Pillar of salt

Definition and stakes

Portrait of Albert Frederick Calvert Albert Frederick Calvert Salt and the salt industry (1919)

Let it be clearly understood that all commercial salt is produced either from the sea or from rock-salt. Sea-water is evaporated to precipitate its salt either by the heat of the sun or by artificial heat. Rock-salt is mined and refined for market purposes, and it is resolved into brine from which the salt is extracted by solar heat or the process of boiling, but whether the salines are obtained from salt lakes or from natural brine springs, or are prepared by flooding salt deposits with water and pumping it out in the form of fully saturated brine, rock-salt is the foundation for them all.
Source: Gutenberg

Portrait of Albert Frederick Calvert Albert Frederick Calvert Salt and the salt industry (1919)

Particles of chloride of sodium in volcanic ejections were no explanation of the formation of huge deposits of rock-salt, and since it was realized that salt in large quantity can only be obtained from salt water, and that it cannot be got naturally from the sea, it became evident that what man does in isolating tracts of sea-water to produce salt by solar evaporation, must have been practised by nature on an extensive scale in all ages.
Source: Gutenberg

Thomas W. Corbin The Romance of War Inventions

Common salt is a combination of the metal sodium and the gas chlorine. There are many places, of which Cheshire is a notable example, where vast quantities of this salt lie buried in the earth.
Fortunately it is very easily dissolved in water so that if wells be sunk in a salt district the water pumped from them will have much salt in solution in it. This is how the underground deposits are tapped. It is not necessary for men to go down as they do after coal, for the water excavates the salt and brings it to the surface.
Source: Gutenberg

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