MOLLUSCA. 231 
porcellaneous shells. In general, however, it happens that, 
when shells become dry, they lose much of their natural 
lustre. This may be very easily restored, by washing them 
with a little water, in which a small portion of gum arabic 
has been dissolved, or with the white of an egg. This is 
the simplest of those processes which are employed, and is 
used not only by the mere collector, but by the scientific 
conchologist. There are many shells of a very plain ap- 
pearance on the outside, by reason of a dull epidermis or 
skin with which they are covered. This is removed by soak- 
ing the shell in warm water, and then rubbing it off with a 
brush. When the epidermis is thick, it is necessary to mix 
with the water a small portion of nitric acid, which, by dis- 
solving a part of the shell, destroys the cohesion of the epi- 
dermis. This last agent must be employed with great cau- 
tion, as it removes the lustre from all the parts exposed to 
its influence. The new surface must be polished with lea- 
ther, assisted by tripoli. But, in many cases, even these 
methods are ineffectual, and the file and the pumice-stone 
must be resorted to, in order to rub off the coarse external 
layers, that the concealed beauties may be disclosed. Much 
address and experience are necessary in the successful em- 
ployment of this last process. But it must be confessed that 
the reward is often great. When thus prepared, even the 
common mussel is most beautiful. 
The arrangement of shells in a cabinet must depend, ina 
great degree, on the taste and fortune of the collector. If 
ornament is the object in view, it will be indispensably ne- 
cessary to have the shells placed in glass cases, where they 
may be distinctly seen. But where a collection of shells is 
formed for amusement, they may be kept in drawers, each 
species placed in a paper case, or in a cup of wood, glass, or 
