The American Cyclopædia (1879)/Salt

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SALT, sodic chloride, sea salt, or common salt, the substance which is always denoted when the word “salt” is used in ordinary language. The word is derived from the Greek, in which ἅλς in the feminine is used for the sea, and ἅλς in the masculine for the solid product left when sea water evaporates. It is sometimes also called muriate of soda. It may be formed by burning sodium in chlorine gas, or by neutralizing hydrochloric acid with sodium carbonate, and evaporating. It occurs very abundantly in nature, both in the solid state, as rock salt, and in solution in sea water, salt lakes, and salt springs; also in smaller quantity in river water. Mines of rock salt have been recently explored in the Caucasus, in which the stone implements were found as they were left at a date so remote that no tradition exists of the time when they were worked. The mines of Wieliczka in Austrian Galicia have been worked for at least six, but probably for upward of eight centuries. The springs of Droitwich in England were worked by the Romans, and in Cheshire “the Wiches” were very productive in the reign of Edward the Confessor. Little is understood of the origin of rock salt. Some beds, as those of Cheshire, appear to have been produced by the drying up of bodies of sea water cut off from the ocean, while in other cases, as at Bex, where the salt forms a perpendicular vein or dike, its origin is altogether obscure. Salt lakes are derived either from the partial drying up of isolated bodies of sea water, as the Dead sea, or by the evaporation of lakes without outlets, and fed by streams which have passed over beds of salt, or plains impregnated with it, as Great Salt lake, Lake Urumiah in Persia, and many of the lakes of South America. Saline incrustations often overspread the surface of plains in Russia, India, the South American pampas, and the regions E. and W. of the Rocky mountains. The salt of the ocean has doubtless resulted from the chemical changes which have taken place between the elements that constitute the earth's crust during former geological epochs. The waters of the open ocean contain on an average 33.8 parts of salt in 1,000, of which 26.8 in 1,000 are common salt, equal to about 4 oz. in a gallon, or a bushel from 300 or 350 gallons. The entire quantity of salt in the ocean is estimated by Schafhäutl at 3,000,000 cubic miles. The water of landlocked seas like the gulf of Mexico or the Mediterranean sea contains more salt than that of the open ocean, and it is also found that the water of the bottom of such seas is salter than that upon the surface.—Salt crystallizes in colorless, transparent, anhydrous crystals, belonging to the isometric system, and has a very perfect cubic cleavage, which generally displays itself even in the great masses of rock salt, parts of which however are frequently massive and granular, and rarely fibrous or columnar. But the most characteristic peculiarity of the crystallization of salt is the formation of the hopper-shaped crystals on the surface of a saline solution during evaporation. A single cube appears at first, which partially sinks in the liquid, and new cubes then form and attach themselves to its upper edge, till by a repetition of this process a hollow rectangular pyramid, sometimes of considerable dimensions, and with the apex downward, is finally produced. Crystals of this form occur in some salt mines, and casts of them in clay are found in the New York salt region and some other places. Salt has a specific gravity of 2.1 to 2.257, and a hardness between gypsum and calc spar. It is transparent to translucent, and its color varies from white to yellowish, reddish, bluish, and purplish. It is of all substances the most perfectly diathermanous or transparent to heat of every degree of refrangibility. (See Diathermacy.) At 32° F. 100 parts of water dissolve 36.52 parts of pure salt; and at 229.5°, the boiling point of a saturated solution, only 40.35 parts are dissolved. This almost uniform solubility at all temperatures furnishes the means of separating it from many of the foreign salts with which it is associated in sea water and brine springs. Rock salt dissolves much more slowly, even in fine powder, than sea salt and that from springs, and the coarsely crystallized salt than the finer varieties. These differences are of economical importance, especially in curing provisions. For the principle of its curative properties see Preservation of Food. The freezing and boiling points of solutions rise with the degree of concentration. Salt is fusible at a red heat, and volatile at a still higher temperature. Its volatility is made use of in the process of “salt-glazing” common earthenware. (See Pottery and Porcelain, vol. xiii., p. 788.) Artificial crystals generally decrepitate when heated, from the presence of water mechanically enclosed between their layers. Some specimens of rock salt from Wieliczka decrepitate when dissolved in water, and disengage a gas, which is sometimes pure carburetted hydrogen, and sometimes a mixture of this with hydrogen and oxide of carbon.—Salt is a compound of one atom of chlorine combined with one atom of sodium; chemical symbol, NaCl; molecular weight, 58.5. When it is heated to redness with silica, silicate of sodium and hydrochloric acid are formed. A process for manufacturing soluble glass is based on this reaction. With oil of vitriol it gives sulphate of sodium and hydrochloric acid. This is the first step in Le Blanc's process for soda ash. Salt is rarely if ever ob- tained pure. The chief impurities in rock salt are sulphate of lime, oxide of iron, and clay; but besides these the chlorides of potassium, calcium, and magnesium, the sulphates of soda and magnesia, and bituminous matters are occasionally met with, and some varieties are even colored by the presence of infusoria. In salt made from sea water, the salts of magnesia with a little sulphate of lime are the principal impurities. All the varieties of salt occasionally contain minute quantities of bromides and iodides. The following table exhibits the composition of salt from various sources:

 of magnesia 
and soda.
 Carbonates.[1]   Alumina 
 Residue.   Water.   Percentage 
of saline

Wieliczka, white  100.00 . . . . . . . . trace . . . . . . . . . . . . . . . . . . . . . . . .  Bischof.
Berchtesgaden, yellow 99.928  . . . . . . . . 0.07 . . . . . . . . . . . . . . . . . . . . . . . .  Bischof.
Hall In Tyrol   99.43   . . . . 0.25 0.12 . . 0.20 . . . . . . . . . . . . . . . . . . . .  Bischof.
Stassfurt   94.57 . . . . . . . . 0.97 . . 0.89 . . . . . . 1.12 2.23 0.22 . . . .  Heine.
Hallstadt in Upper Austria   98.14 trace . . . . . . . . . . 1.86 . . . . . . . . . . . . . . . . . . . .  Bischof.
Vic in German Lorraine   99.80 . . . . . . . . . . . . . . 0.50 . . . . . . 0.20 . . . . . . . . . .  Berthier.
Jeb-el-Melah, Algeria   97.00 . . . . . . . . . . . . . . 3.00 . . . . . . . . . . . . . . . . . . . .  Fournet?
Ouled Kebbah, Algeria   98.58 . . . . 0.93 0.54 . . . . . . . . . . . . . . . . . . . . . . . .  Fournet.
Cheshire, England   99.52 . . . . . . . . 0.02 . . 0.46 . . . . . . . . . . . . . . . . . . . .  G. H. Cook.
