246 On the Economical Uses of some species of Testacea. 
in dredging, those which are too small are thrown back again. The 
season begins on the first of September, and lasts till April. The 
dredgers make use of a peculiar kind of net, which is very strong, 
and fastened to three spikes of iron; this they drag along the bottom 
of the sea, and thus force the oysters into it; each boat requires five 
men, and they dredge in water from four to fifteen fathoms deep. 
The green oysters are all procured at or in the neighborhood of 
Colchester. When they wish to give them this color, they throw 
them into pits dug about three feet deep in the salt marshes, which 
are overflooded only at spring tides, and to which they have sluices 
to let out the salt water till it be about one and a half feet deep. 
These pits become green, and communicate their color to the fish in 
four or five days, although they commonly let them continue there 
six weeks or two months, in which time they will become a dark 
. The color has recently been ascertained to arise from con- 
ferve, and other marine vegetable matter, decayed by the heat of 
the sun, on which the animal feeds. A very common and very mis- 
taken opinion exists, especially among foreigners, that not only those, 
but all English oysters are impregnated with copper, ‘ which they get 
from feeding off copper banks ;’ such we believe would be quite as 
injurious to the animal itself as it could be to us, and the fancy can 
only have arisen from the strong flavor peculiar to this fish. Green 
oysters are comparatively little esteemed in the present day. 
Use.—The great value of this animal is for diet. The shell was 
at one time supposed to possess peculiar medicinal properties, but 
analysis has shown that the only advantage animal carbonates have 
over those of the mineral kingdom, arises from their containing 00 
metallic or foreign substance.* The inhabitants of the shores of 
Hindoostan did, two centuries since, and perhaps still may, use it in 
the same manner. The fish is recommended by the doctors where 
great nourishment and easy digestion are required, the valuable qual- 
ity being the quantity of gluten it contains. In the northeastern parts 
of England, old houses may be seen with their tops and gable ends 
ornamented with these shells, only the inside being exposed; @ cus- 
tom which is said, we know not with what truth, to have been intro- 
duced from Holland. In some parts of Scotland the shells are used 
as manure, tnd found very excellent and stimulating 5 ; in other places 
are as lime. 
_.. * Todine is found in some of them.— Ed. 
