898 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [14] 
be 40 to 50 centimeters (16 to 20 inches), and in the latter from 15 to 20 
(6 to 8inches). Both are dug in the ground to the required depth. The 
sides are formed of boards held in place by strong stakes and supported 
on the outside by a bank of clay. Their bottoms are covered with sand 
and fine gravel. A small sliding door or a mere hole filled up with pot- 
ters’ clay suffices to empty them when necessary. The claires are in gen- 
eral from 30 to 40 meters (100 to 130 feet) long by 4 to 5 meters (13 to 
16 feet) wide, and it is advisable to divide them into several compart- 
ments by wooden or tile partitions, in order to prevent the wind from 
agitating the surface of the water too strongly, to the injury of the walls 
and young oysters. 
Construction of “ambulances.” —A fter the claires the parker prepares his 
ambulances as we have before described them. The ambulance of stone 
and brick belonging to M. Michelet forms quite an extensive building, 
and cost in the neighborhood of 600 francs ($120). The parkers usually 
content themselves with wooden boxes 2 meters (65 feet) in length, 1 
meter (34 feet) in width, and from 12 to 15 centimeters (5 inches) in 
depth. The bottom of these boxes are now covered with wire netting, 
and the tops also sometimes with the same. Constructed in this manner, 
however, they are liable to be invaded by mud which passes through 
the meshes of the netting. Coverings made of boards or of tarred cloth 
seem to be preferable and are much more economical. The oysters in 
the ambulances should always be covered with water. The boxes are 
generally placed in claires and fastened upon stakes which sustain them 
at an elevation of 10 centimeters (4 inches) from the bottom. 
Choice and preparation of collectors.—These preparations being com- 
pleted, collectors must now be arranged. Notwithstanding the pre- 
dominance of tiles, boards, fascines, and strings of shells are still used at 
Arcachon. But, whatever may be the kind of collector employed, there 
is one precaution which is never neglected, and that is to scatter over 
the bottom, as thickly as possible, oyster and other shells, which offer at 
slight expense one of the best means of retaining and fixing spat. In 
order to prepare the tile as a collector, it is coated over with a substance 
destined to facilitate the removal of the oyster. It is plunged several 
times into a bath of hydraulic cement and water, and when it is sufficiently 
dry it receives in the same way a layer of ordinary mortar (one part of 
lime and two parts of fine sand), which should be from 2 to3 millimeters 
(;'5 to 4 of an inch) in thickness. Some parkers substitute a second layer 
of hydraulic cement for the mortar; the advantage claimed being that the 
tiles are made smoother, are less easily soiled, and retain the spat much 
better, while they do not need to be cleansed to fit them for use the fol- 
lowing year. On the other hand the use of mortar renders the separa- 
tion easier. 
Barges.—The organization of a park is generally completed by the 
accession of a barge, containing two rooms for the guard, and the pur- 
chase of a small boat for communication between the park and the shore. 
