George and Francis Moult (the latter was, no doubt, the chymist who kept the shop in Watling Street) in about the year 1700 found a more abundant supply of the popular salt in a spring at Shooter’s Hill, where it is recorded they boiled down as much as 200 barrels of the water in a week, obtaining some 2 cwt. of salt from these. Some time after, a Dr. Hoy discovered a new method of producing an artificial salt which corresponded in all respects with the cathartic salts obtained from Epsom water, and which by reason of the price soon drove the latter out of the market, and caused the Shooter’s Hill works to be closed. It was known that Hoy’s salt was made from sea water, and at first it was alleged to be the sal mirabilis of Glauber, sulphate of soda. But this was disproved, and experiments were carried on at the salt works belonging to Lady Carrington at Portsmouth, and later at Lymington, where the manufacture settled for many years, the source being the residue after salt had been made, called the bittern--salts of magnesium, in fact. This was the principal source of supply, though it was made in many places and under various patents until in 1816 Dr. Henry, of Manchester, took out a patent for the production of sulphate of magnesia from dolomite. It should be mentioned that it was by the examination of Epsom salts that Black was led to his epoch-making discovery of the distinction between the alkaline earths, and also of fixed air, in 1754. In Quincy’s “Dispensatory” (1724), medicinal waters like those of Epsom are described as Aquæ Aluminosæ. It is stated that there are many in England, scarce a county without them. The principal ones about London are at Epsom, Acton, Dulwich, and North-hall. They all “abound with a salt of an aluminous and nitrous nature,” and “greatly deterge the stomach and bowels.” But it is easy to take them too frequently, so that “the salts will too much get into the blood, which by their grossness will gradually be collected in the capillaries and glands to obstruct them and occasion fevers.” After some more advice Quincy adds--