244 Conchology. 



dipped several times in diluted aquafortis, that this may be eaten 

 off; and then the shell is to be polished in the usual way with 

 pretty fine emery, or tripoli, on the hair of a fine brush. When 

 it is only a pellicle that hides the colors, the shell must be steeped 

 in hot water, and after thatthe skin is worked off by degrees with 

 an old file. This is the case with several of the cyHnders, which 

 have not the natural polish of the rest. 



When a shell is covered with a thick and fatty epidermis, as 

 is the case with several of the muscles and tellinae, in this case 

 aquafortis will do no service, as it will not touch the skin: then 

 a rough brush and coarse emery are to be used; and if this does 

 not succeed, seal skin or as the workmen call k^ fish skin^ and 

 pumicestone are to be employed. 



When a shell has a thick crust, which will not give way to any 

 of these means, the only w'ayleft is to plunge it several times into 

 strong aquafortis, till the stubborn crust is wholly eroded. The 

 limpets, Auris marina^ the helmet shells, and several other species 

 of this kind, njust have this sort of management; but as the de- 

 sign is to show the hidden beauties under the crust, and not to 

 destroy the natural beauty and polish of the inside of the shell, 

 the aquafortis must be used in this manner. A long piece of wax 

 must be provided, and one end of it made perfectly to cover the 

 whole mouth of the shell; the other end will then serve as a han- 

 dle, and the mouth being stopped by the wax, the liquor cannot 

 get into the inside to spoil it; then there must be placed on a ta- 

 ble, a vessel full of aquafortis and another full of common water. 



The shell is to be plunged into the aquafqrtis, and after re- 

 maining a few moments in it, is to be taken out and plunged into 

 the common water. The progress the aquafortis makes in ero- 

 ding the surface is thus to be carefully observed every time it is 

 taken out: the point of the shell, and many other tender parts, 

 are to be covered with wax to prevent the aquafortis from eating 

 them away; and if there be any worm holes, they also must be 

 stopped up with wax, otherwise the aquafortis would soon eat 

 through in those places. When the repeated dippings into the 

 aqualbrtis show that the coat is sufficiently eaten away, then the 

 shell is to be wrought carefully with fine emery and a brush; and 

 when it is polished as high as can be by this means, it must be 

 wiped clean, and rubbed over with gum water or the white of an 

 egg. In this sort of work the operator must always have caution 

 to wear gloves; otherwise the least touch of the aquafortis will 

 burn the fingers, and turn them yellow; and often, if it be not 

 regarded, will eat off the skin and the nails. 