Carrickfergus, Ireland   96.28 . . . . . . . . . . . . . . 3.50 0.08 . . . . . . . . . . 0.14 . . . .  G. H. Cook.
Holston, Virginia   99.55 . . . . trace . . . . . . . . . . . . 0.45 . . . . . . . . . . . . . .  C. B. Hayden.
Petite Anse, Louisiana   98.88 . . . . trace trace . . 0.79 . . . . . . . . . . . . . . 0.33 . . . .  Goessmann.
Santo Domingo   98.33 . . . . . . . . 0.04 . . 1.48 . . . . . . . . . . 0.01 0.07 . . . .  Goessmann.
Turk's island   96.76 . . . . . . . . 0.14 . . 1.56 0.64 . . . . . . . . . . 0.90 . . . .  G. H. Cook.
St. Martin's   97.21 . . . . . . . . 0.26 . . 0.54 0.24 . . . . . . . . . . 1.75 . . . .  G. H. Cook.
St. Kitt's   99.77 . . . . . . . . 0.01 . . 0.08 . . . . . . . . . . . . . . 0.14 . . . .  G. H. Cook.
Curaçoa   99.85 . . . . . . . . 0.03 . . 0.12 . . . . . . . . . . . . . . . . . . . .  G. H. Cook.
Cadiz   95.76 . . . . . . . . 0.57 . . 0.75 0.48 . . . . . . . . . . 2.44 . . . .  G. H. Cook.
Lisbon   94.17 . . . . . . . . 1.11 . . 0.49 1.39 . . . . . . . . . . 2.84 . . . .  G. H. Cook.
Trapani, Sicily   96.78 . . . . . . . . 0.49 . . 0.41 0.68 . . . . . . . . . . 1.64 . . . .  G. H. Cook.
Martha's Vineyard   94.91 . . . . . . . . 0.24 . . 1.42 0.19 . . . . . . . . . . 3.24 . . . .  G. H. Cook.
Texas   99.46 . . . . . . . . . . . . . . 0.10 0.30 . . . . . . . . . . 0.14 . . . .  G. H. Cook.
Cheshire, England   96.36 . . . . 0.01 0.02 . . 1.17 . . . . . . . . . . . . . . 2.44 . . . .  G. H. Cook.
Dieuze, German Lorraine   97.59 . . . . . . . . . . . . . . 1.02  0.89[2] . . . . . . . . . . 0.50 . . . .  G. H. Cook.
Droitwich, England   96.93 . . . . . . . . 0.02 . . 3.05 . . . . . . . . . . . . . . . . . . . .  G. H. Cook.
Goderich, Ont.   97.08 . . . . 0.01 0.03 . . 1.43 . . . . . . . . . . . . . . 1.50 . . . .  Goessmann.
Onondaga, N. Y.   97.41 . . . . 0.15 0.18 . . 1.26 . . . . . . . . . . . . . . 1.00 . . . .  G. H. Cook.
Pittsburgh, Pa.   96.70 . . . . 0.53 0.07 . . . . . . . . . . . . . . . . . . 2.70 . . . .  G. H. Cook.
Kanawha, W. Va.   91.31 . . . . 1.26 0.43 . . . . . . . . . . . . . . . . . . 7.00 . . . .  G. H. Cook.
Holston, Va.   99.11 . . . . . . . . . . . . . . 0.68  0.11[2] . . . . . . . . . . 0.10 . . . .  G. H. Cook.
Saginaw, Mich.   92.97 . . . . 1.09 0.50 . . 0.33 . . . . . . . . . . 0.01 5.10 . . . .  
Hocking Valley, O.   95.07 . . . . 0.61 0.04 . . 0.10 . . . . . . . . . . . . . . 3.40 . . . .  Goessmann.
Pomeroy, O.   96.42 . . . . 0.53 0.18 . . . . . . . . . . 0.05 0.16 2.66 . . . .  E. S. Wayne.
Nebraska   98.12 . . . . . . . . 0.07 . . 0.24  0.39[3] . . . . . . . . . . 0.80 . . . .  Goessmann.
Kansas   93.06 . . . . . . . . 0.24 . . 1.12  0.35[3] . . . . . . . . . . 4.80 . . . .  Goessmann.
Onondaga, “factory filled”   98.28 . . . . . . . . . . . . . . 0.91 0.09 . . . . . . 0.12 0.60 . . . .  Goessmann.
Great Salt lake   97.61 . . . . . . . . . . . . . . 1.03 0.08 . . . . . . . . . . 1.28 . . . .  G. H. Cook.
Elton lake, Russia   98.95 . . . . . . . . 0.19 . . 0.51  0.35[2] . . . . . . . . . . . . . . . .  Göbel.
Halle in Prussian Saxony   94.43 0.21 1.03 1.69 . . 2.23 . . . . 0.89 . . . . . . . . . . 12.28  Meissner.
Stassfurt   94.49 . . . . . . . . 0.99 0.34 2.80  1.20[2] 0.18 . . . . trace . . 17.16  Heine.
Schönebeck   95.71 0.08 . . . . 1.09 0.08 1.61 1.37 0.06 . . . . . . . . . .  2.00  Herrmann.
Artern, from bore in rock salt    95.35 0.45 . . . . 1.59 1.10 1.51 . . . . . . . . . . . . . . . . 26.50  Heine.
Dürrenberg   89.88 . . . . . . . . 1.49 0.99 0.04  0.63[2] 0.17  6.77[4] 0.02 . .  8.39  Heine.
Nauheim   82.23 1.83 6.74 1.18 . . 0.18 . . . . 7.68 . . . . 0.07 . .  2.87  Bromeis.
Soden   86.01 1.81 . . . . 2.24 . . 0.65 . . . . 8.79 . . . .  0.50[5] . .  1.27  Figuier and Mialhe.
Cheshire   97.40 . . . . 0.25 0.25 . . 1.90 . . . . . . 0.20 . . . . . . 26.00  Wm. Henry.
Dieuze   84.87 . . . . . . . . . . . . . . 1.83  3.30[2] . . . . . . . . . . . . 15.20  G. H. Cook,
China   75.47 . . . . 17.92  5.97 . . . . . . . . . . . . . . . . . . . . 21.20  Boussingault.
Onondaga   95.42 . . . . 0.84 0.64 . . 3.09 . . . . . . 0.01 . . . . . . 18.54  G. H. Cook.
Pittsburgh   81.27 . . . . 13.93  4.80 . . . . . . . . . . trace . . . . . .  2.80  G. H. Cook.
Kanawha   79.45 . . . . 16.48  4.07 . . . . . . . . . . trace . . . . . .  9.20  G. H. Cook.
Holston   98.39 . . . . . . . . . . . . . . 1.22  0.39[2] . . trace . . . . . . 26.40  G. H. Cook.
