Page:The New International Encyclopædia 1st ed. v. 17.djvu/553

* SALT. 495 SALT. first, and salt, which is very soluble, being de- jKisited last. The drying up of lakes or the eaiH)ration of sea water in inclosed bays has thus led tu the formation of roek salt deposits. These deposits are frequently interstratificd with beds of sliale, wlueh it is sup|iosed were laid down durini; periods of high water when the streams washed an unusual quantity of sediment into the lake or bay. DiSTRiBiTiox AND Phoduction. Tile occur- rence of salt is widespread botli as regards its geographical and geological distribution. In the United States the most productive deposits are found in New York, Pennsylvania, Virginia, West Virginia, Ohio, ilichigan. Illinois, Kansas, Louisiana, and Texas. Important quantities of salt are won also from the waters of Great Salt Lake in Utah and from those of San Fran- cisco Bay in California. In Xcw York the salt is obtained from beds of the Salina series, where it exists as K-ns-shaped deposits of rock salt which attain an extreme thickness of 250 feet. Since the beds outcrop in the central part of the State and dip soutliward, some of the more southern deposits lie at a depth of 2700 feet. The Salina formation also carries salt in Michi- gan at a depth of from 1000 to 2200 feet. The great source of salt in this State, liowever. as ell as in Ohio, is the Lower Carboniferous, from which the brines sometimes have an added value owing to the presence of bromine. In A'est Vir- ginia the salt occurs in the Lower Carboniferous along the Kanawlia and Ohio rivers. Kansas has recently attained importance as a producer of both brine and rock salt, which is extracted from beds that lie along the contact of the Per- mian and Triassic systems at a depth of from 450 to 1000 feet. The extensive deposits occur- ring on Avery Island and the island of Petit Anse. La., are of recent geologic age. The production of salt in the United States has increased verv rapidlv. The output in 1881 was 0.200,000 barrels (of 280 pounds), valued at $4,200,000; in 1891 it was 9,987.945 barrels, valued at .^,716,121; and in 1901 it amounted to 20,500,721 barrels, valued at .$0,017,449. A considerable portion of the output in recent years has been converted into the various soda products. The production by States in 1901 was as follows: Production op Salt in the United States in 1901 New York Michigan Kansas Oliio California rtal! West Virginia.. Other States.... Total. Barrels Value 7,286.320 $2,089,834 7.729,641 2,437,677 2.087,791 614.365 1,153.535 455,924 (101,6.59 133.656 334,484 326.016 231.722 94,732 l,141,fJ69 465,245 20,.5f,6,721 $6,617,449 In Europe the most notable deposits of salt are found in the Cheshire district of England : at Stassfurt. Brunswick, and Hanover, CTermany: Wieliczka. Bochnia, and Hallstadt, .Austria: 'Milramaros. Hun.cary; the Crimea and the Donetz basin. Russia : and Cardona. Spain. The mines of Wieliczka. near Cracow, are famous for their great antiquity and the unusual size of the un- derground workings. France and Italy are ex- tensive producers of salt from sea water. The production of salt by the principal coun- tries of the world in 1900 was as follows: World's Pkoocction of Salt in 1900 •Short t(>n« rnlted States 2.9-'l,7S United Kingdom 2ioh4!701» Canada «2,065 lierinany 1,74»,386 France 1.199.(i75 .U8tila-Haiigary 572.042 ItUKsia (1899) 1.862,861 Itul.v 404,715 •Spain 49,',,»65 India 1.120.011 Japan (1899) 060,814 Other countries 81.717 Total 12,201,877 E.XTRAcriox JIethods. The simplest method of obtaining salt is by the evaporation of sea water, but tliis is seldom practiced except in those countries which have no supplies of sub- terranean brines or rock salt. It consists in conducting sea water into shallow tanks or pools and then evaporating the water by the sun's heat. After the gjpsum has crvstallized out the con- centrated brine is pumped into another vat where the salt eva])orates. Subterranean brines are extracted bv driving wells through which they are then pumped to the surface. Brine salt is also obtained from rock .salt deposits by a proc- ess of solution. In this ea.se a well is bored down to the salt stratum in the same manner as one bored for petroleum (q,v,). After the drill- ing has been completed, it is customary to case the well with a pipe. Inside of tliis there is put a second tubing, which usually extends to a lower depth than the outer pipe. The water is forced down between the outer and inner tub- ing, dissolves out the salt, and comes up through the inner tube. In some cases several wells are bored, the water being forced down one and the brine up the other. On reaching the surface it is discharged into settling tanks, in order to allow the suspended cla.v to settle. The brine is then pumped to the evaporating vats, which are either tanks with movable roofs, so that the salt can be eva]Hirated by solar heat, or else are placed over furnaces, or hot pipes, and the water evaporated b.v artificial heat. The latter is the prevalent method. In the solar process the brine is pumped into a series of tanks', in the first of which after standing for a while it becomes yellowish, due to the escape of carbonic acid gas and the pre- cipitation of the iron. In the next series of tanks the gj'psum separates, and these are known as the lime tanks. The brine remains here until the salt crystals begin to separate, indicating that the point of saturation is being approached. The brine or pickle is now drawn over into a third .series of tanks, in which the salt forms on the bottom, and is removed by means of rakes several times during the season. The solar process is chiefl.v adapted to the manu- facture of the coarser grades of salt. The finer .grades, such as table salt, are produced bv the u.se of artificial heat in the evaporation of the brine. This is carried on either in iron tanks or kettles. A tank is about 20 to 24 feet wide. 100 feet lon.s, and 12 inches deep. The tanks rest on brick arches and the heat is supplied from grates set at one end of the tank and some- what underneath it. Two pans are usually operated in connection with each other, known