The rest of the process was to be seen down at the works, so thither we went; not by the way I came, for the foreman, scrambling up the side of the gap, conducted me along the ledge at the top of the burning heap. He walked through the stifling fumes without annoyance, while on me they produced a painful sense of choking, with an impulse to run. Before we had passed, however, he pushed aside a few of the upper pieces, and showed me the dull glow of the fire beneath. Then we had more ledges along the face of the cliff, and now and then to creep and jump; and we crossed an old digging, which looked ugly with its heaps of waste and half-starved patches of grass. All the way extends a course of long wooden gutters, in which the first-run liquor was flowing in a continuous stream to undergo its final treatment--another trial by fire.
Then into a low, darksome shed, where from one end to the other you see nothing but leaden evaporating pans and cisterns, some steaming, and all containing liquor in different states of preparation. That from which the most water has been evaporated--the concentrated solution--has a large cistern to itself, where its tendency to crystallize is assisted by an admixture of liquor containing ammonia in solution, and immediately the alum falls to the bottom in countless crystals. The liquor above them, now become 'mother liquor,' or more familiarly 'mothers,' is drawn off, the crystals are washed clean in water, are again dissolved, and once more boiled, mixed with gallons of mothers remaining from former boilings. When of the required density, the liquor is run off from the pan to the 'roching casks'--great butts rather, big as a sugar hogshead, and taller; and in these is left to cool and crystallize after its manner, from eight to ten days, according to the season. The butts are constructed so as to take to pieces easily, and at the right time the hoops are knocked off, the staves removed, and there on the floor stands a great white cask of alum, solid all over, top, bottom, and sides, except in its centre a quantity of liquor which has not crystallized. This having been drawn off by a hole driven through, the mass is then broken to pieces, and is fit for the market; and for the use of dyers, leather-dressers, druggists, tallow-chandlers; for bakers even, and other crafty traders.