Industrial and Manufacturing Uses of Shells. 275 

 The black helmet, on account of the advantaeeous 



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contrast of colour in the layers, produces very effective 

 cameos, the carved figure of the white upper layer being 

 strongly relieved by the dark, almost black, ground supplied 

 by the second layer. The shell is first cut into pieces, the 

 size of the required cameos, by means of diamond dust and 

 the slitting mill, or by a blade of steel fed with emery 

 and water. 



It is then carefully shaped into a square, oval, or other 

 form on the grindstone, and the edge finished with oil- 

 stone. It is next cemented to a block of w r ood, which 

 serves as a handle to be grasped by the artist while tracing 

 out with a pencil the figure to be cut on the shell. 



The pencil mark is followed by a sharp point, which 

 scratches the desired outline, and this again by delicate 

 tools of steel wire, flattened at the end and hardened, and 

 by files and gravers, for the removal of the superfluous 

 portions of the white enamel. A common darning-needle, 

 fixed in a wooden handle, forms a useful tool in this very 

 minute and delicate species of carving. The careful mani- 

 pulation necessary in this work can only be acquired by 

 experience ; the general shape must first be wrought, care 

 being taken to leave every projection rather in excess, to be 

 gradually reduced as the details and finish of the work are 

 approached. To render the high parts more distinct 

 during the process of carving they are slightly marked in 

 black. 



Throughout the cutting, great caution must be observed 

 that in removing the white thickness the dark ground is 

 not damaged, for the natural surface of the dark layer is 

 far superior to any that can be given artificially ; indeed, 

 should the ground be broken up at one part, it would be 

 requisite to remove the entire scale or lamina from the 



