1898-99]. THE IROQUOIS BEACH. 31 
Ontario, giving the beach its name, and bringing out clearly its differ- 
ential elevation toward the northeast, crediting G. K. Gilbert with 
similar work on the south shore of the lake, and furnishing for the first 
time a correct idea of the shores of this old body of water.* Spencer 
looks on the Iroquois water as having been a prolongation of the Gulf of 
St. Lawrence, and so reverts to the theory of marine origin. Gilbert, on 
the other hand, prefers the lake theory, and places an ice dam across the 
wide stretch toward the northeast, where no beach can be found. 
The work of Spencer and Gilbert practically settled the area and 
general character of the shores of the Iroquois water, and settled also 
that the region has been elevated toward the north-east, so that the old 
beach is now 115 feet above Lake Ontario at Hamilton, 170 at Toronto, 
and 385 at Trenton. The rate of increase in elevation per mile toward 
the west end.of the lake is 1.6 feet, while in the neighborhood of 
Watertown, N.Y., according to Spencer, it is five feet.t The rate of 
elevation per mile as shown on the north shore is 1.8 feet between 
Burlington and Toronto, two between Carlton and Scarboro’, and 2.3 
between Scarboro’ and Trenton, showing that the deformation increases 
toward the northeast. Beyond the Ottawa and St. Lawrence valleys it 
has not been found, but there is no land high enough to receive it, even 
if there were no ice dam at the north-east end of the lake to close its 
work at that point. 
In order to represent graphically this increase of deformation toward 
the northeast, the following curve of elevation of the beach has been 
prepared by Dr. Ellis and myself, the heights of the beach above sea 
level, taken mainly from Spencer’s History of the Great. Lakes, being 
used as ordinates, and distances from Hamilton at the west end of the 
lake as abscisse. After numerous trials, it was found that the direction 
north 17° east harmonized the elevations on the two sides of the lake 
most satisfactorily, and this has been adopted in the diagram. In 
reality, as shown by Gilbert,} the isobases or lines of equal uplift are not 
straight, but gentle curves, concave towards the north-northeast. 
The shore of Lake Iroquois lies outside the area of Lake Ontario 
everywhere except for half a mile at Scarboro’ Heights, where a 
promontory extended south beyond the cliffs of the present shore. 
THE IROQUOIS SHORE AT TORONTO. 
During the past two years the increase in building operations in 
Toronto has caused the opening of a number of sand and gravel pits 
* The Iroquois Beach, Trans. Roy. Soc. Can,, Section IV., 1889, p. r21, ete. 
+t History of the Great Lakes, pp. 47 and 48, 
t Recent Earth Movements in the Great Lakes Region, U.S, Geol. Sur., 1898, p. 604, 
