530 DR. J. W. SPENCER ON THE ORIGIN OF THE 



about the lakes have long been noted. But it was Mr. G. K. Gilbert 

 who first connected the beaches upon the southern and eastern sides 

 of Lake Ontario, and measured their great rise towards the north- 

 east; but, as he did not apply his discovery to the explanations of 

 the lake-basins, it was first applied by the present writer*. 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 still mostly unpublished, but I will draw upon them only to the 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 

 Iroquois t- 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 feet above 

 the sea. Still further north-eastward, near Fine, on the borders 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 five 

 feet in a mile, and in the region of farthest observation to somewhat 

 more, in a north-eastward direction. Thus in the deformed water- 

 level I have already measured a barrier of about 609 feet raised up 

 at the outlet of the lake. Of this, about 530 feet is confined to the 

 region of and beyond the eastern end of the lake, where the later 

 Pleistocene barrier across the ancient Laurentian Yalley has ap- 

 peared. Whilst we know what are the maximum soundings in the 

 river, yet the old channels are so filled with Drift that their depths 

 are not revealed. Still, we know that in one portion of the channel 

 cut out of limestone and more or less filled with Drift, the sounding 

 is 120 feet. A short distance beyond, the channel across the Lau- 

 rentian gneisses shows soundings of 240 feet. The maximum depth 

 of the lake-basin is 738 feet. The deformation recorded in the 

 beaches is more recent than the episode of the Upper Till. Conse- 

 quently, if the continent were at a high level, with the warping, 

 known to have occurred since the Drift was deposited, removed, as 

 shown by the above figures, there would be not only no barrier, but 

 a sufficient slope in the Laurentian Valley for the drainage of what 

 is now the Ontario Basin. 



Furthermore, the presence of the rocky barriers of the Eapids of 

 the St. Lawrence, further east, are wholly accounted for by the 

 terrestrial warpings of the region. Hence I have demonstrated, after 

 a decade of study, that no barrier existed across the Ontario Yalley 

 when it w^as being carved out by the ancient St. Lawrence, and that 

 this barrier is of quite modern origin. 



South-cast of Georgian Bay the average measured warping is four 



* See " Notes on the Warping of the Earth's Crust in its Eelations to the 

 Origin of the Basins of the Great Lakes," Anier. Nat., Feb. 1887, pp. 168-71.^^ 



t " Iroquois Beach ; a Chapter in the Geological History of Lake Ontario," 

 Proc. Koy. Soc. Canada, 1889. 