Salt lake, Texas   97.08 . . . . . . . . . . . . . . 0.82  2.10[2] . . . . . . . . . . . . 24.90  G. H. Cook.
Sea water   78.61 1.34 . . . . 8.56 . . 3.47  6.42[2] 0.27 . . . . . . . . . .  3.74  Usiglio.
Elton lake   13.15 0.79 . . . . 67.80  . . . .  18.26[2] . . . . . . . . . . . . 29.13  Rose.
Dead sea   29.86 2.51 11.81  55.45  . . 0.37 . . . . . . . . . . . . . . . . 26.42  Booth and Muckle.
Great Salt lake   90.07 . . . . . . . . 1.12 . . . .  8.18[3] . . . . . . . . . . . . 22.42  L. D. Gale.

An examination of this table will show that the impurities differ both in kind and in quality. More or less sulphate of lime and chloride of magnesium are found in salt from whatever locality or source it may be derived. The purest rock salt is the best of all; next to that is sea salt, and then the average quality from brine springs; but the table shows that the “Onondaga factory filled salt” is as pure as the rock salt of Cheshire, England, which is one of the purest known. An impurity of 3 per cent. renders salt unfit for domestic purposes, especially if the impurity consist of chlorides of calcium and magnesium, particularly the former. Beds of rock salt and brine springs occur in geological formations of almost every period. The New York springs are in the upper Silurian, and most of those of western Pennsylvania and Virginia, of Michigan, Ohio, Indiana, Illinois, and Kentucky, in the lower coal measures; most of the Russian mines and springs are in the Permian; those of Cheshire in England, Ireland, eastern France, Würtemberg, and many other parts of Germany, in different members of the triassic group; those of the Austrian Alps in oolitic beds; those of the Pyrenees and of Cardona in cretaceous rocks; while those of Wieliczka in Galicia, of Tuscany, Sicily, and Petite Anse belong to tertiary strata. Its most invariable mineral associate is gypsum or hydrated sulphate of lime; in some places, as at Bex in Switzerland, this is replaced by anhydrite, or the same mineral without water; while polyhalite (a mineral consisting of sulphates of lime, magnesia, potash, and soda), bitumen, sulphur, and calc spar also frequently occur with it; and in many places, as in the wells in the coal formation, a copious discharge of carburetted hydrogen gas accompanies the flow of brine, and also jets of rock oil. (See Petroleum, vol. xiii., p. 370.)—Geographically salt is widely distributed. Excepting Norway, Denmark, and Holland, the European countries are all provided with salt to some extent from domestic sources, and even in some of these rock salt is imported and refined. The principal mines of rock salt are those of Wieliczka in Galicia; at Hall in the Tyrol, and along the mountain range through Aussee, in Styria, Ebensee, Ischl, and Hallstadt in Upper Austria, Hallein in Salzburg, and Reichenhall in Bavaria; in Hungary in the county of Mármaros; in Transylvania, Moldavia, and Wallachia; at Vic and Dieuze in German Lorraine; at Bex in Switzerland; in the valley of Cardona and elsewhere in Spain; in the region around Northwich in Cheshire, England; near Carrickfergus, Ireland; and in the government of Perm in Russia. The principal salt springs are in Cheshire, Worcestershire, and Staffordshire, England; in Würtemberg and Prussian Saxony; and in northern Italy. Russia is almost the only country which derives much from salt lakes. France, Spain, Portugal, and Italy, with a number of the islands of the Mediterranean, are the principal producers of sea salt. England, Austria, France, Spain, Portugal, and Italy, with some of the Mediterranean islands, are the principal exporters of salt.—In Russia the supplies from mines, springs, and lakes are inexhaustible. Over the vast area of the Permian group, covering upward of 300,000 sq. m., salt is found, and in numerous localities is extensively and profitably worked. Ancient mines of rock salt have been explored in the Caucasus, supposed to be among the oldest in the world. In Sweden, Carlstad near the N. shore of Lake Wener produces some salt, but both Sweden and Norway import much, principally from England and Sardinia. Denmark is also a large importer. In Holland and Belgium refined salt is made from British rock salt, which is dissolved in fresh or sea water, and crystallized by artificial heat. Among the largest salt mines in the world are those of Stassfurt in Prussia, and the adjoining Anhalt mines.—In the Austrian empire, Upper Austria, Salzburg, Styria, and Tyrol on the west, and Croatia and Dalmatia on the south, have almost inexhaustible stores of rock salt and brine springs; while the province of Istria derives much wealth from the lagoons bordering the Adriatic. The salt mines of Wieliczka, 7 m. S. E. of Cracow, extend over a space of about 2 m. in length by nearly 1 m. in breadth, and are about 1,000 ft. in depth. The salt occurs in great lenticular masses, inclined at a high angle. It varies very much in quality; the so-called “green salt” contains 5 or 6 per cent. of clay, which destroys its transparency; a variety called śpiza is crystalline and mixed with sand; while that known as szybik, principally from the lower levels, is in largely crystallized masses, perfectly pure and transparent. The strata in which it occurs are compact tertiary clays, containing fossils; and the principal associated minerals, besides gypsum, are bitumen, anhydrous sulphate of lime, the sulphates of baryta and strontia, and sulphur. The mines are entered by numerous shafts, with galleries at seven different levels, leading to a labyrinth of passages and immense excavations extending to a total length of upward of 500 m. Some of the chambers formerly excavated were more than 150 ft. high, but those now made are much smaller. One of these is fitted up as a chapel dedicated to St. Anthony, in which the altar, statues, columns, pulpit, &c., are all of salt. In another part is a lake 650 ft. long and 40 ft. deep, formed by the water which trickles through the strata. The annual yield is now about 1,400,000 cwt. It is not known when these mines were discovered. They are believed by recent authorities to have been worked in the early part of the 11th century, when they belonged to Poland, and in the 14th Casimir the Great established regulations for their working, as they had then become very productive. They were pledged to Austria in 1656, but recovered by John Sobieski in 1683. In 1772, when the first dismemberment of Poland took place, Austria again obtained them, and, except from 1809 to 1815, has since held them. The kings of Poland drew considerable revenues from these mines, and depended upon them for the dowries of their queens and the endowments of their convents, to which last purpose their revenues were applied as early as the 14th century. At each royal election the nobles always stipulated that the salt of Wieliczka should be supplied to them at the mere cost of extraction. From Wieliczka a saliferous region extends on both sides of the Carpathians, through Galicia, Hungary, and Transylvania, into Wallachia and Moldavia. The richest mines of Hungary are in the county of Mármaros. In Transylvania the mines have been worked since the times of the ancient Romans, and there is also a large number of salt springs.—In Switzerland the brine springs of Bex have been worked since the middle of the 16th century. They formerly belonged to a family of Augsburg named Zobel, but are now the property of the government of the canton (Vaud). In 1823, in consequence of the gradual failure of the springs, the mountain was pierced by a gallery, which led into a vein or dike of salt, varying from 2 to 50 ft. in thickness. Springs are found in other parts of Switzerland. In Italy the lagoons and springs, still highly productive, were worked in ancient times. Venice formerly owed her prosperity in great part to her salt lagoons and her control of the trade in salt in southern Europe. During the decline of her power her salines remained unproductive, until they were reëstablished on a vast scale during the French rule. They are again largely worked in the artificial enclosures aronnd the city connected with the sea. Salt is a strict government monopoly, and the springs and salines furnish one of the chief articles of export.