Conchology. 345 



These are the methods which are to be used which require but 

 a moderate quantity of the surface to be taken off; but there are 

 others which require to have a larger quantity removed and to be 

 taken ofF deeper; this is called entirely scahng a shell. This is 

 done by means of a horizontal wheel of lead or tin impregnated 

 with rough emery; and the shell is wrought down in thesame man- 

 ner in which stones are wrought by the lapidary. Nothing is more 

 difficult, however, than performing this work with nicety; very often 

 shells are cut down too far by it, and wholly spoiled ; and to avoid 

 this, a coarse vein must be often left standing in some place, and 

 taken down afterwards with a file, when the cutting it down at the 

 wheel would have spoiled the adjacent parts. 



After the shell is thus cut down to a proper degree, it is to 

 be polished with fine emery, tripoli, or rotten stone, with a wood- 

 en wheel turned by the same machine as the leaden one, or by 

 the common method of working with the hand with the same in- 

 gredients. When a shell is full of tubercles or protuberances 

 which must be preserved, it is then impossible to use the wheel; 

 and if the common way of dipping in aquafortis be attempted, the 

 tubercles being harder than the rest of the shell, will be corroded 

 before the rest is sufficiently scaled, and the shell will be spoiled. 

 In this case, industry and patience are the only means of effecting 

 a polish. A camels-hair pencil must be dipped in aquafortis; 

 and with this the intermediate parts of the shell must be wetted, 

 leaving the protuberances dry; this is to be often re])eated; and 

 after a few moments the shell is always to be plunged into water 

 to stop the erosion of the acid, which would otherwise eat too 

 deep, and destroy the beauty of the shell. When this has suffi- 

 ciently taken off the foulness of the shell, it is to be polished with 

 emery of the finest kind, or with tripoli, by means of a small 

 stick; or the common polishing stick used by the goldsmith may 

 be used. 



This is a very tedious and troublesome thing, especially, when 

 the echinated oysters and murices and some other such shells, 

 are to be wrought; and what is w^orst of all, when all this 

 labor has been employed, the business is not well done; for there 

 still remain several places which could not be reached by any in- 

 strument, so that the shell must, necessarily, be rubbed over with 

 gum water or the white of an egg afterwards, in order to bring 

 out the colors and give a gloss; in some, it is even necessary to 

 give a coat of varnish. 



These are the means used by artists to brighten the colors and 

 add to the beauty of shells; and the changes produced by polish- 

 ing in this manner are so great, that the shell can scarcely be 

 44 



