462 BOTANICAL GAZETTE [DECEMBER 
and dikes. Fresh water peat, formerly beyond the reach of salt 
water, may now be buried under a layer of salt peat. In short, 
most of the phenomena usually cited as proofs of general coastal 
subsidence will be produced by a local rise of the high tide caused by 
change in the form of the shore line. If the bay narrows inland as 
shown in fig. 6, the tidal wave will increase in height as it advances, 
so that the level of high tide at the head of the bay will rise far 
above that of the open sea (ED, fig. 7). In this case all the trees 
between A and E will be killed at the head of the bay, and the 
appearance of subsidence will be unusually pronounced. 
Fig. 8 represents the consequences of the opposite type of change. 
When the bay was open to the sea, the waves cut a cliff (C) and 
bench (B). But the construction of a barrier beach (D) has so 





1c. 8.—Diagram showing fictitious elevation of the coast; before the barrier 
beach (D) was constructed, the tide in the bay rose as high as in the open sea, and 
the cliff (C) and bench (B) were carved by the waves; since the building of the barrier 
beach, high tide (HT) in the bay is lower than in the ocean, the cliff and bench are 
no longer reached by the waves, and appear to represent an “elevated shore line”; 
the uniform altitude of the beach ridges on the barrier beach shows that the relative 
level of land and sea have long remained constant. 
reduced the level of high tide in the bay that the waves no longer 
reach the cliff or the inner part of the bench. These become covered 
with trees and other fresh vegetation, and constitute what is usually 
called an “elevated shore line.’ Cliffs and benches of this origin 
have been cited as proofs of recent coastal elevation. 
In applying the above principle to the interpretation of supposed 
elevations and subsidence of the land, the following points should 
be kept in mind: 
a) If, instead of a sudden rupture of the barrier beach, we have 
a gradual enlargement of the inlet, the shores of the bay will appear 
to undergo slow and progressive subsidence. The gradual closing 
of an inlet, or the progressive shifting of its position, will likewise 
