1. That animal substances which, like flesh and blood, contain much water, decay rapidly, and are fitted to operate _immediately_ and powerfully upon vegetation, but are only temporary or evanescent in their action. 2. That when dry, as in horn, hair, and wool, they decompose, and consequently act more slowly, and continue to manifest an influence, it may be, for several seasons. 3. That bones, acting like horn, in so far as their animal matter is concerned, and, like it, for a number of seasons, more or less, according as they have been more or less finely crushed—may ameliorate the soil by their earthy matter for a still longer period—permanently improving the condition and adding to the natural capabilities of the land. SECTION II.—OF DIGESTED ANIMAL MANURES. Practical men have long been of opinion that the digestion of food, either animal or vegetable,—the passing of it through the bodies of animals,—enriches its fertilizing power, weight for weight, when added to the land. Hence, in causing animals to eat up as much of the vegetable productions of the farm as possible, it is supposed that not only is so much food saved, but that the value of the remainder in fertilizing the land is greatly increased. In a subsequent section we shall see how far theory serves to throw light upon these opinions. (See Section IV., p. 182 to 186.) I. LIQUID EXCRETIONS. The digested animal substances usually employed as manures are, the urine of the cow and the sheep, the solid excrements of the horse, the cow, the sheep, and the pig, the droppings of pigeons and other birds, and night-soil. The liquid manures act chiefly through the saline substances they hold in solution, while the solid manures contain also insoluble matters, which decay slowly in the soil, and there become useful only after a time. The former, therefore, will influence vegetation more powerfully at first; the action of the latter will be less evident, but will continue to operate for a much longer period. _Urine._—Human urine consists, in 1000 parts, of Water, 932 _Urea_, and other organic matters containing nitrogen, 49 _Phosphates_ of ammonia, lime, soda, and magnesia, 6 _Sulphates_ of soda and ammonia, 7 Sal ammoniac and common salt, 6 ---- 1000