600 A. W. G. WILSON SHORELINE STUDIES ON ONl'ARlO AND ERIE 



possibly no beach at all. Thus, from the general assemblage of shore 

 features found on these lakes, their shores would be classed as adolescent.* . 



Comparison of modern Ontario and glacial Lake Iroquois 



An extremely interesting comparison can be drawn between the shores 

 of lake Ontario and those of its predecessor, glacial lake Iroquois. The 

 shores of lake Iroquois presented lines of sea-cliffs similar in nearly every 

 respect to those of the present lake; barrier beaches were built across 

 open bays; one of these still retains its lagoon as a small pond, known 

 as Silver lake, near Colborne, Ontario.'' Flying spits were thrown out 

 from salient points and belts of dunes behind sand beaches were built as 

 on the present lake. An almost exact counterpart of Toronto island is 

 found in an Iroquois flying spit near York, and another in the Daven- 

 port gravel ridge north of Toronto. At the west end of lake Iroquois a 

 strong barrier beach was built across the valley between the limestone 

 escarpments, cutting off what is now the Dundas marsh from the main 

 lake, counterparts of the present Burlington beach and bay. 



On the south shore similar bars and spits have been noted. One of 

 them, near Pultneyville, New York, was a flying spit similar to that at 

 Scarboro, but pointing eastward. 



The type of shore developed on lake Iroquois was very similar to that 

 developed on lake Ontario at the present time, and would be classed as 

 adolescent. Since the disappearance of- lake Iroquois, subaerial erosion 

 processes have only slightly modified the abandoned adolescent shore- 

 lines. Slips on the sea-cliffs have obscured old beaches ; winds and rains 

 have variously modified the old dunes and sand beaches. All the old 

 sea-cliffs are graded to the summit, but in a few cases even yet an occa- 

 sional slip may occur under special conditions. The original forms of 

 adolescence, while not yet destroyed, are gradually fading and sequential 

 forms of subaerial origin are developing. 



In conclusion, the writer wishes to express his obligations to Professor 

 Alfred J. Henry for the tracings from which figures 6 and 7 were pre- 

 pared and for copies of the two bulletins of the United States Weather 

 Bureau referred to in the text. He is also indebted to Mr James White, 

 Chief Geographer of the Department of the Interior, Ottawa, for tracings 

 from which the figures of Long point, Point aux Pines, and point Pelee 

 were drawn. The balance of the figures are traced either from govern- 

 ment maps or were photographed by the author. 



• GulUver : Shoreline topography. Proceedings of the American Academy of Arts and 

 Science, vol. xxxlv, 1899. 



' Coleman : Lake Iroquois, 13th Annual Report, Bureau of Mines, Ontario, 1904. 



