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576 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