The hard insensible substance of which the frame or skeleton of animal bodies is formed. Although the proportion of the ingredients vary in the bones of different animals, as also in different parts of the same animal, the general constituents of bones are as follows: gelatin or jelly, soluble in hot but not in cold water; fat, separable by boiling, when it rises to the top of the water, and becomes concrete in cooling; phosphate of lime in large quantity; a little sulphate and carbonate of lime; and a cartilaginous substance retaining the form of the bone after every thing else has been extracted, by boiling and by acids. The uses of bones in the arts are very numerous. Both in their natural state and dyed, they are made into knife handles and various articles of turnery ware. They are extensively used in the manufacture of ammonia, the refuse forming bone black; or calcined to whiteness in the open air, they form bone ash, which see. They are also employed in the preparation of milky glasses and porcelains, for the rectification of volatile oils, and in the preparation of glue; and recently in France, large quantities of gelatin have been extracted from bones, which has been subsequently made into soups for hospitals, soldiers, and restaurateurs.

The process is as follows: the bones are first broken into small pieces, and then thrown into a kettle of boiling water, and boiled for a quarter of an hour. When this has become cold, a quantity of fat, amounting in some instances to nearly a fourth of the weight of the bones, is found at the surface of the liquor,and is applicable to many useful purposes. After this, the bones are ground, and boiled in eight or ten times their weight of water, until about one half is wasted, when a very nutritious jelly is obtained. M. Darcet recommends, instead of grinding the bones, which is a work of great labour, to treat them with dilute muriatic acid, which dissolves the salts of lime, leaving the gelatin untouched, and retaining the form of the bones; this is afterwards to be repeatedly washed in clear cold water to free it from all taste of the acid, and then if not required for immediate use, to be thoroughly dried by long exposure to a gentle heat, after which it is little affected by the atmosphere, and will keep for a great length of time. It should be observed, that the bones should not be boiled in copper vessels, as gelatin quickly attacks that metal.

Bones are likewise extensively used in agriculture as a manure, when reduced to a coarse powder; and large quantities are collected for this purpose from various parts of the kingdom, as well as from abroad, and sent to Yorkshire, where most of the bone mills are established, to be ground. The annexed, Fig. 1, represents a side elevation of a bone mill of an approved construction, a a is one of the side frames, b the driving shaft carrying a pinion c, which turns the wheels d to the axis e, and the wheel / upon the axis g; h i are a pair of fluted rollers fixed to their respective shafts e and k, and turning in contrary directions by the action of the two wheels l and m, also affixed to the same shafts; n and o are another pair of rollers affixed to the shafts q and p respectively, and likewise turned in contrary directions by a pair of wheels upon the same axes. These rollers are composed of a series of wrought iron discs, with teeth resembling those of a ratchet-wheel, and fixed up the shaft, with a plain disc of smaller diameter interposed between each pair of the toothed disc, as shewn in Fig. 2, and so arranged that the toothed discs on one shaft shall face the plain discs on the other.

The most valuable part of the bones is first removed by a circular saw, and set apart for the uses of turners and others; the joints and refuse are then put into the hopper q, and descending upon the rollers hi, are crushed, and fall into the hopper r, whence they pass between the rollers l m, where they are reduced to a coarse powder, which is conducted by the shute s (in dotted lines) to the receiver. To prevent the teeth of the rollers being broken by any excessive resistance, the plummer blocks, which support the shafts k and p, are not fixed to the side frame, but are retained in their places by pins passing through chase mortises in the frames, allowing the blocks to slide along the frame, and the rollers are kept in contact by means of weighted levers w a, pressing upon short studs y z, attached to the plummer blocks, which carry the shafts k p.

Fig. 2.

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