IVORY is the bony substance of the teeth of animals, but is applied particularly to the tusks of the elephant. Those of the hippopotamus, wild boar, several phocm, and the horn or tooth of the narwhal, pass by the same name. The tusk of the elephant is of a circular or oval shape, some inches thick at the root, and several feet in length, if full grown. It is hollow for a considerable space from its insertion into the jaw, and always tapers to an obtuse extremity. Most tusks are curved, generally more so in proportion to their sizes for the smallest brought to this country are perfectly straight. Naturalists, however, con ceive that the curvature of the tusk is not a decisive charac teristic of the species of the elephant, but only constitutes a variety. Perhaps this is a point meriting further investi gation ; and it should be attended to, that those called mammoth's tusks, found on the shore of the Icy Sea, are said to be spiral, forming about a volute and a half, through out their length. The size of the hollow is various in pro portion to the tusk. It is of a conical figure, circular or elliptical, commonly corresponding to the exterior outline of the whole ; and, indeed, it is to be observed, that all the lines and layers, observed in a transverse section, have a relation to the external circumference of the tusk. Thus it is probable, that these peculiarities depend on the origi nal conformation of the pulpy nucleus occupying the cavity. In small tusks, the upper part of the hollow is totally lost in the solid, being scarcely perceptible, or forming only a dark shade. In those of larger size, it diminishes to an aperture of a line or less in diameter at its termination on the outside at a short distance from the tip. It is techni cally called the nerve on assuming the latter appearance, and sometimes is encircled by so dark a shade as greatly to injure the ivory. Tusks are most esteemed which have least hollow.
Nothing can be more diversified than the dimensions of the tusks of the elephant, and hence the dealers in ivory distinguish them by names according to their size. If weighing under 14 or 20 pounds, they are called crevelles, or, as the workmen say, scrivelis, many not exceeding a foot in length. None brought from the south-west coast of
India exceed four feet, it is said ; but some of an extraor dinary bulk are obtained in other countries. In Roman history, we read of tusks ten feet long ; and Mr. Pennant speaks of others equally large, brought from the coast of Mozambique, in modem times. Tusks of eight or nine feet long are repeatedly mentioned ; and Hartenfels, in his work on elephants, instances one, of the wonderful length of 14 feet, in the possession of a merchant in Venice. Very large tusks are six, seven, or even nine inches thick, according to Camper, who observes, that one about seven feet nine inches long, nine inches thick, and weighing 208 pounds, belonged to a merchant of Amsterdam. No gene ral conclusions regarding the weight are deducible from the size. Tusks have been known to weigh 325 or 350 pounds. Some fossil tusks are also very ponderous. One is described by Bryene, in the Philosophical Transactions, 136 inches 5 lines long on the exterior of the curve, whose circumference was 18 inches 5 lines at the root on clearing the socket, and which weighed 137 pounds. The largest, found on the shores of the Frozen Ocean during the Rus sian voyage of discovery in 1787, were eight feet seven inches long following the volute, but only four feet and an inch in a straight line, very nearly 18 inches in circumfe rence at the thickest part towards the root, and weighing 115 pounds avoirdupois. Cuvier supposes, that tusks grow during the whole life of the elephant ; and as the extre mity is always wearing off, the real length is uncertain. But that learned author, on inspecting their sections, would have heen sensible, that many want very little if any por tion of the extremity, although others be greatly blunted, or even broken over by some uncommon degree of vio lence. The largest tusks are said to be brought from Africa, and the straightest from Asia ; and it is though' that those least afford the best ivory. Neverthe less, we do not consider these points as established ; and we are disposed to doubt whether the quality of the ivory is indicated by any external appearances, or whether much dependence can be placed on any, except very simple rules, for judging of it.