368 A. P. COLEMAN — IROQUOIS BEACH IN ONTARIO 



mation in a direction north 20 degrees east of the latest beach from 

 Hamilton to York, near Toronto, is 2 feet per mile ; from York to Quays, 

 near Port Hope, where the beach begins to split up, 3.4 feet per mile, 

 and from Quays to the West Huntingdon island, the last point where 

 the beach has been observed, it is 4.17 feet per mile, if the average of 

 the lowest well denned beaches of the series is taken as its continuation. 

 The splitting up of the beaches between Quays and Trenton is at the 

 rate of 3 feet per mile, but beyond this toward the northeast the highest 

 beaches are uncertain or may be entirely absent. 



Continuing the division of the highest and lowest beaches southwest 

 of the isobase passing through the Rome outlet, and assuming a separa- 

 tion proportional to the amount of deformation in that part of the old 

 shore, the lowest beach at Hamilton must have been 139 feet below the 

 highest, or 23 feet below the surface of lake Ontario. 



At the rate of differential elevation of 0.42 per 100 miles per century, 

 lake Iroquois lasted from 30,000 to 55,000 years, and the whole period 

 from its beginning to the present can not be less than 100,000 years ; 

 but the rate may have been more rapid at earlier stages, diminishing 

 the necessary time. Seven thousand years are, however, entirely too 

 short a time for the events since lake Iroquois began, and even 35,000 

 are scarcely long enough. 



The climate was probably cold temperate or subarctic, and the ice- 

 dam melted very slowly from the Saint Lawrence valley, though already 

 greatly thinned toward the northeast and nearly stagnant at the edge. 



