GEOLOGY : H. L. FAIRCHILD 
231 
It has also been found that in the Ontario Basin the vertical interval be- 
tween the tilted plane of Lake Iroquois and the plane of the sea-level waters 
(Gilbert Gulf) is 290 feet. Extension of the isobases of total uplift westward 
over the Ontario Basin gives very close accordance with the facts of observa- 
tion in that field. 
With the large area of New York State, Ontario basin and western New 
England as a well-determined base it has been possible to extend the study 
eastward over New England and eastern Canada. The result is shown in the 
accompanying map with at least close approximation to accuracy. On the 
small scale the map is somewhat generalized. The broken lines are entirely 
hypothetic only in the Mississippi Valley, where the land uplift may be more 
complicated in time and form. Except in the district west of Indiana and Michi- 
gan the map shows the rise of the continent subsequent to the removal of the 
latest ice sheet. 
For Laborador and Newfoundland reliance is placed on the published data 
of R. A. Daly, with some help from unpublished figures of A. P. Coleman and 
J. B. Tyrrell. 
Precaution is taken in this study to discriminate between features produced 
by sea-level waters and by glacial waters. In the inland areas, in order to 
avoid doubt or cavil as to glacial waters, the main dependance has been placed 
on the summit deltas of streams with southward flow, or with flow directed 
away from the receding ice margin. In the extended paper, noted below, will 
be found a description of field methods, and discussion of criteria for discrimi- 
nating marine features. 
The map shows apparently direct relation between the ice sheet and the 
diastrophic land movement. The area of uplift is the area of glaciation, and 
the amount of uplift is proportionate to the supposed thickness of the spread- 
ing ice cap. The map also shows the effect of land and sea on the flow and 
reach of the ice sheet. The ice deployed on the land but was inhibited by the 
sea; thus producing more rapid flow and steeper gradients along the radii 
toward the nearer sea shores. An independent ice cap is indicated for 
Newfoundland. 
For the fuller discussion, in both methods and results; for description of the 
uplifted sea-level features in western New England, Maine, St. Lawrence and 
Ottawa valleys, Gaspe peninsula, New Brunswick, Nova Scotia, Labrador and 
Newfoundland; and for discussion of possible effects of any change in ocean 
level, the reader is referred to the formal paper in the Bulletin of the Geological 
Society of America, volume 29. 
Former papers by the writer bearing on the subject of recent land uplift are as follows: 
Pleistocene marine submergence of the Connecticut and Hudson Valleys, Bull. Geol. Soc. 
Am r., New York, 25, 1914, (219-242). 
Pleistocene uplift of New York and adjacent territory, Ibid., 27, 1916, (235-262). 
Post-Glacial marine waters in Vermont, Burlington, Rep. Vermont State Geologist for 
1915-16, 1917, (1-41). 
