Spencer — Deformation of Iroquois Beach, etc. 443 



Art. LYL—The 

 ■of 



The Deformatin of Iroquois Beach and Birth 

 lake Ontario;* by J. W. Spencer. 



Upon receding from the lake and ascending the high country 

 which bounds the Ontario basin, an observer is attracted to the 

 wonderfully plain shore-lines which record the former expan- 

 sion of the waters. The terraces, beaches, scarps, and spits 

 across the mouths of valleys clearly represent the deserted 

 shores. But they are no longer horizontal lines as when laid 

 down at the level of the former waters. As distinctive fea- 

 tures, the beaches were so striking as to attract the attention 

 of the aborigines, who used them as trails across an otherwise, 

 sometimes, muddy country. The early white settlers, in turn, 

 used them as highways and hence we find the " ridge roads " 

 about Ontario as well as about the upper lakes. But the recog- 

 nition of the shore-like characters of the raised beaches, by the 

 early writers, f did not contribute much to the solution of the 

 lake history. 



Nearly fifty years ago, Professor James Hall observed that 

 the beaches in JSTew York were not horizontal. But Mr. G. K. 

 Gilbert was the first who surveyed and measured the deforma- 

 tion of the beaches upon the southern and eastern margins of 

 Lake Ontario, and the writer upon the Canadian side of the 

 lake to beyond Trenton, whence the same beach swings around 

 towards the north and passes into a broken country. The 

 writer has further carried the survey of the same beach about 

 sixty miles beyond Watertown, the limit of Mr. Gilbert's 

 observations. 



There are wide-spread remains of old shore-lines at altitudes 

 so high above Lake Ontario, as to indicate that the same sheet 

 of water (Warren water) covered also the basins of the other 

 and higher lakes. After the dismemberment of this greater 

 sheet of water, the surface of that occupying the Ontario-St. 

 Lawrence valley was gradually lowered, and fell several 

 hundred feet, without pausing long enough to deeply cut out 

 or straighten its changing shore-lines. At last, this shrinkage 

 of the waters came to a pause lasting until the shore-line 

 became more pronounced than that of the modern lake. It 

 is this shore-line that forms the basis of the present chapter, 

 and constitutes that water-margin which the writer has named 



* The forerunner of this paper was — " The Iroquois Beach, a chapter in the 

 Geological History of Lake Ontario" — was first read before the Philosophical 

 Society of Washington, January, 1888. Proc. Phil. Soc. for 1888, and was subse- 

 quently amplified and published in full in the Transactions of the Royal Society 

 of Canada for 1889. 



f For reference to early writers, see "Iroquois Beach," etc., Transactions Royal 

 Society of Canada, 1889, page 121. 



