No. 386. ] FORESTRY AND GEOLOGY. 115 
and snow was identical in all respects with that of to-day over 
the same region. In other words, the flora of the Tertiary 
period had become modified to the new conditions before its 
final extermination by the ice sheet, which extended southward 
in New Jersey as far as Perth Amboy in the east and Belvidere 
in the west. Every species thus far discovered in the Quater- 
nary clays and gravels, or in old peat bogs beneath the bowlder 
till, is identical with some living species, and this evidence of 
modification to meet changing conditions implies a long period 
of time. Such species as were located within the area of 
glaciation were of course absolutely exterminated, while others 
were driven southward, and only such as could exist under 
these vicissitudes remained to reéstablish themselves after the 
final recession of the ice. 
I do not know of any remains of the vegetation of this period 
having been found in New Jersey, and such as have been found 
elsewhere are scanty in amount. 
The final recession of the ice was accompanied by a albeit 
ence of the land, and this subsidence was probably the cause 
of the recession in the same way that the previous elevation 
had been the cause of its accumulation. Several oscillations of 
level occurred, and finally the land assumed the contour and 
topography of to-day. 
At the present time, so far as New Jersey is concerned, a 
slow subsidence of the land is recognized as taking place, which 
amounts to about two feet per century. This rate of move- 
ment, while very slow, is probably no greater than that which 
produced such tremendous changes of level and such far-reach- 
ing effects in the past, and we have but to consider the 
cumulative effects in order to appreciate that a few centuries 
hence great changes in topography may be effected. Even 
within historic times the subsidence of the land has caused the 
Coast line to advance inland in many localities, so that what was 
once upland has become salt meadow, while salt meadow turf 
and tree stumps are found far out in the ocean bottom, beyond 
the present shore line. 
Recognizing these facts, the question analy arises as to 
the ultimate result, provided the present conditions continue. 
