1198. The presence of calcareous matter in soil may be ascertained by simply pouring any acid on it, and observing if it effervesces freely. Muriatic acid is the best for this purpose. Calcareous soils, magnesian soils, and clays, are, for the most part, softer to the touch than arenaceous soils. To ascertain the quantity of calcareous earth present, dry soil thoroughly, and weigh 100 grains of it, which gradually add to one drachm of muriatic acid diluted with two drachms of water in a phial poised in a balance: the loss of weight will indicate the escape of carbonic acid, which will be 44 per cent. of the quantity of calcareous earth in the soil.