—Spain has one of the most remarkable salt mines in Europe, at Cardona in Catalonia. Here is a hill 500 ft. high, covering an area of three quarters of a square mile, composed of nearly vertical beds of salt, gypsum, and clay belonging to the cretaceous series, the salt constituting about four fifths of the entire mass. The workings are in the form of long steps of one metre (39 in.) in height and width, cut in the salt, in the open air, by means of blasting and the pick. The salt is simply ground and washed to prepare it for sale. Salt springs are found in other parts of Catalonia and along the Pyrenees, in beds of the same age, as at Pamplona in Navarre. But most of the salt of Spain is obtained from sea water, especially in Valencia and Catalonia. Salt is a strict monopoly in Spain, and can be sold by individuals only for exportation.—In Portugal salt is manufactured principally from sea water, and the business is largely carried on, sustaining a considerable export and coasting trade. The St. Ubes salt, well known in commerce, and much esteemed for packing provisions, is a product of Portugal. The export, and that of the Cape Verd islands also, is principally to Brazil and the United States.—In France, which by the treaty of 1871 has lost its principal rock salt deposits of Vic and Dieuze, formerly comprised in the department of Meurthe, there are both important deposits and springs in the adjoining regions, along the Jura, and in the central departments. Along the Pyrenees rock salt and springs are found in the cretaceous formation. But the greatest portion of the product of France is from the lagoons on the Atlantic and Mediterranean coasts.—England, which now produces more salt than any other country, obtains her supply almost exclusively from mines and springs in beds of the same geological age as those of Vic and Dieuze, principally in Cheshire and Worcestershire; there are also brine springs in Staffordshire, from which Hull is supplied. Northwich and Winsford in Cheshire, on the river Weaver, furnish six sevenths of the whole; and the beds of rock salt are chiefly limited to the region drained by this river. They occur in detached masses of limited area beneath the plains of this district, sometimes spreading out, as at Northwich, to a breadth of three fourths of a mile. The strata penetrated at this locality are gypsiferous clays and marls to the depth of 120 ft., below which are found beds of salt 60 to 90 ft. thick, resting on 80 to 40 ft. of indurated clays containing seams of rock salt, and below these rock salt about 100 ft. thick. The purest salt is in a portion of 4 ft. thickness about 10 or 12 ft. above the bottom of the upper bed, and in another of 20 ft. thickness 60 or 70 ft. below the top of the lower bed. Other portions of the beds are earthy. The salt is not stratified, but divided into vertical prisms sometimes 3 ft. in diameter. But the Cheshire salt, known in commerce as Liverpool salt, is mostly obtained from wells of 200 to 250 ft. depth, terminating in the lower bed of rock salt. In these the brine is pumped up and conveyed to the evaporating pans, which are 20 ft. wide, 30 to 80 ft. long, and 16 to 20 in. deep. In Scotland, before the abolition of the duty, much salt was made, from sea water, but most of the salt works are now abandoned. In Ireland two beds of rock salt, making together a thickness of 120 ft., covered by 630 ft. of red marls, were discovered about 1853 at Carrickfergus near Belfast; since which time the annual product has gradually increased to many thousands of tons.—The total product of the mines and springs of Europe was estimated in 1821 at 1,250,000 to 1,500,000 tons. It is now certainly twice as great as the larger of these estimates; and with the addition of that from sea water and salt lakes, the total product is probably 5,000,000 tons.—In Asia salt is no less abundant than in Europe. In Siberia and Tartary plains are covered with saline incrustations. Extensive mines of rock salt have been worked from ancient times at Nakhitchevan in Armenia. This variety abounds in Persia, where are also many salt lakes with no outlets. Lake Urumiah, 90 m. long and 20 to 30 m. broad, and about 4,300 ft. above the sea, contains brine of extraordinary strength, the percentage of pure salt being 18.116 and of other salts 2.434. Its specific gravity is 1.155. In summer, over a breadth of 3 or 4 m. around parts of this lake, the incrustation of salt is sometimes more than a foot thick. The resources of British India in salt are great, but comparatively unimportant from the monopoly of the government, and salt is largely imported from England. Still vast beds of rock salt are worked in the Punjaub at the foot of the Himalaya, and great quantities are obtained from the incrustations over the plains near the mouth of the Indus, and from various other portions of the Indian peninsula. The salt wells of China are remarkable for their great depth and immense numbers. China and Java are wholly dependent upon their own resources for salt, admitting no importations.—Africa contains extensive tracts of salt lands and beds of rock salt in the desert of Sahara, particularly in the N. and W. portions, as in that, part called Tanezruft, on the route between Tuat and Timbuctoo. The trade in salt with Soodan furnishes a support for many of the inhabitants of the desert. Near Biskra is a mountain of salt in the cretaceous formation; and another is found near the salt lake Zagrez. This lake is in some seasons covered with a glistening white crust of excellent salt, like ice, amounting to even one or two feet in thickness. Similar lakes are met with in this region, and also in Abyssinia. In central Africa, salt from salt lakes is perhaps the most important article of commerce.—In the Hawaiian islands salt is procured from the lakes near Honolulu, and is exported.—In South America, rock salt is found in Brazil, Peru, Colombia, and Venezuela; in the pampas of the south and the elevated plains of Peru, it occurs as an incrustation; in Patagonia and the Argentine Republic are productive salt lakes; in Colombia it is obtained from springs, and in Brazil from lagoons on the coast. The salines or salt lakes of the pampas extend from Port St. Julian in Patagonia, lat. 49° S., through the Argentine Republic, to lat. 25° S. They are generally shallow, and in the wet season the whole or a part of the salt is dissolved, and redeposited during the dry season, when the appearance of the snow-white expanse, crystallized in great cubes, is very striking. Patagonian salt is still a large article of commerce with other parts of South America. It is of the greatest purity, requiring no preparation, and containing only 0.26 per cent. of gypsum and 0.22 of earthy matter, without a trace of iodic salts. The beds of various salts in the elevated plains of Tarapaca in Peru, especially around Iquique, are among the most remarkable in the world. The porphyritic mountains on the coast rise abruptly to a height of between 1,900 and 3,000 ft.; between their summits and an inland plain, on which lies the celebrated deposit of nitrate of soda, is a high undulatory district, covered by a crust chiefly composed of common salt, either in white, hard, opaque nodules, or mingled with sand, forming a compact sandstone. This never attains a great thickness, though in the pampa of Tamarugal, in S. Peru, Mr. J. H. Blake saw a considerable space covered with round masses of salt, 