BONES have been of late years very exten sively used as a manure, especially on poor and dry sands and gravels. When crushed and used judiciously, the advantage of bones as a manure, in distant and uncultivated spots, where the carriage of common stable or yard manure would have been too expensive, and where it could not be made for want of food for cattle, is incalculable. By means of bones large tracts of barren sands and heaths have been converted into fertile fields.
The bruising or grinding of bones has be come a distinct business, and they may be bought in London and at the principal ports ready to put upon the land. They are broken into different sizes, and are accordingly called inch bones, hay-inch bones and bone-dust. Most of the bones procured from London and the manufacturing towns have undergone the process of boiling, by which the oil and a great part of the gelatine which they contain have been extracted. The German agricul turists instead of using bone-manure on their own land, now export it to England, on ac count of the good price here obtainable. No less than 29,424 tons of foreign bones were imported in 1819.
Bones consist of about one-half animal matter : the rest being phosphates of lime and magnesia, and carbonate of lime. They derive their fertilising property mainly from the phosphate of lime; but in part also from the mechanical texture of the bones, and their power of absorbing and retaining mois ture, which enables the plants to feed on the decomposed gelatine of the bones.
The mode of applying bone manure to the land is either by sowing from twenty to forty bushels of them per acre by the hand broad cast, as is done with corn, and harrowing them in with the seed; or by putting them into the drills by a machine made* for the purpose, which is an addition to the common drilling machine.
The mill which is used to break and grind' bones consists of two iron or steel cylinders, with grooves running round their circumfer ence, the projections being cut so as to form strong teeth. These turn upon one another by means of machinery, so that the teeth of one run in the groove between the teeth of the other. The hones arc put into a hopper, whence they pass between the two cylinders, where they are crashed during the passage. The bones from Germany are sometimes ground before importation, sometimes after wards.
The uses of bones (besides as a manure) are very numerous. Bone-ash is prepared by calcining bones to whiteness, and reducing them to a powder ; it is used for burnt harts horn, and for making cupels. Bone-black, or ivory black, is made by a careful preparation of the soot of clean bones, when burned in a peculiar manner. There are successive stages in the manufacturing uses of bones ; first the bones are boiled, and the grease sold to the candle and soap makers ; then the larger pieces are selected for making knife-handles, &c.; then the best pieces are laid aside for bone-black ; and finally the worst pieces are appropriated as manure. The coarser kind of bone-black is made into animal cluzrcoal, used by sugar refiners ; while the finer kind is em ployed in snaking black paint and colours, inks, dyes, &c.
Bone, as a material for knife handles and other articles, may be dyed red, black, green, purple, yellow, blue, or other colours, by the same dyes as are used for ivory. Bone is easily wrought by the saw and lathe.