,398 



IVORY. 



Iroty. warns of Linnwus, afford the hardest and whitest of 

 w >- ' all ivory. Some are reported to be two or three feet 

 10 in length, and to weigh thirty pounds, though usu- 

 ally they do not exceed hvo or three. They are short, 

 null very much curved. A large hollow occupies the 

 wide end, as in the tusk of the $ea cow and the ele- 

 phant ; the centre or nerve is of a dark triangular shade. 

 A rough glassy enamel covers the cortical part, of ex- 

 cessive hardness, and which strikes fire with steel : It 

 can scarcely be removed with a file, and blunts a tool 

 of the highest temper. The texture of this ivory near- 

 ly resembles that of the former in concentric layers ; 

 but they are as fine as human hairs, and, in a transverse 

 section, are hardly perceptible by the naked eye. When 

 brought into view by magnifiers, and a favourable 

 light, they are exceedingly numerous, but of, irregular 

 diameter. Little is exposed "by a longitudinal section, 

 unless when very thin ; and then Appear what may be 

 supposed the successive layers, proceeding diagonally 

 from the core. 



Ivory of the We shall conclude our observations on the nature of 

 narwhal. ivory with an account of the tooth or horn of the nar- 

 whal, one of the cetaceous tribe. The largest are ten feet 

 long, and some inches thick at the lower extremity, 

 forming a slender cone of a spiral figure. This tooth 

 consists of ivory of the finest description, equally hard 

 as elephant's ivory, and susceptible of a higher polish. 

 But we do not know that all of it is of the same cha- 

 racter ; and a prejudice against its ordinary use sub- 

 sists among workers in ivory. Its texture is singular, 

 differing in most respects from all other ivory. On 

 giving the highest polish to a transverse section of 

 about an inch and a half in diameter, the cortical 

 part proved of a very dull white, somewhat of a green- 

 ish cast, of a hard horny consistency, and about an 

 eighth of an inch broad. Interposed between it and 

 the substance of the tooth there appeared a bright 

 white circumferential line, narrower and much hard- 

 er than the bark. The surface was beautiful, quite 

 homogeneous to the naked eye, with a few of the faint- 

 est concentric circles more transparent than the rest. 

 Nothing more is perceptible without reducing the 

 thickness of the ivory, and resorting to the micro- 

 scope. This being done, the faint circles of a section, 

 about a COth part of an inch in thickness, prove to 

 consist of three lines, that in the middle darker than 

 the others. Innumerable radiations of a fine feathery 

 appearance proceed from around the central cavity, and 

 terminate somewhat* within the circumferential line, 

 but again becoming more conspicuous in what we have 

 denominated the cortical part. These are not unlike 

 the spiculae shooting out during the crystallization of 

 certain salts. But all are tubular, and the fact is de- 

 monstrated on subjecting a very thin longitudinal sec- 

 tion to a magnifier of considerable power. We have 

 not witnessed this peculiar conformation in any other 

 ivory, though it is not improbable that the striae or radia- 

 tions above alluded to in that of the elephant and whale's 

 tooth, may be analogous to it. No porosity was dis- 

 covered in a longitudinal portion of the former, reduced 

 so thin as to be bent double with ease. On throwing 

 a particular light on the surface of the narwhal's ivory, 

 an irregularity is visible from the tubular formation, 

 consisting of innumerable minute horizontal cavities. 

 1'his peculiar structure merits farther examination, in 

 which suitable attention should be paid to portions from 

 various teeth. It is obvious, from what has been said, 

 that the bony process of the narwhal is more probably a 

 tooth than a horn. 



Considerable anomalies are seen in the structure of i vor y, 

 the different kinds of ivory, ajjd every tooth, seems to 

 have something peculiar to itself, especially in .the ar- 

 rangement of the concentric circles. In so far as our ob- 

 servations go, the most transparent is the hardest, which 

 is particularly exemplified in the pellucid rings above 

 alluded to. Thus, on reducing a plane surface of 

 ivory by any ordinary mechanical operation, they 

 will remain prominent, though the rest yields under 

 it. The line interposed between the bark and the 

 substance is also the hardest of the whole. We have 

 seen the tusks of phocae free of enamel, and having a 

 thick bark, with fine ivory, which we were unable to 

 trace to any of the ordinary species. Circumstances 

 may render it difficult to ascertain the fact, especially 

 if the ivory be not recent. On examining a small por- 

 tion of an elephant's tusk lately discovered in Ayrshire, 

 it proved somewhat harder than recent ivory. The ex- 

 terior consisted of an extremely thin coat of a deep 

 brown colour, surrounding a portion of a broad circu- 

 lar ring, wherein very numerous concentric lines were 

 visible. Within this appeared what seemed common 

 ivory. But the fragment was small, which rendered its 

 peculiarities less obvious ; and these consisted chiefly 

 in the concentric lines. 



Ivory is found, by analysis, to consist of the phosphate 

 of lime, and a gelatinous substance. The yellow colour 

 acquired by exposure to the air, is supposed to arise 

 from the combination of the gelatinous matter with the 

 oxygen of the atmosphere. It is said that oxygenated 

 muriatic acid will restore the original whiteness. Some 

 ivory is exceedingly white from the beginning, and 

 some w"hitens in drying. It is discoloured by being 

 frequently handled, though the keys of an organ or pi. 

 ano most commonly used are said to retain their white- 

 ness longer than the others. The colour may be re- 

 newed by removing the external surface, provided the 

 discoloration be only superficial. Artists distinguish 

 ivory into white and green, the former being character- 

 ized by a whitish or lemon- coloured bark. When cut 

 up, it is of a faint olive or greenish hue, but soon be- 

 comes of a beautiful white. 



Ivory is applied to a vast variety of purposes in the Purposes t* 

 arts. Its hardness and texttfre adapt it for many which ivory 

 works where wood would be speedily destroyed, and 

 to which metal is unsuitable. The most elegant sculp, 

 tures are executed in ivory, not only of images, but 

 even of landscapes after nature ; whereof the finest 

 parts can only be compared to lace. It is universally 

 employed for every kind of turnery, of which admi- 

 rable specimens are brought from foreign countries ; 

 such as several hollow spheres, included within each 

 other, successively, even to the number of 14>, 15, or 

 more ; while the outside is carved in a variety of 

 figures in open work. From its elasticity, it is used 

 exclusively for making the balls employed in games of 

 skill ; as billiards ; and also in those for demonstrating 

 the doctrines of collision It is sometimes formed in. 

 to baskets of considerable size, elaborately wrought ; 

 and we have heard of furniture composed exclusively 

 of ivory, inlaid with gold. The scales of almost all 

 mathematical instruments are made of it ; for which, 

 if properly and sufficiently seasoned, it is in many re- 

 spects superior to brass, and fine ivory is almost always 

 used for miniature paintings. One of the purposes to 

 which it is most extensively and usefully applied, is 

 comb-making ; in which seventy teeth may be cut to 

 the length of an inch, all executed by a saw ; and 

 the ivory of the sea horse has superseded every other 



