MECHANICS AND USEFUL ARTS. 95 



IVORY AS AX ARTICLE OF MANUFACTURE. 



Ax English gentleman stated some interesting facts concerning 

 ivory in a recent lecture at Sheffield. There are several sorts of ivory, 

 differing from each other in composition, durability, external ap- 

 pearance, and value. The principal sources from which ivory is 

 derived are the western coast of Africa and Hindostan. Camaroo 

 ivory is considered the best, on account of its color and transparency. 

 In some of the best tusks the transparency can be discovered even on 

 the outside. The manufacturers have a process by which they make 

 poor ivory transparent, but it lasts only for a short time. A third 

 kind of ivory called the Egyptian, has lately been introduced, which is 

 considerably lower in price than the Indian, but in working there is 

 much waste. By an analysis, the African ivory shows a proportion of 

 animal to earthy matter of 101 to 100; the Indian, 76 to 100; and 

 the Egyptian, 70 to 100. The value of ivory consumed in Sheffield, 

 where it is much used in making handles for cutlery, is about $140,000, 

 and nearly 500 persons are employed in working it up. To make up 

 the weight of 180 tons consumed in that place, there must be about 

 45,000 tusks, whose average weight is 9 pounds each, though some 

 weigh from 60 to 100 pounds. According to this the number of ele- 

 phants killed every year is 22,500 ; but allowing that some tusks are 

 cast and some animals die, it may be fairly estimated that 18,000 are 

 killed every year merely for the ivory, which is contrary to the usual 

 belief that the ivory used comes from the tusks cast by living ele- 

 phants. These estimates, it will be seen, are for Sheffield merely. 



TO RESTORE DECAYED IVORY. 



MR. LAYARD, in his explorations among the ruins of Nineveh, dis- 

 covered some splendid works of art" carved in ivory, which he forward- 

 ed to England. When they arrived there, it was* discovered that the 

 ivory was crumbling to pieces very rapidly. Professor Owen was 

 consulted to know if there was any means of preventing the entire 

 loss of these specimens of ancient art, and he came to the conclusion 

 that the decay was owing to the loss of the albumen in the ivory, 

 and therefore recommended that the articles be boiled in a solution of 

 albumen. The experiment was tried with complete success, and the 

 ivory has been rendered as firm and solid as when it was first en- 

 tombed. 



HOLLOW BRICKS. 



COMPRESSED bricks, with a longitudinal perforation, have been 

 brought into use in England, in the construction of edifices. The 

 plan, however, is not of recent origin, having been known to the an- 

 cients, and applied in the construction of some of the early Christian 

 churches in Italy. These bricks, being considerably lighter than the 

 solid ones, may be used with advantage and economy in the construc- 

 tion of arches, and the partition-walls of dwelling-houses and other 



