248 The American Geologist. April, 1892 
above the present sea level were found only north and northwest 
of a line drawn from some point probably a little north of New 
York city to another between cape Cod and Boston and through 
Nova Seotia. In the northwestern part of Nova Scotia the limit 
of the uplifted marine deposits was found at a height of only 
about forty feet. Starting from this line the marine limit grad- 
ually rises toward the northwest, so that another line, called an 
isobase, drawn through points which have been upheaved 300 
feet, passes probably from near Niagara falls by Albany, N. Y., 
and Augusta, Maine, to Moncton, N. B., whence it turns back- 
ward, running northwesterly and northerly, crossing the St. Law- 
rence estuary about half way hetween cape Gaspé and the 
Saguenay, 
The 600-ft. isobase is probably to be drawn from Georgian bay . 
past the outlet of lake Ontario, through the southern part of the 
Adirondacks, and thence east-northeast nearly to Moosehead lake. 
Here it makes an abrupt bend to the north and west, similar with 
the loop of the 300-feet isobase at Moncton, and runs first west- 
ward to some point not far from Three Rivers, and thence, turn- 
ing again northeastward, it passes along the north shore of the 
St. Lawrence estuary. The highest directly determined point 
of the former shore line of the submerged area was near Ot- 
tawa, somewhat more than 700 feet above the sea level. 
On the northern slope of the Adirondacks a gravel and sand 
deposit was found, which was evidently formed by a glacial river 
that probably owed its origin to the outlet of lake Iroquois, when 
that glacial lake had sunk from its highest stage and was drained 
between the Adirondacks and the shrinking land-ice. The level 
of the marine limit in the neighborhood shows that the post-glacial 
elevation there has been no more than three-fourths of the hight 
of the Lroquois beach. 
When the ice-barrier of lake Lroquois was removed, it seems 
that the sea must have extended from the prolonged gulf of St. 
Lawrence by one branch into the Ontario basin; by another 
through the Ottawa valley and Lake Nipissing into lake Huron, 
unless that pass was still occupied by the land-ice; and by a third 
branch through lake Champlain down to New York, thus probably 
forming a strait in the Hudson valley. 
The scarcity or absence of marine fossils in these branches or 
inlets of the sea is closely analogous with the conditions of the 
