The oysters are found in well-known and permanently located banks or paars in the upper end of the Gulf of Manaar, in the wide shallow plateau off the northwest end of the island and directly south of Adams Bridge. The hard calcrete bottom is formed mostly of sand combined with organic remains in a compact mass and with more or less coral and shell deposits. The density of the water, as determined by Professor Herdman (to whose important and valuable report[133] we are indebted for much information), is fairly constant at 1.023, and the temperature has a normal range of from 82° to 86° F. during the greater part of the year. The charts and records refer to about twenty paars, but most of these have never yielded extensively, either to the English or to the Dutch. In the aggregate, they cover an area fifty miles in length and twenty miles in width. Most of them are from five to twenty miles from the shore, and at a depth of five to ten fathoms. The principal paars are Cheval, Madaragam, Periya, Muttuvaratu, Karativu, Vankalai, Chilaw, and Condatchy. Only three have afforded profitable fisheries in recent years, _i. e._: Cheval, Madaragam and Muttuvaratu. The other paars are of practically no economic value at the present time. They become populated with tens of millions of oysters, which mysteriously disappear before they are old enough for gathering. Especially is this true of the Periya paar, which is about fifteen miles from the shore, and runs eleven miles north and south, varying from one to two miles in width. Frequently this is found covered with young oysters, which almost invariably disappear before the next inspection, owing, probably, to their being covered by the shifting bottom caused by the southwest monsoon. The natives call this the “Mother paar,” under the impression that these oysters migrate to the other paars. The Ceylon government has given very careful attention to all matters affecting the prosperity of the pearl resources. It has maintained a “Pearl Fishery Establishment,” consisting of a superintendent, an inspector and numerous divers, attendants, and sailors. The inspector examines the paars, determines when and to what extent they should be fished, and directs the operations. The superintendent conducts the work on shore, divides and sells the oysters, etc. The expense of this establishment has approximated $40,000 per annum when there has been a fishery, and about $22,500 without fishery expenses.