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the soil, and occasion a vigorous vegetation. Blood and urineare highly concocted animal fluids, in which salts are generated,and they are subject to a very rapid putrefaction. When pour-ed fresh and unmixed on the ground, they kill growing plants;but if diluted with a large proportion of water, and agitated init, they encourage vegetation ; or, when they ferment anew, pu-trefaction ensues: their salts are decomposed: and as they notonly contain vegetable nourishment in solution, but are powerfulsolvents of it in other bodies with which they are mixed, they arevery valuable as manure.
Although it seemed requisite thus rapidly to recognize theVarious properties of different animal substances, considered asmanure, there is but a small part of them applied directly tothat purpose, being in request for various others, for which theyare of higher value. But there are two other substances notdescribed, differing somewhat from all the rest, and greatly fromeach other. Bones are a compound of a most imperishable kind;burnt bones being frequently found, the organization of whichis still preserved entire since the time that the Romans possessedthis island. They are now known to be a compound of phos-phoric acid and lime (phosphate of lime). Mr Kirwan recom-mends bone dust as an appropriate manure for wheat, in whichsome phosphorus is found ; * and Mr Chatterton had a succes-sion of rich crops by applying it to a field. § But it does notappear that a combination so unperishable should yield that in-gredient to a crop of wheat growing over it, or that this sub-stance, after the oil and mucilage contained in it is exhausted,can serve any other purpose than as an ingredient in the soil.Mr Chatterton was probably, therefore, more obliged to the con-tents of the bones, than to the bones themselves. Dung is part-ly of the substance of the animal which voids it, and partly someof its food undigested and little altered : of course the dung ofgraminivorous animals, which is one of the most considerablearticles of manure, is partly animal, partly vegetable matter,and must be more fully considered when we come to CompositeManure.
III. Vegetable Manure.
Vegetables are either arboreous or herbaceous. The arbo- .reous are such as continue for a series of years to increase in sizeby annual enlargements and elongations. Their principles arethus formed into more durable combinations, and do not quicklyreturn to nourish a new race of vegetable beings. Some of themare however occasionally brought to that use. The shavings ofboard, small chips, and saw-dust, macerated for a time in putridwater, gradually decompose in the soil, and become tire food of
§ Communications to the Board, p. 121'