THE OYSTER. 121 



worn away, leaving the oyster quite firmly fixed to 

 the tile. 



Others, on the contrary, who prefer to separate the 

 oysters entirely from the tile with the blade of a 

 knife, when they are about six months old, generally 

 cover the tile with two layers, and proceed in a different 

 manner. 



Quicklime is slacked just before it is to be used, and 

 is put, while still in a state of ebullition, into a large 

 vat, where two- thirds the same quantity of sand have 

 been placed. The mixture is stirred until it has at- 

 tained the consistency of clear broth. The collectors, 

 held by the lower end, are dipped into the vat. One 

 immersion suffices, after which they are taken in hand- 

 barrows and exposed to the air to dry before setting 

 them up. This excellent coating should be prepared 

 with fresh water only ; sea-water prevents its adhering 

 for any length of time to the tiles, and if it comes off 

 the labor is of course lost. After this coating of lime 

 has hardened, the tiles are dipped a second time into 

 a bath of hydraulic cement, after which they are ready 

 for use. 



Tiles may be used as spat-collectors in either deep 

 or shallow water. On the French coast they are chiefly 

 employed above low-tide mark or in very shallow 

 water, and they are then spread out so as to cover a 

 considerable area. In some cases lines of stakes are 

 driven into the ground, about a foot apart, transverse 

 string-pieces are fastened to them about a foot above 

 the bottom, a row of tiles is laid upon them, concave 

 10 



