_Phospho-Peruvian Guano._--Under this name a kind of superphosphate, which is understood to be made by dissolving a native "rock guano," has recently attracted considerable attention, and is used to a large extent. Its composition is-- Water 9.54 Organic matter 21.38 Biphosphate of lime, equivalent to 25.22 soluble phosphates 16.81 Insoluble phosphates 10.88 Sulphate of lime 37.21 Alkaline salts, containing 1.32 of phosphoric acid, and equivalent to 2.86 soluble phosphates 2.22 Sand 1.81 ------ 100.00 Ammonia, 3.50 It is chiefly distinguished by the large proportion of valuable ingredients it contains, and the care taken to secure uniformity of composition. A variety of substances are sold under the name of nitrophosphate, potato manure, cereal manure, etc. etc., which are all superphosphates, differing only in the proportion of their ingredients, and in the addition of small quantities of alkaline salts, sulphate of magnesia, and other substances, but they present little difference from ordinary superphosphates in their effects. The use of superphosphate has greatly extended of late years, and its consumption has increased in a greatly more rapid ratio than that of guano or any other manure. Ten or twelve years since it was comparatively little known, but it has now come to be used in many cases in which Peruvian guano was formerly employed. It produces a better effect than that manure on light soils, although in general a mixture of the two answers better than either separately. When Peruvian guano is to be applied along with it, the farmer will naturally select a superphosphate made from bone ash, and containing the largest obtainable quantity of soluble phosphates; but when it is to be used alone, it is advisable to take one made from bones, or at all events one containing a considerable quantity of nitrogenous matter or ammonia. The kind to be selected must, however, be greatly dependent on the particular soil, and the situation in which it is to be used.