coarser qualities of salt are mostly made from sea-water or from brineS by a natural process of evaporation, although they consist sometimes of rock-salt ground to a suitable size. Along the shores of the Mediterranean the evaporation i3 effected by exposing the sea-water in shallow basins to the influence of sun and air. In Russia, Sweden, and other northern countries, salt is obtained by freezing sea-water in large reservoirs. As the ice so formed is nearly pure, repeated congelations leave the mother liquor more and more impregnated with salt, and the residuum is finally boiled down. 111 New York, Kansas, Michigan, Ohio; and West Virginia there are many manufactories of coars3 salt from the natural brines. By mere exposure in a series of shallow wooden vats, protected from the rain by movable covers, the liquid is first freed from its principal impurities. and then evaporated by solar heat—the coarse salt so °lib ined being largely used in the preservation of meat and fish. The most important of these establishments is at Onondaga. N. Y., where the finer grades of salt are also made. These finer qualities of salt, often known as boiled salt, result from the application of artificial heat to the brines. In many cases, however, and especially when the brines are weak and diluted. they are submitted to a preliminary process-of evaporation in the air, which not only concentrates the liquid, hut frees it from the carbonic acid and the ferrous earhonates with which it is frequently impregnated. This may be done in the wooden vats already mentioned, though a favorite process. superseding al; others iu Europe. consists in pumping the liquor up to a high reservoir and thence allowing it to trickle down through bundles of thorn or brush built up in the form of Si wall, the great amount of surface thus exposed to the wind and sun causing very rapid evaporation. This preliminary process is called "graduation." After the liquor has been sufficiently concentrated the separation of the salt is effected by artificial heat. This may be done in various ways. the most usual being those known as the kettle, the pan. and the steam processes. The first is peculiar to the United States, and is practiced especially m the Onondaga factories. Sonte 50 or 60 hemispherical iron kettles, capable of holding from 120 to 150 gals., are placed in a double row along a common flue, heated by fire-places at (will end. At the bottom of each of these kettles a pan with a long handle is intro dueed. upon Ivhieh are collected the impurities precipitated during the process of con cow ration. From time to thne the pan is r^moved and cleaned until the salt crystals begin to appear, when it is not replaced. After the salt has separated it is washed In the remainimg pickle. hung in baskets over the kettles. where it is drained for a few hours and then emptied into the store-rooms. Here it remains for a couple of weeks— a law in New York state makes a two weeks' drying in the store-room obligatory—and is then ready for the market.. The pan process. not often practiced in this country, is a favorite in England. The brine. after it has been " gradmited" to a sufficient specific gra vity. ix placed in largct shallow iron pans called the " forehenters," where it is boiled until the impurities have been deposited, and then when it has almost reached the Kitt,n ration point is run off into similar pans and to dryness, in the steam pro cess the graduated brine is placed in wooden vats called settlers, about 800 ft. long, 8 ft. wide, and 6 ft. deep, heated by means of a number of 4 in. steam pipes passing through them from end to cud. '1'lle impurities having been deposited in tne settlers, the liquid is drawn into other vats called "grainers," of the same length and width, but only a foot or two in depth. The salt forms very rapidly, and is lifted, drained, and stored in the sante way as in the kettle process. The•steam process is used in various places in the United States, particularly in the Saginaw valley in Michigan, where the kettle process is also practiced. Tne fineness of the salt in all cases depends upon the rapidity with 'which the evaporation is conducted, the most rapid boiling producing- the finest grained salt. The United States is remarkable for the number of its salt manufactories; no less than 23 of the states are or have been actively engaged in the production of the various grades of salt. Of these New York and Michigan are the chief. The former state has produced as much as 9,053,874 bush. in a single year (1862), but since that time the yield has declined and does not now average 800,000 bush. a year. The saline springs are principally in Onondaga county, in the towns of Syracuse, Salina, and Geddes. They are the property of the state, which supplies the brine to manufacturers and receives a royalty of one cent per bushel. The salt industries of Michigan are of quite recent devel meat, although as early as 1838 unsuccessful efforts had been made by the state authori ties to work the valuable licks and springs. In 1859, prompted by the offer of a bounty
