Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/56
Mr. H. Holland on the Cheshire Rock-Salt District.
It may be sufficient here to state a few of the most general and important facts.
The brines met with in this district are very generally formed by the penetration of spring or rain waters to the upper surface of the rock-salt, in passing over which they acquire a degree of strength, modified by several circumstances, which it would be needless to detail. Their average strength, however, appears to be much greater than that of the springs met with in Hungary, Germany, or France. At Winsford, Northwich, Anderton, Lawton, Roughwood, Wheelock, and Middlewich, where all the principal salt works are situated, the brine springs contain between 25 and 26 per cent. of the pure muriate of soda; and in some of the springs at Anderton, the proportion stands as high as 26.566 per cent. a very near approach to the perfect saturation of the brine. The earthy salts held in solution together with the muriate of soda are principally muriate of magnesia and sulphate of lime; the quantity of these varying from per cent. to per cent. in different springs. The brine being pumped out of the pits, is first conveyed into large reservoirs, and afterwards drawn off as it is wanted, into evaporating pans, made of wrought iron. Here heat is applied in a degree determined by the nature of the salt intended to be manufactured, and various additions are made to the brine, with a view either to assist the crystallization of the muriate of soda, or to promote the separation of the earthy salts. The latter exist in a very small proportion in the manufactured salt, and cannot be supposed in any degree to affect the uses to which it is applied.  The importance of the Cheshire
- In reference to the chemical character of the different varieties of salt, an excellent paper by my friend Dr. Henry will be found in the Philosophical Transactions for the year 1810. Part I.