August 21, 1916. 
Canada 
Geological Survey 
Museum Bulletin No. 23 
GEOLOGICAL SERIES, No. 32. 
The Trent Valley Outlet of Lake Algonquin and the Deformation 
of the Algonquin Water-plane in Lake Simcoe District , Ontario. 
By W. A. Johnston. 
INTRODUCTION. 
Lake Algonquin has long been known to have been the 
largest of the glacial, ice-dammed lakes which existed in the 
Great Lake region of North America at the close of the ice age. 
This lake overspread the basins of Lakes Superior, Michigan, 
and Huron and a portion of the adjacent regions. In Lake 
Ontario basin another ice-dammed lake, known as Lake Iro- 
quois, existed. It has been generally inferred that Lake Iro- 
quois for at least a part of its existence was contemporaneous 
with Lake Algonquin. The probability of an outlet of Lake 
Algonquin near Kirkfield, Ontario, and the occurrence of an 
abandoned river channel, apparently connecting the two lakes, 
along the line of the Trent Valley chain of lakes and rivers, was 
first recognized by J. W, Spencer. In 1888, Spencer 1 proposed 
the name “Algonquin River” for this ancient river. Two years 
later he stated, however, that he had overestimated the im- 
portance of this outlet and considered that the outlet was in 
existence only at the highest level of Lake Algonquin.* In 
i Spencer, J. W., “Notea on the origin and history of the Great Lakes of North America” 
(Abstract); Proc. Am. Assoc, for the Ad. of Sc., vol. 37, 1888, pp. 198-199. 
* Idem. 
