20 
MUSEUM BULLETIN NO. 23. 
and Lorneville and possibly at two other localities, viz., north 
of Wilfrid and north of Kirkheld, contrasts with the even char- 
acter of the profile south of Wilfrid. At all three localities the 
over-steepened portions of the profile are preceded and followed 
by more nearly horizontal portions. The evidence suggests that 
the character of the deformation is that of differential warping. 
The rate of uplift increases towards the north but is interrupted 
by local irregularities. Because of errors involved, however, 
in assuming that the altitudes of the beaches truly represent the 
altitudes of the water-plane it does not seem possible to demon- 
strate what was the exact character of the epeirogenic movements 
which deformed the ancient water-plane. 
The deformation of the highest Algonquin beach forms a 
record of the differential uplift which took place during the exist- 
ence of the lake and after its disappearance. It is probable, as 
Taylor has pointed out, that uplift took place, also, previous to 
the inception of Lake Algonquin, so that the tilt rate as shown on 
the accompanying map and profile does not represent the total 
amount of uplift. It is probable, however, that the earlier up- 
lifts affected more particularly the southern portion of the 
Great Lake region and that there was a * ‘northward migration 
of the zone of deformation/’ 1 This is shown in Lake Simcoe 
district by the marked change in the direction of maximum 
uplift and by the rapid increase in rate. The northward migration 
of the zone of deformation or wave of uplift proceeding from south 
to north, taken in conjunction with the probability that the 
highest Algonquin beach in the southern portion of the Great 
Lake region is a transgressional beach, that is it represents a 
long still-stand of the waters following a rise due to uplift of the 
northern part of the basin, explains why the highest Algonquin 
beach is practically horizontal over a considerable part of the 
southern portion of the Great Lake region. 
SUMMARY. 
The ancient Algonquin river or outlet channel of Lake 
Algonquin, along the line of the Trent Valley chain of lakes 
and rivers, began at Fenelon Falls and not at Kirkfield as has 
* Goldthwait, J. W., Wisconsin Survey Bulletin XVII, p. 115. 
