[53 | OYSTER CULTURE. 805 
cording to its nature, different kinds of treatment. If it is argilla- 
ceous or muddy it should be cleaned and leveled, leaving the central 
portion higher than the borders, then pounded to give it solidity, and 
finally covered with water until the bottom is thoroughly saturated, when 
the water can be allowed torun out, and the bottom once more pounded 
while itis drying. If the bottom is sandy it is necessary to render it 
impermeable, so that the water may not leak out, and also to consolidate 
it. To accomplish this the ground is worked over and covered with a 
layer of coarse gravel or fragments of shells, upon which is laid a layer 
of clay 30 to 40 centimeters (10 to 12 inches) in thickness, which is then 
treated as already mentioned for the marly bottoms. A bed of concrete 
answers the same purpose, and while it is more costly it is more durable 
A pavement of blocks of sandstone or porphyry, &c., similar to those 
which are used in the pavements of certain of our cities, carefully 
pointed with clay or hydraulic cement, will also make an excellent bot- 
tom. But the clays, especially the reddish clays and the bluish marls, 
should be preferred in all cases where one wishes the oysters to possess 
the greenish tint to which the oysters of Marennes owe their celebrity. 
Surrounding the ground thus prepared are built the dikes which are to 
retain the water in the basins. These should be at least 2 meters in 
height above the bottom, so that a depth of water of from 1.50 to 1.80 
meters can be maintained over the oysters, not all the time, as gen- 
erally a depth of from .35 to .50 of a meter is best, but when it is very cold 
to prevent the injurious effects of frost, and when it is very warm to 
prevent the water becoming too salt from evaporation. These dikes 
should be constructed very solid, so as to resist the great pressure 
which is brought to bear upon them at every spring-tide, and should 
also be covered upon the inside, the same as the bottom, with a layer of 
clay or hydraulic cement, so as to prevent all leakage, which is very dis- 
astrous in these basins, since the water is renewed only at long inter- 
vals. Since these earthen dikes are liable to be injured, making it nec- 
essary to go to the expense of frequent repairs, it would be best, in my 
opinion, to construct them at first in masonry of rough stones and 
cement, and give them solid foundations. The upper portion of the 
larger of these dikes should be sufficiently broad and firm to permit the 
workmen to traverse them easily and without danger, for all the neces- 
sary manipulations of working and inspection. If the height of the 
ground permits, these claires can be formed by excavating in the solid 
earth, in which case it will only be necessary to cover the slopes of the 
banks with a layer of stones set in cement. This system moreover will 
allow of the utilization of lands slightly above the level of the tides, so 
that by uniting the two systems one can arrange three or even more 
rows of claires all upon the same level. 
As to the expense of construction, I judge it will be about the same 
for the two methods, the excavation in the one compensating for the 
masonry in the other. Finally, to avoid or at leastretard the deposit of 
