PENHALLOW] DEVELOPMENT OF CERTAIN MARSH LANDS 2 
conform to the extension of existing rivers. Such channels are often 
cut to a depth of one hundred or two hundred feet or even more, and 
they thus form veritable cañons which are regarded as evidence of river 
action, and they thus furnish proof of a former great continental 
elevation. On this hypothesis, their present position is to be interpreted 
as representing a corresponding continental depression which has 
developed, in some cases at least, since Pliocene time. This submer- 
gence, however, has not proceeded continuously or at a uniform rate, 
but intermittently, so that periods of elevation have alternated with 
periods of depression in a more or less irregular sequence; but the final 
resultant of these oscillations is expressed in a progressive subsidence 
which is now proceeding at the rate of two feet per century. 
From this it is obvious that Spencer adopts without hesitation, the 
conclusions reached by Cook and by Jaggar, as well as by other 
observers, and from the collective evidence now at hand, it would seem 
reasonable to conclude that the entire coast line of North America, from 
the Gulf of Mexico to Greenland, is slowly subsiding. I have thought 
it desirable to make this point clear because it will not only be found 
to constitute an important factor in reaching a solution of certain well 
defined features in the growth of the marsh land, the description of 
which constitutes the special subject of this paper, but to receive 
support of the most definite kind from the actual growth of the marsh 
itself. 
The Marsh at York, Maine. 
At York, Maine, (Fig. 1) just over the boundary line from the 
town of Kittery, there is a salt marsh which is approximately one and 
three-fourths mile long by one mile in greatest width. Its position is 
such as to lie between Cutts’ Island and the main land, coinciding very 
nearly with the entire length of the former and extending for fully three- 
fourths of a mile beyond its northern boundary. That portion of the 
marsh which extends along the inner shore of Cutts’ Island, is a narrow 
area which gradually diminishes in width toward the south, and finally 
terminates at the bridge connecting the island with the mainland 2t 
Chauncey Creek. From the main body of the marsh another arm of 
diminishing width, projects toward the west and terminates above the 
bridge of the York Harbor and Beach Railroad. This is the real head 
of the marsh, and it marks the location where a fresh water stream 
enters from the higher land to the west, on its way to the ocean. 
The shore line of the marsh, with respect to both Cutts’ Island 
and the mainland, is composed of a series of rather bold, often con- 
tinuous ledges which rise more or less abruptly to several feet above 
