Animal Manures—Their relative value and mode of Action—Difference between Animal and Vegetable Manures—Cause of this difference—Mineral Manures —Nitrates of Potash and Soda—Sulphate of Soda, Gypsum, Chalk, and Quicklime—Chemical action of these Manures—Artificial Manures—Burning and Irrigation of the Soil—Planting and laying down to grass. The animal substances employed as manure consist chiefly of the flesh, blood, bones, horns, and hair of animals, of fish—which in some places are found in sufficient quantity to be laid upon the land—and of the solid and liquid excrements of animals and birds. SECTION I.—OF UNDIGESTED ANIMAL MANURES. Animal substances, in general, act more powerfully as manures than vegetable substances—it is only the seeds of plants which can at all compare with them in efficacy. The _flesh_ of animals is rarely used as a manure, except in the case of dead horses, or cattle which cannot be used for food. Fish is chiefly applied in the form of the refuse of the herring and pilchard fisheries, though occasionally such shoals of sprats, herrings, and even mackerel, have been caught on our shores, as to make it necessary to employ them as manure. These recent animal substances are found to be too _strong_ when applied directly to the land; they are generally, therefore, made into a compost, with a large quantity of soil. Five barrels of fish, or fish refuse, made into twenty loads of compost, will be sufficient for an acre. The refuse of fish oils,—of the fat of animals that has been melted for the extraction of the tallow—of skins that have been boiled for the manufacture of glue—horns, hair, wool (woollen rags), and all similar substances, when made into composts, exercise, in proportion to their weight, a much greater influence upon vegetation than any of the more abundant forms of vegetable matter. Even the bodies of insects are in many parts of the world important manures of the soil. In warm climates, a handful of soil sometimes seems almost half made up of the wings and skeletons of dead insects—the peasant in Hungary and Carinthia occasionally collects as many as thirty cart-loads of dead marsh flies in a single year;—and in the richer soils of France and England, where worms and other insects abound, the presence of their remains in the soil must also aid its natural productiveness.