5 or 6 ft. in diameter, piled upon each other. In some places they were deep red, but in the vicinity of Pisco they were sufficiently pure for culinary purposes. The inhabitants employed them in building their houses. As rain falls here only at intervals of many years, the deposits are subjected to very little waste. Colombia has very rich mines of rock salt, especially in the district of Zipaquira. The mineral extends many miles across a branch of the Cordillera. Salt springs are also found here. On the N. coast are lagoons of great capacity of production. The salt mines of Araya, in the peninsula N. of Cumaná in Venezuela, were discovered by the followers of Columbus in 1499; and as they offered an inexhaustible supply of the finest salt, they continued for years to attract adventurers of all nations. The Dutch islands of Curaçoa and Buen Ayre, N. of Venezuela, produce several hundred thousand barrels annually by natural evaporation and of the finest quality, much of which is exported to the United States. A large number of the West India islands produce salt, especially the southern Bahamas, Cuba, Porto Rico, St. Martin, and St. Christopher or St. Kitts. Turk's island, S. E. of the Bahamas, was formerly the main source of sea salt for the United States, and even now most of the salt from any of the West India islands, or from Yucatan, is called Turk's island salt. Since 1833 the manufacture has fallen off here, while it has grown up in the Windward islands and some other British islands. Of the Dutch West Indies, besides Curaçoa and Buen Ayre, St. Martin, in the Leeward islands, produces a great deal from lagoons in the southern part, and it is the principal export of Philisburg, the Dutch capital. On the N. coast of Cuba are extensive lagoons, from which in dry years large quantities are obtained. In Hayti there is a deposit of rock salt on the S. side of the island, said to form a mountain 6 m. long, ½ m. broad, and 400 to 500 ft. high. The crude salt contains 96.79 per cent. of pure sodium chloride. In Porto Rico are two salines formerly worked by the government, which, as well as the monopoly of the introduction of either Spanish or foreign salt into the island, were sold to private parties in 1851. Cuba and Porto Rico, however, draw most of their supply from Spain, and some from England.—In Central America are many salt springs, and on the Pacific coast large quantities are made from sea water. In Mexico, the state of Oajaca has salines extending for 30 or 40 leagues along the Pacific, which are very valuable and supply the whole interior of the state. These formerly belonged to the government, but were sold by Santa Anna to the family of Echeverria for $300,000. In Tamaulipas salt is produced from a chain of lagoons on the coast divided by the Rio Grande from the celebrated salt lake near Brownsville in Texas. The lake of Tezcuco, near the city of Mexico, is so strongly impregnated as to leave a white deposit on its banks, and supplies a number of salt works. The island of Carmen, in the gulf of California, contains a large salt lake, with a solid crust several feet thick. Large quantities are sent to Mazatlan and San Francisco.—In British North America, Nova Scotia, New Brunswick, Cape Breton island, Newfoundland, and the Magdalen islands contain salt springs, which in nearly all these places are associated with gypsum. At Goderich on Lake Huron, in 1866, in boring for oil, a deposit of rock salt was struck at a depth of about 960 ft., and the brine was remarkably strong and of great purity. The manufacture of salt was commenced immediately, and developed rapidly, until now the production amounts to several millions of bushels annually, affording the principal source of supply for Canada, and also furnishing a large amount for export to the United States. On account of the strength and purity of the brines, salt is produced and sold at a price which after adding the duty enables the Goderich manufacturers to compete with those of the middle and western states. Canada was formerly principally supplied from England and the state of New York; she has been indeed our only customer of importance, the exports of American salt to other countries being small.—The United States is well supplied with salt, 23 of the states and territories having been returned by the different censuses since 1810 as producers, while seven others possess valuable springs or deposits. Rock salt has been found only in S. W. Virginia and in Louisiana. The principal springs are in central New York, near Syracuse, in West Virginia and Pennsylvania, in Michigan, and in the states bordering on the Ohio. Salt lakes occur in California, Utah, New Mexico, Texas, and Minnesota. Salt has been made from sea water in nearly every Atlantic state at some period. The New England states have at different times produced large quantities of sea salt, particularly during the revolution and the war of 1812, and about 1830; since which time but little has been made, though a few vats are still kept in operation at Cape Cod, Nahant, &c. Virginia had salt works at Cape Charles before 1620, and in 1633 exported salt to Massachusetts. In South Carolina, Nathaniel Johnson undertook the manufacture in 1689, and in 1725 the legislature passed two acts for the encouragement of salt making.—The salt springs of New York are principally in Onondaga co., in the towns of Syracuse, Salina, and Geddes, and issue from rocks of upper Silurian age. They were known to the Indians at a very early period, but Father Lalemant is believed to have been the first white man who visited them. About 1770 Onondaga salt was in common use among the Delawares, and was carried to Quebec for sale. The first made by the whites was in 1788, near Syracuse, by boiling. The salines belong to the state, which supplies the brine to manufacturers and receives a royalty of one cent a bushel. Six cents was formerly charged, and the state thus derived a large revenue; but in 1846 the tax was reduced to its present amount, which suffices to defray the expenses of pumping, superintendence, &c. In 1789-'90, 500 or 600 bushels were made and sold at $1 a bushel. In 1791 the capacity of the works was 8,000 bushels a year. In 1797, when the first leases of salt lots were made, the product was 25,474 bushels; in 1807, 165,448; in 1817, 448,665; in 1827, 983,410; in 1837, 2,161,287; in 1847, 3,951,351; and in 1858, 7,033,219 bushels. In 1862 the production reached the maximum of 9,053,874 bushels; since that year the average has been about 8,000,000 bushels, gradually declining since 1870. For 1874 the product was 6,594,191 bushels. The productive springs are in great part found in the marshy lands which surround Onondaga lake. A stratum of marl 3 to 12 ft. thick, underlaid by a marly clay, forms an impervious barrier between the water raised from the wells and that of the lake. Wells are sunk or bored in the low lands around the lake, from 200 to 300 ft., and from these the salt water is forced up by pumps into the reservoirs from which the evaporating works are supplied. The strata passed through near the surface are beds of fine sand, and then clay, sometimes more than 40 ft. thick, beneath which is gravel of pebbles and sand containing salt water. The brine is of variable strength in the different wells, as indicated by its specific gravity, which is from 1.045 to 1.147, and from 30 to 45 gallons are required for a bushel of dry salt weighing 56 lbs. The chief impurity is sulphate of lime, which was found by Dr. Lewis O. Beck to amount to from 4.04 to 5.69 per cent. Excepting the chloride of magnesium, the impurities found in these brines are also common to rock salt. From the deepest wells at Syracuse Dr. Beck obtained brines which afforded 173.50 parts of salt in 1,000 parts, and of which 33¼ gallons were required to the bushel of ordinarily dry salt. The deepest wells now afford brines containing 17 to 20 per cent. of salt. Salt springs are found in other parts of central and also of western New York, especially over the area extending E. and W. 170 m. from Otsego co. to Orleans and Genesee, and N. and S. about 80 m. from Broome co. nearly to Lake Ontario.