4 
MUSEUM BULLETIN NO. 23. 
present altitude of the ancient water-plane. Hence a detailed 
study of the raised beaches in this district affords data 
which are of value in determining the character and amount of 
the differential uplift which deformed the beaches. 
The relation in time of Lake Algonquin and Lake Iroquois 
is of considerable importance in connexion with a study of the 
differential uplifts. In order to determine this relation, measure- 
ments of the altitudes of the raised beaches along the Trent 
valley and an examination of the outlet channel as a whole, for 
which no satisfactory interpretation has been given, were neces- 
sary. 
The object of the present paper is to present the results of a 
detailed survey of the Algonquin beach in Lake Simcoe district, 
Ontario, and of its correlatives along the line of the Trent Valley 
chain of lakes and rivers, and hence to attempt to show the 
relation of Lake Iroquois to Lake Algonquin. In Lake Simcoe 
district the altitude of the Algonquin beach has been accurately 
determined at close intervals. By means of these altitudes a 
map showing isobases or lines of equal deformation of the Algon- 
quin beach and a profile of the warped Algonquin water-plane, 
along the line of maximum uplift, have been constructed, by 
which an attempt is made to show the approximate character of 
the differential uplift which has affected the region during and 
since the existence of Lake Algonquin and its correlatives. 
SHORE-LINES OF LAKE ALGONQUIN AND ITS CORRELATIVES, AND 
ALGONQUIN RIVER. 
Lake Simcoe and Balsam Lake Districts. 
In Lake Simcoe and Balsam Lake districts, Ontario, the 
following instrumental measurements of the highest Algonquin 
beach were made in 1908 by Goldthwait, Taylor, and the writer; 1 
i Goldthwait, J. W., Geol. Surr., Can., Mem. 10. 
