased for the Chinese market, where there is an extensive demand for second-class pearls.
The pearl oysters live at depths of from eight to twenty or more fathoms. For collecting the oysters small vessels of from 12 to 15 tons are most convenient. Two or more such boats are usually accompanied by a larger vessel as a storeship. The best divers are Japanese; Filipinos are also good, and Malays are employed. The diver takes with him a netted bag made of rope. When the depth is from eight to fifteen fathoms the diver can work at the bottom for two or more hours, but at a greater depth he cannot remain on the bottom more than fifteen minutes. The shells usually live in strong currents and in narrow channels between groups of islands, where they lie on a hard bottom.
The pearl fishery of the Mississippi and its tributaries is of much greater importance than is generally known. During recent years a thousand persons have been engaged in this industry on the Mississippi River alone. In 1901 a single firm is stated to have bought from these fishermen $100,000 worth of pearls, besides the clam or mussel shells from which pearl buttons are made. It is said that the supply of pearls is not being exhausted, but that the demand has increased so rapidly in the last fifteen years as to treble prices. The centre of the industry is Muscatine, Iowa.
In the United States the fresh-water pearl industry dates back to 1857, when the ‘Queen Pearl’ was found in New Jersey. It was sold to the Empress Eugenie for $2500 and is said to be worth now four times that sum. Tennessee, Kentucky, and Wisconsin are the leading States in the pearl industry, and in the ten years succeeding 1889 it is said that more than $25,000 worth of pearls were collected in Wisconsin alone. So great has been the destruction of the mussels there that in many places they are nearly if not quite exterminated.
PEARL. A beautiful English poem belonging to the second half of the fourteenth century. It is a lament of a father for a lost child, symbolized by a pearl. The poet possessed a spotless pearl. One day as he was in an arbor it slipped from his hand down through the grass and the flowers into the earth. Wandering afterwards into the arbor in search of the lost gem, he fell asleep amid the flowers, and in vision saw his lost child by the shimmering cliffs of the new Jerusalem. The poem consists of 101 twelve-line stanzas. The dialect is West-Midland. That the poet lived in the West of England near the Welsh borders is all that is known of him. Consult Pearl, edited, with a modern English version, by Israel Gollancz (London, 1891).
PEARL ASH (so called on account of the color), or Potashes. Crude potassium carbonate obtained from wood ashes. The commercial product is made in Canada, as follows: Wood is burned in pits and the resulting ash spread on a stone floor, sprinkled with water, and worked till it is damp, frequently with the addition of a little lime. The damp ash is then placed in casks containing false bottoms, covered with straw and hot water poured over them. The liquid, which is drawn off from a plug hole at the bottom, is boiled down, and finds some use in this condition as a manure owing to the soluble potash that it contains. The crude pearl ash thus obtained may be purified by heating and then cooled, during which the sulphate and chloride, together with the insoluble matter, are separated out, while the clear supernatant liquid is drawn off and boiled down until it crystallizes. When sufficiently pure this product finds use in the manufacture of flint glass. Ordinary pearl ash is used principally, however, in the manufacture of soap.
PEARL HARBOR. An inlet on the south coast of Oahu, Hawaii, six miles west of Honolulu (Map: Hawaii, C 2). It consists of several land-locked basins with a narrow entrance inside of which there is a depth of 60 feet. Outside, however, a coral reef prevents the entrance of large vessels. In 1884 the United States obtained the right from the Hawaiian Government to establish here a coaling and repair station, and several surveys were made by the United States Government. The harbor, however, was not utilized, and the acquisition of the harbor of Honolulu in 1898 rendered its improvement unnecessary.
PEARLITE (so called on account of the pearly lustre). A glassy or once glassy rock which exhibits a ready separation by cracks into spherical or spheroidal forms. These so-called pearlitic cracks may arise from stresses set up during the cooling of the magma, or from differential expansion and contraction about spherulitic masses of feldspar.
PEARL MILLET. A cereal grain. See Guinea Corn.
PEARL OYSTER. A tropical bivalve (Meleagrina margaritifera) noted for producing precious pearls and mother-of-pearl. See Pearl.
PEARL RIVER. A river of Mississippi. It rises in Winston County in the east central part of the State, and flows southward, emptying into the Mississippi Sound after having formed for some distance the boundary between Mississippi and Louisiana (Map: Mississippi, F 8). It is about 300 miles long, but its navigation is impeded by shoals and sand bars.
- Vol. XV.—32.