—In western Pennsylvania is an important salt region along the Alleghany, Kiskiminetas, and Beaver rivers, in the carboniferous series. In 1812 the first wells were bored 200 ft. deep on the Kiskiminetas river, and in 1829 there were extensive works there, using coal, and producing salt at 20 to 25 cts. a bushel, while in Kentucky, Ohio, and Illinois it was selling at 50 cts. The production of Pennsylvania in 1857 was estimated at 900,000 bushels; in 1860 it was 1,011,800 bushels, but it has since declined. West Virginia has very important salines in the valley of the Great Kanawha, beginning at Charleston and extending about 20 m. above. They are situated in the lower coal measures. The first wells bored were only 30 ft. deep, but some have since been bored 1,500 ft.; 700 or 800 ft. is as great a depth as is generally profitable, as below this the water does not increase, while the discharge of carburetted hydrogen gas becomes much more copious. This gas was formerly employed for heating the kettles, but its use is now almost discontinued. The bittern or residual liquor contains a good deal of bromine. In 1829 these works produced 1,000,000 bushels. The product for 1870 was 4,633,750 bushels, but for 1875 it was expected to amount to hardly one fourth of that quantity. In S. W. Virginia there is a salt region, in Washington and Smyth counties, along the banks of the N. fork of the Holston river. The Holston springs and rock salt are on the line of an extensive dislocation of the strata, bringing the lower Silurian magnesian limestones into immediate contact with the lower carboniferous strata, the vertical displacement being calculated by Prof. Rogers at not less than 8,000 ft. The dislocation is at least 100 m. long, but no rock salt or workable brine is found except in the Preston valley, on the line of Smyth and Washington counties. Several productive wells have been bored to the depth of 200 to 300 ft. In one well over 300 ft. of rock salt divided by a little clay was passed through without tapping any brine. There appears to be no solid rock, but a deposit of clay and earth, imbedding in places large bodies of rock salt and gypsum, and saturated in its lower portions with highly concentrated brine.—The first attempts in Ohio were made in 1798 at the “old Scioto salt works” in Jackson co. The wells were only 30 ft. deep, and 600 to 800 gallons were required to make a bushel of dark and inferior salt, which however sold for $3 or $4, being carried, even as late as 1808, on pack horses to considerable distances. Until about 1845 the wells were sunk only 400 or 500 ft. in depth, but at Pomeroy they are now 1,200 ft. deep, yielding a copious supply of strong brine, and more than two thirds of the salt of Ohio is at present manufactured in that vicinity. From some of the springs issue large quantities of carburetted hydrogen gas, which has been used as fuel in evaporating. Rock oil is also a product of them. (See Petroleum.) In 1850 Ohio produced 550,350 bushels, and in 1873 4,154,187 bushels. Indiana has numerous salt springs, especially along the Wabash river in the coal measures. The Wabash saline in 1809 made 130,000 bushels, and the United States saline, about 1820, at least 150,000 bushels; but in 1870 the whole product of Illinois was only estimated at 54,000 bushels. In Kentucky salt springs or licks are very numerous, and even before 1795 much salt was made. The principal licks are: one on Salt Lick creek, near the Ohio; the upper and lower Blue springs on Licking river; Drennon's lick, on the Kentucky river; Big Bone, Long, Bullett's, and Mann's licks. The principal works recently in operation are on Goose creek; they made in 1860 about 290,000 bushels, but the product in 1870 was only 64,000 bushels, and is now still less. In Michigan is a valuable salt region in Saginaw co. Many licks and springs have long been known, and in 1838 unsuccessful attempts were made by the state authorities to work some of them. In 1859 the legislature offered a bounty of 10 cts. a bushel for salt made in the state, and a company in E. Saginaw bored a well, and obtained at 669 ft. nearly saturated brine. Since 1860 the production of salt in Michigan has developed with great rapidity, until it has become next to New York the largest salt-producing state in the Union. The product in 1874 was 5,134,875 bushels. In 1862 a deposit of rock salt was discovered on the island of Petite Anse in Vermilion bay, off the coast of Louisiana. It is considered to be geologically more recent than the tertiary, or of quaternary age. It was worked extensively during the blockade of that coast in the civil war, and has since produced more than 100,000 bushels annually. In Kansas, the Indian territory, and western Arkansas, along the Arkansas and Washita rivers, in N. W. Texas, New Mexico, and Utah, is a vast expanse of sterile plains, principally occupied by cretaceous rocks, in nearly every part of which salt lakes and incrustations and vast masses of gypsum occur. But the most famous of these lakes is the Great Salt lake of Utah, about 75 m. long and 30 m. wide, whose waters are nearly saturated, containing 20.2 per cent. of common salt, and 2 per cent. of other salts. For several years the waters in this lake have gradually risen above their former level, and a proportionate diminution of salt has been observed. In California are numerous salt lakes, particularly in Tulare co., at the Cañada de las Uvas, and in the Taheechaypah pass of the Sierra Nevada, near which is a dry lake from which a considerable quantity fit for table use has been taken.—At the present time (1875) the production of salt in the United States may be considered in reference to three different sections, viz.: the region east of the Mississippi river, the Rocky mountain region, and the Pacific coast region. Although during the past 100 years salt has been manufactured in nearly every state east of the Mississippi river, the business is now mainly restricted to three separate areas: the neighborhood of Syracuse, N. Y.; Saginaw valley, Mich.; and the Kanawha valley, including the wells at Pomeroy, near the junction of that river with the Ohio. These three localities produced in 1870, in about 200 establishments, nearly 16,000,000 bushels of salt, the total number of establishments in the country at that time being 282, and the total production 17,606,000 bushels. From 1850 to 1875 the salt industry has grown in Florida and Michigan, while in New York and the Kanawha region it has gradually decreased since 1862, when the business appears to have been most flourishing. In Massachusetts, Pennsylvania, Kentucky, Indiana, and Illinois the business is rapidly becoming unproductive, while Missouri and Tennessee no longer report any saline in actual operation. But the total production for 1870 was greater than that for 1860 by about 5,000,000 bushels, nn increase of 40 per cent. The salt industry is now very much depressed, especially in the Kanawha valley and at Syracuse, from the fact that the great strength of the Michigan and Goderich brines and the abundance of fuel in those localities enable these brands of salt to be successfully sold where Onondaga salt made from brines only half as strong, and Ohio and Kanawha salt made from brines still weaker, formerly commanded the market. In addition to these disadvantages, the Onondaga and Kanawha salt is driven from eastern markets by Liverpool salt, which is brought to our eastern seaports at a merely nominal charge by ships that load in return tobacco, cotton, and breadstuffs. Throughout the region lying on both flanks of the Rocky mountains the demand is rapidly increasing, and is mainly supplied from local sources, chiefly brine springs. In 1870 Utah produced 1,950 bushels, Idaho 13,400, Colorado 7,500, and Kansas 10,000. The production is rapidly increasing with the settlement of the country, and is almost without competition. On the Pacific coast salt has long been produced near Los Angeles and further north, and the production increased from 44,000 bushels in 1860 to 174,835 in 1870. The salt is obtained entirely by evaporation of sea water. Salt was formerly produced in Oregon, but is not now manufactured there.