of 10 ets. a bushel, offered by the legislature for salt made ia the state, a company was organized in East Saginaw, and in a few years the production of salt had reached such extensive proportions as to largely encroach upon the market formerly commanded by New York. Nearly 700,000 bush. are now made yearly in Michigan. West Virginia, Ohio, and Pennsylvania have each of 'them at different periods been among the lead ing states in the union in this branch of industry, but they have seriously declined of late years. In Indiana, Illinois, Kentucky, and the New England states, the business has become unproductive; in Missouri and Tennessee it has been abandoned. Some of the western states and territories, Kansas, Arkansas, New Mexico, Utah, and California, contain important saline springs and lakes, which have been only slightly worked as yet, and which with &lie settlement of the country will prObably be fully developed. In Louisiana the deposit of rock-salt in Petit Anse (see SALT DEPOSIT IN LOUISIANA) yields about 100,000 bush. annually. The demand for salt in the United States, how ever, is still largely supplied by importation, especially from Canada, the 'arnual con sumption being placed at nearly 40,000,000 bush., and only about one-half of that amount is of home production.
Agricultural uses.—These are two-fold: first, as a fertilizer of the soil, and second, as a necessary article of food for farm stock. Salt can be only sparingly used as a mannre; its effects depend so much not only upon the character of the crops, but also on the nature of the soil, that in the hands of an ignorant person it is liable to do more harm than good. In the rice fields of the east sea-water is said to have been used from a very early antiquity with beneficial results. In sandy soils, especially in those devoted to the cultivation of mangold-wurtzel, the English farmers have found salt very successful and it is also recommended as a top-dressing in pasture-lands, checking the rank growth of the grass, but greatly increasing its quality and succulence. Used in connection with nitrate of soda, in the proportions of two parts of salt to one part of nitrate of soda, the beneficial effects of the latter manure are largely increased. On stiff soils, however, salt is practically inoperative, and in many cases where its use has been recommended, as in the growth of cereals, cabbage, etc., experience has shown thaVit is of little or no benefit. As an essential portion of the food of live stock salt is a necessity upon every farm. Animals which are subject to lively exercise during the day are especially dependent upon salt for their health, and instances are rot uncommon where beasts of burden have died for want of it. Mulch cows, it is well known, need a daily allowance of salt in order to preserve the sweetness of their milk, and the quality of the fleece of sheep depends to a great extent upon their obtaining a sufficient measure of salt. A custom practiced by many farmers, which may be generally recommended, is that of keeping a stock of salt in the corner of a pasturage to which ready access is had by the cattle, there being no danger of their eating more than nature requires, except in cases where it had pre viously been denied them for an undue length of time.
_Industrial uses.—It is estimated that more than one-half of the total amount of salt consumed in this country is used in the packing and preserving of meats and fish, and the preservation of the products of the dairy. In the case of beef and pork a small por tion of saltpeter is often added to the salt, which withdraws the moisture from the meat. Sugar is also used in connection with salt in the curing of hams. For dairy purposes none but the finest grades of salt should be used; in the packing of beef and pork the coarser kinds are the best. It has often been suggested that salt might be employed advantageously iu the seasoning of timber, but experience teaches that timber so sea soned is liable to contract moisture, with all the attendant evils of warping and increas ing in bulk and in weight. Of course, in the case of wood-work constantly exposed to water, as in the joints and intersections of ships, this objection does not hold, and the experiment in such cases has often been tried with success. In refrigerating mixtures salt is invaluable, and in the manufacture of ice-cream large quantities of salt are annually consumed. As salt is the source from which soda is derived, it is really the basis in the manufacture of soaps and glass. In the United States, however, very little salt is converted into soda, the latter article being principally imported. England turns fully one-half of its annual production of salt into soda-ash. Other chemical products of salt are the chlorine used in the bleacheries and hydrochloric or muriatic acid—the latter being formed in the manufacture of soda.