Salt deposit

“ The limestone that had been carried in and deposited on the lake bottom then became the new ground surface.
Salts left by the evaporation of water were also deposited on the lake bottom. A deposit of this type can now be seen near Camp Verde. Although the formation is principally sodium carbonate, sodium chloride (common table salt) and sodium sulphate are also found. For many centuries early Indians mined salt deposits in this locality and a few years ago a deposit of sodium sulphate near Camp Verde was worked commercially. ”

“ When a sufficiently thick crystalline deposit has been formed at the bottom of the secondary ponds, workmen, starting at the centre, scrape the bottoms, working outward spirally and finishing at the corner of the pond, where the coarse crystalline product is collected and allowed to drain. When drained and dried, the salt is ready for transfer to the market. ”

“ In Italy most of the salt is made by solar evaporation. The salt grounds, which occupy extensive areas, are14 furnished with reservoirs for the preparation of the sea-water by saturation and for the deposit of salt. The former are known as condensers and the latter as crystallizing beds, and in both the work is carried on by solar evaporation only. Every salt-ground, or salt-garden, as it is called, has a feeding channel for the inflow of sea-water, a drainage channel, and a network of internal channels at low and high levels, as are required for immission or drainage purposes. ”

“ 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. ”

“ Rock salt forms the most common and practical source of supply. It is found in all parts of the world and reasonably near the surface. The deposit is said to be what is left of ancient salt seas. In the United States the largest deposits of salt are found in the states of Michigan, New York, Ohio, Utah, Louisiana, Kansas, Texas and California. The above-mentioned states are the largest producers of salt in this country.
Salt Heaters and Filters
One of the largest sources of salt supply in Europe is at Wielizka in Poland. ”

“ SALT. Geological Position of Rock Salt—Mines of Northwich—Their immense Excavations—Droitwich and Stoke—Wieliczka—Berchtesgaden and Reichenhall—Admirable Machinery—Stassfurt—Processes employed in the Manufacture of Salt—Origin of Rock-salt Deposits.
Common salt is so necessary to man, and of such vast importance to the manufacturer and agriculturist, that the processes by which it is obtained are justly reckoned among the chief branches of industry.
In many of the warmer countries of the globe it is procured simply by the evaporation of sea-water in shallow lagoons ”

“ The story of the exploitation of the top and bottom beds is one that is soon told. The top bed was worked until the mines began to fall in and the subsequent breaking in of fresh water converted the old workings into brine reservoirs. In 1779, the discovery of the lower bed of rock-salt at Lawton prompted the owners of the Marston Mine at Northwich to sink below the top bed in which they were working, and, in 1781, a trial shaft which was sunk from the top mine by means of a horse gin, demonstrated the existence of the bottom deposit in that district. ”

“ And so construed, it is said, even by the decision in this case, the grant of 110,000 acres will be increased 40,000 acres, and as the demurrer concedes the deposit of salt is from 4 to 8 feet thick, there will be the further increase of two or three million tons of salt, worth in the aggregate an almost fabulous sum. ”

“ Where the salt deposits are composed of a mineral that is white, odourless, and practically pure, as in the Wieliezka system and the mines of Rumania, and particularly if labour is abundant and cheap, and the industry is a monopoly of the State, rock-salt mining will always hold its own. ”

“ It is true that experiments were made with the sizes and arrangement of the pans, that coal replaced wood and straw as fuel, that the locomotive superseded the wain as a means of transporting salt from the works to the markets, and that pumps were employed instead of buckets to raise the brine and deposit it in the cisterns which supplied the pans ”

“ Common salt constitutes the mineral halite, the composition of which is sodium chloride. It is rarely found perfectly pure in nature, but is commonly mixed with other saline materials, such as gypsum and anhydrite, and occasionally with salts of potassium and magnesium. The general grade of rock-salt deposits, where not admixed with clay, is perhaps 96 to 99 per cent of sodium chloride. ”

“ The difficulty of explaining how the salt in this lake could be renewed to enable the waters to go on depositing for a geologic age is recognized, but it is no greater than that which is presented by scores of existing salt lakes out of which thousands of tons of salt are taken annually without causing any apparent diminution in the salt which forms year by year. And when it is considered that, in a lake having a probable area of from 500 to 1,000 square miles, the known salt deposits do not occupy 50 square miles, and in many portions contain 50 per cent. ”

“ The deposits, which are found at a considerable height above sea-level, are of great but undefined magnitude, as the lowest strata has been bored through for a thickness of 72 feet, without penetrating the formation. The rock salt here was acknowledged to be purer than any previously encountered in Cheshire, and the brine derived therefrom, containing 26·100 chloride sodium by weight, yields on evaporation an exceptionally high class of white salt. ”

“ Some of the lakes of the Great Basin are dense brines from which various substances are being precipitated. The economic importance of these natural reservoirs of brine and of various soda salts is great, and will become more and more important as transportation facilities increase. Great Salt Lake, it has been estimated, contains 400,000,000 tons of common salt and 30,000,000 tons of sodium sulphate in solution. During the past ten years about 40,000 tons of common salt have been harvested from it annually. ”

“ But when the saturated brine is pumped up and its place is taken with a new supply of water which collects its tribute from the salt strata, and that water, in its turn, is raised, to be replaced by more, and when it is known that each 100 tons of water that traverses the salt-bed to the pumps carries away with it 25 tons of solid earth, the work of destruction that is continually going on is explained. ”

