1892.] Why the Mocking Birds Left New Jersey. 639 
recollection is that the Professor estimated the present subsid- 
ing as proceeding at the rate of a vertical half inch in a year, 
and the Doctor had gathered other very interesting data, such 
as the change of level of tide-water mills. The rate stated 
is certainly enormous when compared with the time taken to 
produce the subsidence of the cedar swamps or mines. 
The cypress and the cedar, also the arbor-vite, but espec- 
ially the former, loved the sandy levels of the New Jersey 
coast. But with subsidence and the woodman’s axe very little 
of these sheltering copses of evergreens is left. Forty years 
ago an occasional pair of mockers has been known, even in 
the central part of the State by a stream in a deciduous 
tkicket, with catbriers interlaced. But the bird even then was 
rare—and is much rarer now. The hospitable shelters and 
food resources on the shores are gone, and the mocker has vir- 
tually left also. The bird has yielded to the fiat of geological 
change—the inevitable law to which the flora and the fauna 
of the earth must bow. 
Our position is not that these birds can no longer live in 
New Jersey, but that the situation is less inviting than for- 
merly ; in a word, the bird life is harder. As to shelter and 
food, the old summer home has become less hospitable. There 
is a third factor beyond reach in this discussion, that of cli- 
mate. True, we do know something of this as caused by the 
denuding of the land of its native forests; but we know noth- 
ing of that climate when the shores of the State, far-reaching 
into the sea, hugged more closely the thermal Gulf-stream. It 
will appear too, that we have taken no note of the effect of 
contact with civilization, which in the main is less conserva- 
tive than even geologic change. 
In the dialectics the principle is accepted that the exception 
may establish the rule. This, though often true in the mental 
realm, is but rarely so in that of the physical. Hence it is 
not only interesting but quite remarkable to find our position 
fortified by a geological exception, almost on the spot which 
has come directly under our review. Raritan Bay is in part 
bounded by the little peninsula of Sandy Hook. While the 
main is suffering from subsidence of the land and denudation 
