cannot remove the lime. Several forms of furnace have been contrived in England to effect this purpose; and retorts are used which hold 50 lbs. of charcoal, and in which the reburning is completed in 15 or 20 minutes.—Besides extracting the color of fluids, animal charcoal takes away the bitter principle from bitter infusions, and iodine also from its solutions; and it is found by Graham that various inorganic substances are abstracted from their solutions, as lime from lime water, and metallic oxides, as lead, from solution in water. Bone black is also used to extract from spirits distilled from grain the volatile poisonous oil, called fusel oil, which gives to the liquors a disagreeable taste. It is also a disinfecting agent.—For chemical and pharmaceutical purposes, bone black requires to be purified, that is, freed from the phosphate and carbonate of lime which constitute its principal part. Dilute hydrochloric acid is used to dissolve these out, and the residue, being well washed, is pure animal carbon. It is used to absorb the active principles of plants from their boiling infusions. The charcoal, after being well washed and dried, is mixed with boiling alcohol, to which it imparts the principle it has absorbed from the vegetable infusion, and an alcoholic extract is obtained. The alcohol then may be distilled off, and the pure substance recovered. Quinia, strychnia, and many other vegetable principles, are thus procured.—The refuse animal black of the sugar refiner is largely used as a manure, and in the manufacture of phosphorus and of baking powders. From the investigations of M. A. de Romanet, it appears that, in old soils exhausted of humus, it produces no effect, having none of this substance to restore to the soil. But it gives out the ammonia it had taken up in the sirups, and neutralizes the bitter and acid principles of healthy or new soils; the phosphates it contains are also rendered soluble in water, and are thus furnished to grains requiring them.
BONE CAVES. In many natural excavations, both in the old and the new world, mostly in the secondary limestone strata, the result of fracture of the earth's crust, of chemical action of acid waters, of erosion by powerful currents, and of slow disintegration by the elements, have been found the bones of extinct post-tertiary mammals, mingled sometimes with the works and bones of man. The most celebrated of these caves in Europe are near Kirkdale, England, 25 m. N.N.E. of York, fully explored by Dr. Buckland; at Bristol; Kent's cave, near Torquay; in the valley of the Dordogne, France, especially those of Moustier and Cro-Magnon, described by Christy and Lartet; and at Gailenreuth in Bavaria. There are many others in Belgium, near Liége; in Sicily, at Gibraltar, in Mexico, in several parts of the United States, and in Brazil. These caves may consist of several chambers at different levels, and show on their walls the erosive action of water, and at the bottom and top various deposits of stalagmite and stalactite from the infiltration of lime-bearing waters. Under this lime floor ancient bones have been discovered, mingled, both as to size and species, in the most indiscriminate manner; they are often rolled, as if from the action of floods, sometimes fissured, but often unchanged. The bones most abundantly found are those of the great carnivora of the quaternary period, the bear, hyæna, lion, &c.; with those of the great pachyderms, as the mammoth and the rhinoceros; and of many herbivora and rodents. The English caves were mostly occupied by hyænas, while those of the continent were chiefly caves of bears. At Kirkdale Dr. Buckland found the remains of at least 75 hyænas, of the extinct or cave species, mixed with those of the extinct pachyderms, carnivora, ruminants, and rodents; from which he believed that the hyænas dragged the carcasses there and fed upon them, cracking their bones with the marks of their teeth peculiar to this animal, and leaving behind them their fossil fæces. In Gailenreuth have been found the bones of the cave bear, of at least 800 individuals. Caves containing bones of post-tertiary mammals are rare in North America; but in those of Brazil, explored by Dr. Lund, remains of gigantic rodents, pachyderms, and edentates were found, especially of the extinct megatherioids. The bones found in the caverns have a uniform appearance over large areas of country, and evidently belong to the geological period intermediate between the tertiary and the present epochs. Though some of these caves owe their remains to the fact that they were the dens of hyænas and bears, or were the retreats of sick and wounded animals, there can be no doubt that most of their contents have been brought to the caves by temporary torrents of water independent of marine action; the bones could not have come from a great distance, as they belong to the then existing animals of the region, and are the same as those met with in external transported sediments. Remains of man and of his works have been found mingled with the bones of the above post-tertiary extinct mammals in the caves of Europe, and especially of southern France by Messrs. Christy and Lartet, seeming to place it beyond doubt that man began his existence at this remote epoch. The implements found are invariably those of the early stone age, and the bones never those of the domestic animals afterward subjugated by man.—See Archæology, and the works of Dr. Buckland, Constant-Prévost, Lyell, and the Reliquiæ Aquitanicæ of Christy and Lartet.
BONE DUST, bones crushed and ground to dust for manure. The finer the dust the more rapid is its action ; the coarser the particles, the longer is their effect slowly given out. This substance is beneficial to the growth of plants from its affording them several of the constituents they require. The following analysis of dry ox bones is by Berzelius:
