878 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [54] 
ROOF COLLECTOR. 
The roof collector (Fig. 2) may be used advantageously instead of the 
stones, which serve at some points, for the purpose of keeping the spat 
in the parcs, or it may supplant the wooden collectors where these are 
subject to the invasion of teredos and of other wood-eating mollusca. 
The roof collector is supported on trestles made of cross-pieces nailed to 
stakes, which rise above the bottom from 15 to 20 centimeters. 
The number of trestles is increased or diminished according to the 
area which is to be covered. 
The tiles, which are the chief elements of the roof, being susceptible 
of different combinations, allow the form to be varied at will. 
These tiles may be arranged in parallel and contiguous rows, and 
thus form a simple complete roof. 
In all the parcs where the action of the water is very strong the 
different rows of tiles should be secured to one another by means of a 
galvanized iron wire, or with stones placed here and there over their 
surface. 
A double roof may be formed (Fig. 3), consisting of an open work of 
tiles covered by a series placed close together. 
The tiles may be placed between wooden supports (Fig. 4) in rows, 
covering, without touching each other, and forming, with the bottom 
upon which they rest, an angle of from 30 to 35 degrees. 
They may also be arranged in the shape of a tent, with both ends 
open and more or less extended, as in Fig. 5. 
In this last combination, the tiles touching the bottom will act as a 
mutual support to one another, and can be strengthened by placing 
stones along the line of contact with the bottom; thus the use of wood 
becomes unnecessary; the apparatus is consequently protected from 
destructive animals. The embryos can be gathered from this kind of 
collector more easily and with less loss than from those made of stones. 
HIVE-COLLECTOR WITH MOVABLE TRAYS. 
The hive-collector with movable trays, although of limited dimen- 
sions, offers, nevertheless, to the spat multiplied points upon which to 
fasten themselves, and the independent collectors, which form the essen- 
tial elements, offer the most favorable conditions for the complete 
development of the young oysters. 
This apparatus (Fig. 6) is composed of an enveloping part, consisting 
of a chest made of light wood, rectangular in shape; measuring 2 me- 
ters in length, 1 meter in width, and 1 meter in height; without a bot- 
tom; with a cover made of several pieces (D), held in position by a 
cross-piece (T) passed through cleats at the handle (A). The chest is 
bored at the extremities with a double series of holes, either square or 
round, corresponding to each other, and large enough to admit beams of 
6 to 7 centimeters in diameter (S); it is held together on the sides by 