—Manufacture of Salt. The separation of salt from brines and sea water is conducted in three distinct ways: 1, by evaporation by the heat of the sun in shallow reservoirs, principally practised with sea water in the southern temperate or tropical regions; 2, by artificial heat, in very long shallow pans, as in Cheshire, or in kettles, as at the Onondaga salines; 3, by exposing sea water to intense cold, when the ice formed is nearly pure, and a concentrated brine remains, which is afterward subjected to one of the first two processes. Weak brines are frequently brought to a certain strength by solar evaporation, and then finished by boiling; or more frequently they are pumped up into elevated reservoirs, and suffered to trickle over the surface of bundles of brush or thorns built up into walls, sometimes 30 to 50 ft. high and 5,000 ft. long, fully exposed to the sun and wind; the great amount of surface thus obtained causes the evaporation to go on very rapidly, and a few repetitions of the process bring very weak brines to suitable strength for boiling. This process is known as “graduation;” and the same effect is sometimes obtained by allowing the water to trickle over ranges of cords suspended perpendicularly. The third process is practised in northern Europe. In nearly every locality certain details are employed in the evaporation due to peculiarities in the brines, in the fuel employed, proximity to the sea, &c. As an illustration of the general methods employed when treating sea water, the operations at Berre near Marseilles are thus described by Dr. T. Sterry Hunt, in a paper published in the “Geological Survey of Canada” for the years 1853-'6. The waters of the Atlantic contain from 2.5 to 2.7 per cent. of common salt, and those of the Mediterranean about 3 per cent. While the latter therefore afford a stronger brine, the dry and hot summers of the southern shores are also more favorable for the evaporation (which is conducted without artificial heat) than the cooler and more rainy coasts of Brittany and La Vendée. The Mediterranean waters, moreover, contain about 0.8 per cent. of sulphates and chlorides of calcium, magnesium, and potassium; and from the residue, or mother liquors, after most of the common salt has been separated, it is found that salts of magnesia and potash and sulphate of soda may be obtained of almost equal value with the salt which is the primary object of the manufacture. The salines of Berre, however, where these operations are very successfully conducted upon a grand scale, do not use the strong sea water, but are supplied from a lake which, though connected with the tide, is freshened fully one half by streams from the interior. Other advantages afforded by the situation compensate for this weakness of the brine. The broad receiving basins of these salines must be so situated that they can be flooded at very high tides, and be protected by dikes against their incursions when supplies of salt water are not wanted. A clayey soil is important to prevent infiltration, and give strength to the dikes. The water being let into the great shallow basins, it is allowed to remain till it deposits its sediments and begins to evaporate by the warmth of the sun. It is thence conducted successively through other basins of 10 to 16 in. depth, in which the evaporation goes on, and the lime it contained is deposited as a sulphate. As its bulk decreases smaller shallow basins suffice for holding it after it is separated from the sediments and lime, and in these it is concentrated by continued evaporation to a saturated brine. When this marks 25° Baumé, it is transferred to the salting tables, upon which the crystalline crusts soon collect. Pure salt to the extent of 25 per cent. of the whole product separates between 25° and 26°, and may be kept by itself, the brine in this case being removed to another table. Upon this salt of second quality is deposited to the extent of 60 per cent. of the whole, between 26° and 28.5°; and upon other tables the remainder is collected between the last degree named and 32°. The last product, though somewhat impure and deliquescent from the magnesian salt it contains, is preferred for salting fish on account of its property of attracting moisture. The mother liquors are run off to be treated for the other salts. From the salting tables the crystallized salt is taken and made up into pyramidal heaps, and during the summer season these are left exposed to the weather. The little rain that falls promotes the purification of the salt by removing the more soluble foreign matters. Nothing more is done to prepare the salt for the market. Its average price is one franc for 100 kilogrammes (220 lbs.). Steam or horse power is employed at these large salines to raise the water from the lower basins into the upper ones; the machines that take up the water are lifting wheels of 8 to 16 ft. diameter. The evaporating surfaces cover 815 acres, of which 1/10 is devoted to the salting tables. The total annual product of salt is about 44,000,000 lbs. At Baynas, as M. Pay en states, the same amount is made with strong sea water on 370 acres.—The relative strength of the various brines employed in the United States and Canada for the manufacture of salt is thus given by Dr. Beck, the figures representing the number of gallons required to the bushel of ordinary dryness:

Sea water, from 300 to 350
Boon's Lick, Mo. 450
Conemaugh, Pa. 300
Jackson, O. 213
Lockhart's, Miss. 180
St. Catharine's, Ont. 120
Zanesville, O. 95
Grand river, Ark. 80
Kanawha, W. Va. 75
Montezuma, N. Y. (old wells) 70
Muskingum, O. 50
Montezuma, N. Y. (new well) 50
Onondaga, N. Y. (old wells) 40 to 45
Onondaga, N. Y. (new wells at Syracuse) 30 to 35

At Saginaw, Mich., the proportion is 25 to 30 gallons to a bushel, and at Goderich, Canada, 22. The following description of the methods employed in treating the brines of Onondaga, N. Y., will serve as an illustration of those generally employed elsewhere, especially in Michigan, Ohio, and West Virginia. These brines contain about one half of one per cent. of sulphate of lime, a very small percentage of the chlorides of calcium and magnesium, mere traces of carbonic acid and oxide of iron, and from 16 to 17 per cent. of salt. It is the object of the manufacturers to remove all of the iron, a part of the sulphate of lime, and as much as possible of the chlorides of lime and magnesium. The colorless and clear brine is first pumped into shallow vats, where it remains until the carbonic acid escapes and the iron is deposited as oxide. It is then either evaporated by the sun's heat for “solar salt,” or by artificial heat for fine or boiled salt. The first process is conducted in wooden vats protected by movable covers, sheds with sectional movable roofs being generally used. The evaporation is conducted very slowly, and as a consequence the salt appears in very large crystals and is known as “coarse salt.” The brine from which the iron has been separated is drawn into a lower set of vats, where it is left until crystals of salt appear on the surface. A considerable amount of sulphate of lime has meantime been deposited. The