1315. Gypsum. Besides being used in the forms of lime and carbonate of lime, calcareous matter is applied as manure in other combinations. One of these bodies is gypsum, or sulphate of lime. This substance consists of sulphuric acid (the same body that exists combined with water in oil of vitriol) and lime; and when dry, it is composed of forty-two parts of lime and fifty-eight parts of sulphuric acid. Common gypsum, or selenite, such as that found at Shotover Hill, near Oxford, contains, besides sulphuric acid and lime, a considerable quantity of water; and its composition may be thus expressed: sulphuric acid forty-nine parts; lime thirty-six parts; water fifteen parts in a hundred.