18 ROYAL SOCIETY OF CANADA 
through which wanders the streams which carried the land waters to the 
open ocean. When the lagoons behind the sand beaches have become 
shallowed to a depth of ten to twenty feet (sic), certain low-grade 
flowering plants mostly of grass like form, begin to convert the areas into 
marine marshes—wide savannas which are covered by the sea for but 
an hour or two a day, during the time of high tide.’ As a secondary 
feature of their growth, the gradual accumulation of marine animals, 
especially mollusca, adds an important feature to the gradual filling up 
of the lagoon. Eel grass soon becomes established in the more shallow 
areas and further aids in the retention of silt brought in by every tide, 
while all about the shore there are soon established plants which readily 
thrive under intermittent immersion in salt water. All of these factors 
combined, gradually extend the shallow shore line farther and farther 
toward the center of the water field until eventually, only a narrow 
channel for the outward flow of fresh water is left and majntained by 
erosion; and in this way a marsh is formed, the general surface of which 
is but slightly above high water mark. 
While this description may be held to be true with respect to some 
of the marshes on the Atlantic coast, it is not true of others, and due con- 
sideration is not given to the fact made evident by our studies that an 
entirely different course of development may apply, involving the abrupt 
conversion of a fresh water bog into a salt marsh by the sudden intru- 
sion of sea water. Yet again, the famous marsh lands of the Annapolis 
valley in Nova Scotia, long since reclaimed from the sea, as well asi the 
marshes at Chignecto, New Brunswick (4), afford illustrations of still 
another type of development. In both cases the marshes resulted from 
the silting up of shallow, interior basins in process of subsidence, by 
material brought in by the tides and derived from the softer rocks of 
neighbouring localities. 
A factor of great importance in the formation of at least some of 
the salt marshes, and evidently so in the case under discussion, is the 
gradual subsidence of the general area within which they lie. This 
feature has not been discussed by any previous investigators so far as 
I am aware, but our own investigations go to show that it is the only 
means of explaining some of the observed phenomena, particularly the 
abrupt conversion of a bog into a salt marsh. 
One of the earliest records relative to the sinking of the Atlantic 
coast line appears to have been made by Mather (5, 19) who wrote in 
1843 that “The coast of Long Island on the south side, from Montauk 
point to Nepeague beach, a distance of about ten miles, is constantly 
washing away by the action of the heavy surf against the base of the 
cliffs, protected by narrow shingle beaches of a few yards or rods in 