resulting saturated brine, called “salt pickle,” is drawn off from the precipitated gypsum into a third set of vats. Whenever a sufficient amount of salt crystals has accumulated, they are washed in fresh pickle and allowed to drain from perforated wooden troughs, and thence removed to the storehouse. Three crops are produced in a season, the middle crop being the best. This coarse salt is considered best for packing meats and fish, as it dissolves more slowly than fine salt and prevents the meats from being packed too closely. Boiled salt is produced by several methods, of which three are the most important, viz.: the kettle, the pan, and the steam processes. In the first, most frequently employed in this country, from 50 to 60 kettles, having a capacity of from 100 to 120 gallons each, are set in a row and heated by a common flue and fireplace. Two rows are attached to one chimney. The settling tanks and store rooms are arranged along the sides of the kettles, and the whole roofed over. The precipitation of the iron is sometimes hastened by the addition of a small quantity of milk of lime. The clear brine is then drawn into the kettles, when evaporation goes on rapidly and at a higher temperature; consequently a larger proportion of the sulphate of lime separates before saturation than in the solar process. The removal of this precipitate is effected by placing an iron pan upon the bottom of the kettle, provided with an upright handle. The motion of the boiling liquid causes the particles of solid matter to collect in the central portion of the bottom upon the pan. The pan is removed and emptied from time to time until crystals of salt appear, when it is not replaced. The salt which accumulates is well washed in the remaining pickle and placed in baskets suspended over the kettles, when after draining a few hours it is emptied into the store rooms. A state law in New York prescribes that the salt shall be stored two weeks; also that it shall be inspected before being stored, and again when ready for shipment. The pan process is used in this country to some extent, and largely in England. The brine is either saturated cold or in a pan called the “foreheater.” It is then transferred to another pan and evaporated, either slowly or rapidly as a coarse or a fine salt is desired. If a very fine grain is desired, the pans are constantly stirred. The pans are of iron, set over flues, and vary in size from 60 to 20 ft. in length and 35 to 13 ft. in width, by 15 to 20 in. in depth. In these pans the evaporation is very rapid; the salt accumulates constantly, and requires to be withdrawn continually. In the steam process the brine freed from iron is drawn into the steam settlers, where it is brought to saturation. These are wooden cisterns about 100 ft. long, 8 ft. wide, and 6 ft. high. They are heated by several four-inch steam pipes, which pass through them from end to end. After the impurities have settled the brine is drawn into grainers, which are of about the same size as the settlers, but only 12 to 15 in. deep; they are also heated by steam pipes. The salt forms very rapidly, and is lifted and drained and stored before inspection, as in the kettle process. The character of the salt, especially its fineness, depends less on the character of the brine than on the care and rapidity with which the evaporation has been conducted. The practice called “cutting the grain,” i. e., adding to the boiling brine traces of glue, resin, soap, &c., has been known and employed for generations; but its use is condemned by the best manufacturers, as it requires very great care to prevent the salt from being injured for dairy and other purposes for which fine salt is most used. Salt of the very finest quality is now manufactured at Onondaga, by the Ohio and Kanawha salt companies, and in Michigan.—Uses and Statistics. Salt is the only mineral substance universally employed as an article of food by man and the higher orders of animals. Besides its direct consumption as food, enormous quantities are needed for preserving meats and fish, much is consumed for agricultural purposes and given to cattle and sheep, and a very large amount is used in chemical operations, particularly in the manufacture of soda. This last process alone takes about 48,000 tons annually in France, and a single establishment near Glasgow has used 26,000 tons for the past 20 years. The proportionate consumption of salt in different countries is very variable. In the United States it is estimated at about 50 lbs. annually for each person, in Great Britain at 22, in France at 15 lbs. Animals and many plants will not thrive when totally deprived of salt, though too much acts as a poison. Certain plants which grow at the seaside depend upon it, and are also found inland in the neighborhood of salt mines and lakes. It is employed as a remedy for dyspepsia, and a spoonful of dry salt will sometimes check hæmorrhage of the lungs or hæmorrhage from other causes. In small doses it acts as a stimulant tonic, and in larger ones as a purgative and emetic. It has also been used with good effect in intermittent fever. It is a necessary stimulus in health, quickly passing into the blood and escaping by the kidneys. Its inordinate use induces plethora, increasing the weight and strength of the body. It is sometimes applied as a fomentation in sprains and bruises. Salt-water baths, natural or artificial, are considered stimulating and tonic. Salt is alluded to in many passages of the Bible. All sacrifices offered in the temple were seasoned with it; newborn children were rubbed with it; it is mentioned as one of the things most necessary to life; it is used as a symbol of perpetuity and incorruption, of hospitality (as it still is in the East), and finally of barrenness and sterility, as in sowing the site of a destroyed city with salt. From its necessity salt has in almost all countries been a favorite subject of taxation, and important political results have sometimes arisen from the extortions practised by the collectors, of which the histories of France and Hindostan furnish examples. In England the excise on salt has long been repealed. In the United States, the states most largely engaged in the manufacture of salt appoint an inspector whose duty is to inspect the salt and brand the packages as first or second quality, as it may have been carefully or carelessly prepared. To support this system of inspection a light tax is levied on all the salt produced. In Michigan the tax is three mills per bushel; in New York it is one cent a bushel, which however pays, in addition to inspectors' salary, the expenses incident to running the wells.—It would be impossible to gather trustworthy statistics of the consumption of salt throughout the world. In 1790 very little was produced in the United States, and 2,337,920 bushels were imported; in 1825 the value of the production was more than $1,500,000, and the importation was 4,574,202 bushels; in 1850 the production was 9,763,840 bushels; in 1860, 12,717,193 bushels were produced and 14,094,227 bushels imported; in 1870 the production was 17,606,105 bushels. At present (1875), while our total production has fallen off to some extent, our imports have increased, particularly from Canada, and our total yearly consumption is probably not far from 30,000,000 bushels.

  1. The carbonates are mainly of lime, except in the Holston rock salt, which contains magnesia only. The brines of Nauheim, Onondaga. Kanawha, and many others, as well as sea water and that of the Dead sea, contain traces of bromides and iodides. The dry residue of sea water from the Mediterranean contains 1.47 per cent. of bromide of sodium.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Sulphate of magnesia only.
  3. 3.0 3.1 3.2 Sulphate of soda only.
  4. Sulphate of alumina.
  5. Silicate of soda.