sulphur a hard crust forms, two inches thick. Digging is only carried on at morning and evening, the heat being too great at midday. Round holes are made, eight to nine feet apart, two feet deep, and with an outlet from above of one foot, and from below of three or four feet. Sulphur is also found in the solfatara of Gunong Prewa, but in trifling quantity. A great deal exists on the sides of Tambora.
Tripoli possesses a sulphur-deposit important both for extent and richness, but it is not worked.
In Turkey, native sulphur is found in some quantity adjacent to the lead lodes at Devrent (Derbend), near Alashehr, Salyklce, and Nymphi. A sulphur-mine exists two days' ride from Arta, and four from Butrinto, Albania, and there are other mines near the Dardanelles and at Alahtan, about six hours from Kassaba.
In the United States, sulphur is found native in Nevada, California, Utah, Virginia, Louisiana, and other States, and occurs in beds of considerable bulk in Uintah county, Wyoming, near Evanstown, where it is said to be quite pure; also in some quantity in the Yellowstone Park, Montana, and in various localities in New Mexico. It is only worked to any extent in Nevada and California, and even there not on a large scale, the total production in 1880 being stated at under six hundred tons. Locally produced sulphur can not compete in price with imported Sicilian, on account of the cost of land transport; it is, moreover, found to be often contaminated with arsenic, which greatly reduces its market value and limits its application. At the most important mine, called the Rabbit Hole, in Humboldt County, Nevada, the sulphur occurs as an impregnation in a white volcanic tuff or breccia, of Miocene age. The deposit is worked by regular mining, and the mineral, containing fifteen to forty per cent of sulphur, is dealt with by the steam process, the production being sometimes six tons a day. At the Pluton mines, California, the sulphur is found as a crystalline body scattered through a confused mass of decomposed rocks, and intimately associated with cinnabar, apparently occupying an ancient crater. The mineral is removed altogether, and the sulphur is either recovered by steam process, or, if both sulphur and cinnabar are in paying quantities, the mass is put into a mercury distilling furnace, and the sulphur is separated from the mercury by passing superheated steam into a chamber situated in front of the mercury-condensing chamber.
Sulphur is extracted from the earthy materials with which it is intimately associated in nature, by the following several means: 1. Dry heat (roasting the ore in mass); 2. Wet heat (melting out by the aid of aqueous solutions of salts, the salts being added to heighten the boiling-point); 3. Superheated steam; 4. Chemical solvents. The great bulk of all the sulphur produced is extracted by apparatus belonging to the first class, and including the calcarelle, calcarone, and doppione.
