[43 ] OYSTER CULTURE. Coo 
employed in certain countries upon the roofs of houses, to gather the 
young oysters. For this collector lines of stakes are driven into the 
ground, over a space of 15 to 20 centimeters of the surface of the bed 
whence it is desired to take the spawn. Upon these stakes transverse 
stringers are fastened, along which tiles are placed side by side, with the 
concave side down (Fig. 12). Here and there heavy stones are placed 
upon the tiles so that neither the current nor the waves can raise or dis- 
place them. But this 
disposition of the tiles 
is not the only one; 
many others can be 
adopted which multi- 
ply the surfaces of 
attachment for the 
young. Thusthetiles 
can be disposed in two 
superimposed and 
crossed layers (Fig. 
13), forming a double 
tile collector, or again, 
as in Fig. 14, they can = : 
be set up obliquely : a 
between the trestles, Fic. 14.—Tile collector. 
which in this case may be placed nearer together ; the tiles forman angle 
of about 25° to 30° with the surface. Still another method, in which the 
wooden trestles are dispensed with, is to arrange the tiles in the form of 
a tent, or pointed roof, kept in place by stones placed between the rows 
Fic. 15—Tile collector, tent form. 
(Fig. 15). This last disposition is the most simple, the least expensive, and 
moreover not a bad one, for it offers a very large amount of surface for 
the attachment of the young. Whichever style of tile collector may be 
employed the concave surfaces of the tiles become covered at the spawn- 
ing season with the young growth, which develops there under excellent 