“ Even in this country, when the old open-pan system of evaporating salt from brine produced only two tons of salt for the consumption of a ton of fuel, rock-salt could be raised, purified, and marketed in competition with white salt, but the modern boiling processes have effected such substantial improvements and consequent economical advantages, that the rock-salt industry appears to be doomed to decay. ”

“ The only assumption required to enable us to explain a great thickness of salt in such as area is, the continuance, for an indefinite period, of a subsiding movement, the country preserving all the time a general approach to horizontality. Pure salt could only be formed in the central parts of basins, where no sand could be drifted by the wind, or sediment be brought by currents. Should the sinking of the ground be accelerated, so as to let in the sea freely, and deepen the water, a temporary suspension of the precipitation of salt would be the only result. ”

“ Nearly 78 per cent of the dissolved matter is common salt. The principal other constituents in solution are chloride and sulphate of magnesia, and the sulphates of lime and potash. All other dissolved mineral substances together make up less than one per cent of the total. It has been estimated that if all the dissolved mineral matter should be brought together, it would form a layer 175 feet thick over the whole sea bottom. The salts of the sea have been mostly supplied by the rivers, which in turn have derived them from the disintegration and chemical decay of the rocks. ”

“ 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. ”

“ About six hundred thousand quintals of salt are dug annually out of the mines of Cracow. The worst and cheapest is called green salt, from its greenish color, occasioned by a heterogenous mixture of a grayish mineral, or clay, and entirely consists of salt crystals of different dimensions. A finer sort is dug out in large blocks; and the third kind is the sal gemmæ, or crystal salt, which is found in small pieces interspersed in the rock, and, when detached from it, breaks into cubes of rectangular prisms. ”

“ The herbivorous animals were equally dependent upon salt, and, finding it in only infinitesimal quantities in the grasses upon which they fed, instinct directed them to the sea swamp pasturage and to the outcropping salt deposits. So long as man’s diet consisted of uncooked foods, his fresh meat provided him with a sufficiency of salt, but directly he employed a cook-pot in the preparation of his food, the boiling processes denuded it of 70 per cent. ”

“ The pumping from the reservoirs formed by the flooding of the old mines does not empty these huge receptacles, as the place of the brine is continuously retaken by fresh water, which naturally gravitates to these centres and proceeds to dissolve and take up its quota of rock-salt. When a subsidence occurs on the site of these old workings it is of the most destructive nature, and as all the top-rock mines were in the neighbourhood of streams and brooks, the surface waters flow into the cavity until it is filled to the level of the earth and allows the streams to pursue their proper course. ”

“ In warm humid regions chemical decay of the rocks is the conspicuous feature; in equally warm arid lands mechanical disintegration is carried to an extreme, without the removal of the more soluble constituents. In fact, concentration of saline matter, notably common salt, sodium sulphate, gypsum, etc., is one of the functions, so to speak, of arid climates, when the requisite evaporation basins are present. Among the important industries of the Great Basin region is the gathering and purifying of the various salts contained in the existing water bodies and in the basins of desiccated lakes. ”

“ This is entirely independent of the rock-salt, which, at a low estimate, equals 120,000 tons per annum, or, say, 75,000 cubic yds., or 15·5 acres of 1 yd. thick.
In these calculations no allowance has been made for wastage, and this is very large. During the year every pan requires picking from six to twelve times, the stoved oftener than the common. This necessitates the pan being swept out and an enormous quantity of brine wasted. Besides this, the pan scale contains a large percentage of salt. Again, in drawing the salt out of the pans a large quantity of brine is wasted. ”

“ They have, in fact, to make the best of a condition of things from which there is absolutely no escape. The effects described are produced, not indeed by any sudden catastrophe, but by a slow, though equally effective process of subsidence, which may be detected in continuous operation over nearly the whole area of the Cheshire salt field, and which will continue to operate so long as the earth yields its vast stores of salt for human consumption. ”

“ In most rock-salt mines such specimens are regarded as curiosities, but in the deposits of Nevada and of Wieliezka, in Hungary (where the salt, containing 100 per cent. NaCl, is the purest in the world) , large masses of quite transparent salt are encountered. The white opaque mass which the ordinary person is accustomed to think of as rock-salt, is the purified product2 of commerce. The colour of sea-water is affected by its percentage of salt, the colour changing from blue to green as the quantity of salt decreases ”

“ The State of New York controls the wells and pumps the brine to supply the evaporating works, which are private establishments, a royalty of one cent per bushel being charged. The main impurity that has to be driven out of the brine 356 is sulphate of lime, and the finer product has a high reputation, the "Onondaga Factory-Filled Salt" being greatly esteemed. The salt wells were known to the Indians, and the French Jesuit missionaries found them as early as 1650, taking salt back to Canada. ”

“ In each gallon of river or rain water dissolve about six ounces of sea-salt, either by stirring it or suspending it in the water in a linen or muslin bag. It dissolves as readily in cold as in hot water. Sea-salt is produced by evaporation of sea-water. Common salt is sometimes supplied in place of it; but the genuine sea-salt, manufactured by well-known firms, which can be procured of any grocer or of most chemists, is specially prepared to enable persons to have a salt-water bath at home. ”