EPSOM, a market town in the county of Surrey, is situated about 14 miles S.W. of London, on a branch of the London and Brighton railway. The town is irregularly built, but contains some handsome new houses. The principal building is the parish church, a Gothic edifice, rebuilt in 1825, the interior of which contains some fine sculptures by Flaxman and Chantrey. Epsom has attained a wide celebrity on account of its mineral springs and its races. The former were discovered about 1618, and for some time after their discovery, the town enjoyed a wonderful degree of prosperity. After the Restoration, it was often visited by Charles IL, and when Queen Anne came to the throne, her husband, Prince George of Denmark, made it his frequent resort. Epsom gradually lost its celebrity as a spa, but the annual races held on its downs have arrested the decay of the town. Races appear to have been established here as early as James I.’s residence at Nonsuch, but they did not assume a permanent character until 1730. The principal races—the Derby and Oaks— are named after one of the earls of Derby, and his seat, the Oaks, which is in the neighbourhood. The latter race was established in 1779, and the former in the following year. The spring races are held on a Thursday and Friday towards the close of April; and the great Epsom meeting takes place on the Tuesday and three following days immediately before Whitsuntide,—the Derby on the Wednesday and the Oaks on the Friday. The grand stand, erected in 1829, is 156 feet wide and 70 feet in depth, consists of three stories, accommodating nearly 5000 spectators, and includes a saloon 108 feet by 34. The population of the civil parish, in 1871 was 6276.

EPSOM SALTS, the magnesioe sulphas of pharmacy, and the epsomite or hair-salt of mineralogical treatises, is an hydrated magnesium sulphate, of the chemical constitution MgSO 4 .7H 2 O, and isomorphous with zinc sulphate (see vol. vi. p. 527), which it resembles in appearance. The salt crystallizes in four-sided, right-rhombic, lustrous, colourless prisms, which in the commercial article are usually acicular in shape. It can be obtained also in crystals of the monoclinic system. It is very soluble, one part dissolving in 0 ’ 79 parts of water at 18∙75° C., and has a bitter, saline, and cooling taste. The salt is prepared on the large scale by several methods, c.<∕., by the treatment of the bittern of salt works with sulphuric acid or ferrous sulphate, by which the magnesium chloride of the liquid is converted into sulphate; by acting on magnesite, the native magnesium carbonate, or on magnesian limestone, with sulphuric acid, preferably, in the case of the latter substance, after the removal of the calcium carbonate by means of hydrochloric acid; and, as in the neighbourhood of Genoa, by the roasting of pyritous serpentine, subsequent exposure to the air and lixiviation, peroxidization of ferrous salts by chlorine, precipitation of ferric oxide by burnt lime or dolomite, and evaporation of of the resultant solution of magnesium sulphate. The mineral waters of Seidlitz, Saidschutz, Piillna, and of other places besides Epsom owe their potency to magnesium sulphate. The salt occurs in fibrous crusts or botryoidal masses in some limestone caves; in gypsum quarries, as a result of the action of the gypsum on magnesian limestone; and in the old workings of mines, where it is produced by the oxidation of pyrites in the presence of magnesium compounds. As a hydragogue ...