272 The Commeixial Products of the Sea. 



By Brooks and Faith — 



84 baskets, 13 bags, and 10,000 loose green snail. 

 230 packages and 10 tons of loose Japan ear shells. 

 12,000 turbos. 



By Donald Gray and Sons — 



39 cases Manila and 51 cases Bombay M.O. P. 

 I case red shank shells. 



By John Griffin and Son — 



194 cases Bombay M.O.P, 

 381 bags Maldive cowries. 

 5 tons Japan green ear. 



Most of the univalve shells are of the character called 

 porcelanous, from their brittleness, translucence, and the 

 resemblance of their fracture to that of porcelain. But this 

 fracture, Avhen examined by a microscope, reveals a struc- 

 ture of thick parallel layers, usually of a fine fibrous nature, 

 at right angles to the external surface. The soluble part 

 of these shells is carbonate of lime, the particles of which 

 are cemented together with a very minute proportion of 

 animal mucus. The hard and compact nature of such 

 shells, and their generally smooth surface, prevent their 

 being cut by the ordinary tools which are available for the 

 less hard and frangible nacreous shells ; it is, therefore, 

 necessary to treat them with emery, rotten-stone, and other 

 substances harder than themselves. 



Such shells generally require rather to be polished than 

 cut, but where it is necessary to divide them, in order to 

 exhibit their sections, they are operated upon by means of 

 the slicer with diamond powder. 



Certain description of these shells are well adapted for 

 cameo-cutting, from their substance being made up of dif- 

 ferently coloured layers, and also from a difference of hard- 

 ness and texture in the various layers, some approaching 



