WORKING OF IVORY 249 



being very good, he still found that they were absolutely 

 useless, since even he could not make them respond as was 

 possible with a properly cut ball. 



In connection with the resiliency that makes ivory such 

 an indispensable material for the billiardist, we may note 

 that this quality has been recognized recently by golf 

 players at whose request a circular disk or thick button of 

 ivory is sometimes put in the head of the driver. It has 

 been found experimently that mammoth ivory is poor 

 material for billiard balls, as it has lost to a considerable 

 extent the resiliency so characteristic of ivory. Some 

 good judges have regarded the bleaching which is generally 

 resorted to in order to impart a dead-white hue to the balls 

 as detrimental to their quality, since it dries out the gela- 

 tine to a noticeable extent, and is apt, in this way, to modify 

 unequally the natural density of the ivory.* For billiard 

 balls of superior quality, one of the centres of manufactur- 

 ing is New York City. 



The relative structural uniformity of ivory billiard balls 

 and those made of celluloid has been tested, the latter having 

 been rendered equivalent in specific gravity by the addition 

 of filling materials. The test was made by placing the balls 

 in a cup of mercury to which a small quantity of benzol had 

 been added; when placed in this solution the celluloid ball 

 floated without turning, while the ivory ball gyrated some- 

 what before coming to rest, this showing that its centre of 

 gravity was not exactly in the centre of the sphere as was 

 the case with the celluloid ball. Nevertheless, celluloid 

 balls do not "take the cue" as ivory balls do, and also lack 

 many other of the special qualities of the latter. It is 

 claimed that balls made of the synthetic composition "bake- 

 lite" are even superior to those made of ivory. 



*Alfred Maskell, "Ivory in Commerce and in the Arts," Cantor Lectures (Lecture III), 

 Journal oftlie Society of Arts, Vol. LIV, No. 2817, November 16, 1906, p. 1177. 



