Basins of the Great Lakes. — Spencer. 95 
benches only remain as fragments about ancient islands ; but if 
we descend to beaches of lower levels we find them well developed 
and containing all the necessary evidence for explaining the rock- 
barriers at the outlets of the lakes. Gen. G. K. Warren, corps of 
engineers, U. S. A. , was the first to suggest the closing of the 
lakes by warpings of the earth's crusfc*. Portions of the high- 
level beaches about the lakes have long been noted. But it was 
Mr. G. K. Gilbert who first connected the beaches upon the south- 
ern and eastern sides of lake Ontario, and measured their great 
rise towards the northeast ; but, as he did not apply his discovery 
to the explanations of the lake-basins, it was first applied by the 
present writerf. The results of Mr. Gilbert's investigations of 
beaches in New York and Ohio, and of the writer's researches in 
Canada, Michigan, New York, and elsewhere, are sufficient to 
form a chapter by themselves, and are still mostly unpublished, but 
I will draw upon them only to the extent of explaining the barriers 
across the outlets of the old valleys. 
The most important raised beach of the Ontario basin is the 
IroquoisX. At the western end of the lake it now rests at 363 feet 
above the sea, but rises slightly to the east and still more towards 
the north, until at four miles east of Watertown it is 730 feel 
above the sea. Still further north-eastward, near Fine, on the bor- 
ders of the Adirondack wilderness, it reaches an elevation of 972 
feet above the sea, beyond which I have made no instrumental 
measurements. At the western end of the lake the uplift is 
scarcely two feet in a mile in the direction of N. 28° E. At and 
beyond the north-eastern end of the lake the uplift is found to 
have increased to live feet in a mile, and in the region of farthest 
observation to somewhat more, in a northeastward direction. 
Thus in the deformed water-level [ have already measured a bar 
rier of about 009 feet raised up at the outlet of the lake. Of 
this, about 530 feet is confined to the region of and beyond the 
eastern ends of the lake, where the later Pleistocene barrier across 
the ancient Laurentian valley lias appeared. Whilst we know 
*Appendix 13, Report of Chief of Engineers, l". s. A., ist.v 
(•See " Notes on the Warping of the Earth's Crust in its Relations to 
theOriginof the Basins of the Great Lakes." Amer. Nat., Feb., 1887, 
pp. 168-71. 
J" Iroquois Beach ; a chapter in the Geological History of Lake Out a 
rid." Proc. Km. Soc. Canada. 1889. 
