139 
extension of the beds due to natural unassisted causes, their 
great increase in area during the last thirty years must be as- 
signed to other agents. 
The diminution of the number of oysters may be affected 
by several natural causes. An increased deposit of earthy 
or vegetable matter upon the beds would, if in sufficient 
quantities to bury the oyster, effect fhe destruction of both old 
and young. No such deposit has been noticed, nor could it well 
occur without showing its presence in other ways, principally 
by changing the channels and causing shoals ; but no such 
changes have occurred, my investigation showing but slight de- 
viations in either channels, shoals or character of the bottom 
from that established by the first hydrographic survey of the 
locality. A change in the character of the water and bottom, 
which would probably follow a change of channel, and might 
occur without such change, might, by depriving the animals of 
their proper food , cause their deterioration and destruction. But 
such a change, though it would certainly diminish the numbers 
on the beds, would do so suddenly and the evil effects would be 
noticed in the oysters remaining, their quality and flavor, in- 
deed, their vitality, being very much impaired. No such impair- 
ment has been observed, however, the oysters being larger and 
finer than when the beds were first discovered. That fact alone 
will eliminate many quantities from the equation, for any 
natural cause injurious to all the oysters on the beds would be 
evident at once by an examination of those found at present. 
If, however, the destruction or non-production of the neces- 
sary number of young is accomplished by means that are not 
harmful to the mature oyster, a cause is discovered for the 
diminution of all in harmony with the existing facts. Con- 
sidering first the destruction of young; large numbers, immense 
when compared with the ordinary production of other ani- 
mals, are without doubt naturally destroyed by the falling of 
the “spat” upon unfavorable grounds, the prevalence of heavy 
freshets which would drive the “ brood ” into the Bay, and 
probably cause its loss, and the ravages of various enemies. 
But all these causes have been in operation continually since 
the first formation of the beds, and the animals have survived 
