Page:A tour through the northern counties of England, and the borders of Scotland - Volume I.djvu/78

 seems to be salt rock, which lies usually from one hundred and fifty to two hundred feet under the surface; the first spring is met with about one hundred and ten feet down, after which occurs a stratum of gypsum one hundred or one hundred and thirty feet in thickness; then a brine river of twenty-two inches deep, and finally a bed of salt rock of unknown thickness. In a search for the brine river made a few years since, the successive appearances in the earth were these—mould four feet, marl thirty-two feet, gypsum forty feet, a brine river twenty-two inches, another stratum of gypsum seventy-five feet thick, and then the salt rock. From the brine thus procured, which exceeds all others in strength and purity, is manufactured the Droitwich salt, by the following process:—A small quantity of water being previously poured into the boiling pan, to prevent the brine from burning at the bottom, it is then nearly filled with this strongly impregnated saline liquid; the pans are made of iron, broad, flat, and about fifteen inches deep, and placed over a furnace, with a high and wide chimney above them to assist the evaporation. A small lump of resin being thrown into the brine, to make it granulate, the process of ebullition and evaporation soon takes place; an incrustation of salt is presently formed on the