[048] Nitrate of Potash.—This salt occurs in most of the caves in the western states and territories. It is found in efflorescences and incrustations frequently combined with nitrate of lime. Its colour is grayish or yellowish white. The manufacture of nitre, in the numerous caves in Kentucky, is conducted as follows: The earths containing the nitrates of lime and potash are lixiviated; the lixivium is afterwards passed through the ashes of wood, by the alkali of which the nitrate of lime is decomposed. If the earths, after having been lixiviated, are replaced in the caves, they again become impregnated with the same salts.
One bushel of earth commonly yields from one to four pounds of nitre. The process by which nature supplies the consumption of this important article has not yet been discovered.
Muriate of Soda.—In the United States, common salt has been usually found in solution combined with the sulphates of lime, magnesia, and soda, and with sulphuretted hydrogen gas. The springs yielding the greatest quantity of salt, are those of the Kenhawa, and Little Sandy rivers, the United States' Salines near Shawaneetown, Illinois, Boon's Saline, near Franklin, Missouri, and Lockhart's on the Le Mine river.
The Kenhawa salt-works supply about thirty thousand bushels of salt per annum. The rocks about these springs belong to the secondary formation, and are limestone, variegated sandstone, and bituminous shale: we were informed that two hundred and fifty gallons of this water yield one bushel of salt. At the Salines of the Little Sandy, ten thousand bushels are manufactured yearly. The waters, like those of the Kenhawa, hold in solution muriate and sulphate of soda, sulphate of lime, and probably a small portion of sulphate of magnesia. Limestone and sandstone are the only rocks to be met with in the neighbourhood. The United States' salines, near Shawaneetown, produce at present about a hundred and thirty thousand bushels of salt per annum; they formerly yielded more than two hundred thousand in the same time. There are now seven furnaces in operation: the water is procured from three wells, two of which are rented by Major I. Taylor. At these works the salt water formerly issued from the earth at the surface. A well of sixteen feet deep brought the workmen to a spring, which now discharges sixteen gallons of water per minute. Two hundred and fifty gallons yield fifty pounds of salt. About one thousand yards to the east of this well is a basin, or hollow, one hundred and thirty-five feet in diameter. The soil in and about it is intimately blended with fragments of earthen ware.
In the middle of this basin a well has been sunk, which affords a more concentrated brine than that before mentioned; one hundred and ten gallons yielding fifty pounds of salt.
In digging this well, the first fourteen feet was through a light earth mixed with ashes and fragments of earthen ware: the remaining fourteen through a bed of clay, deeply coloured with oxyde of iron, and containing fragments of pottery. The clay has something the appearance of having been subjected to the action of fire. At the eastern side of the basin appears to have been a drain for the purpose of conveying away the superabundant water. In this drain, about four feet below the surface of the earth, is a layer of charcoal about six inches deep. The stones in the vicinity appear as if they had been burnt. Four miles west of this point, a well has been sunk sixty feet through the following beds.
First—— twenty feet of tenacious blue clay, at the bottom of which they came to a small spring of salt water.
Second—— another bed of clay, of a similar character, twenty-five feet thick.
Third—— a bed of quicksand, about ten feet deep; in which they met with a large vein of salt water.
Bones of the mammoth, and other animals, were found both in the clay and sand. The original reservation at these salines comprised ninety-two thousand one hundred and sixty acres of woodland, and was transferred from the United States to the state of Illinois, at the time of the admission of the latter into the union. The rents amount to ten thousand dollars per annum.