Near to the saltern is a cistern either of wood, brick, or clay, and covered with a shed. This cistern is placed at such a height that the Water can run out of it into the pans. Into that cistern the sea water is raised by pumping machinery from a well into which the water is conveyed by a pipe from a pool or.lump formed in the sand.
When the sea water in the cistern has settled and deposited its mud and sand, it flows into the salt pan, beneath ivhich, as.soon as it is full, a strong fire is lighted in the furnace. When the water is lukewarm, it is in some places clarified by mixing the white of three or four eggs, with two or three gallons of sea water, and pouring the mixture into the salt pan. The blood of sheep or oxen being sometimes used for the same purpose.
As the water approaches to the boiling heat, the frothy scum or scratch which appears on its surface is collected into four small pans called scratch pans, one of which is at each corner of the boiler. The water now becomes perfectly clear, and after four hours boil ing, crystals are seen forming on its surface. The pan is now filled to the top with fresh sea water from the cistern; the eggs or bullock's blood being used as be fore, and the black scum removed into the scratch pans which have been previously emptied of their white powder, a sort of calcareous earth which they contain ed. This second filling of the pan is boiled down like the first, and the pan is filled a third and a fourth time, and boiled in the same manner till the crystals begin to shoot. At this period of the fourth boiling, the fire is allowed to become low, so that the brine only re mains, in which state it is kept for ten or twelve hours, while the salt is granulating or falling in grains or small crystals to Old bottom of the pan. When tho water is nearly drawn off by evaporation, the salt, which is nearly in a dry state at the bottom of the pan, is raked together into one or two heaps till the brine drains from it, when it is conveyed in barrows to the store-house. In some salt works the pans are filled up seven times in place of four, with fresh sea water, in which case the salt is drawn out only once every two days in place of every day, as in the common method.
From a pan of 1300 gallons from 15 to 20 bushels of salt of 561bs. each, are obtained every day. In the store-house the salt is laid into drabs or wooden troughs, with shelving bottoms, and a sliding board at the lower end, so as to allow the brine to run off. In three or four days the salt is generally quite dry.
2. Manufacture of Salt from Brine Springs, The method of manufacturing salt from brine springs differs very little from that of manufacturing it from sea water. In our article on CHESHIRE) we have given a brief account of the method and of the brine springs in that county; and in our article FRANCE, we have described the methods used at Salim.
The following account of the American brine springs which we have abridged from Dr. Rensselaer's Essay on Salt, recently published, will be interesting to the reader.
" Illinois abounds with salt. The most important work is near Shawneetown, where there are now seven furnaces in operation to extract salt from the water of three wells, which used to flow on the surface at the rate of sixteen gallons per minute. These works, which have produced 200,000 bushels in a year, at present yield 150,000 bushels, worth about 70 cents on the spot. Two hundred and fifty gallons of brine yield 501bs. of salt. Near one of the wells is a basin-shaped cavity of about 400 feet in circumference, the soil in and about which is intimately blended with fragments of earthenware. In the centre of it a well has been sunk, which affords a more concentrated brine, 110 gallons yielding 50Ibs. of salt. In digging this well, the first fourteen feet were a slight earth mixed with ashes and fragments of earthenware; the remaining fourteen were through a bed of clay, deeply coloured with oxide of iron, and containing fragments of pot tery. The clay has something of the appearance of having been subjected to the action of fire. In a drain, which seems to have answered the purpose of carrying away superabundant water, is a layer of charcoal, six inches deep, and four feet below the surface. The stones in the vicinity seemed as if they had been burnt.