LAKE ALGONQUIN. 
19 
tude of the beach was determined and the distances between 
these points were secured. The altitudes are all instrumental 
determinations and so far as the actual levelling is concerned, 
they are believed to be correct within a possible error of one 
foot, except in the case of the three most northerly ones which, 
because of the distance over which the levels were carried, may 
not be so nearly correct. 
It is not held that the profile shows the exact character of 
the warped water-plane, for it is recognized that the altitudes of 
the shore-line do not truly represent the altitudes of the water- 
plane. The altitudes are all, however, of wave-built features 
such as beach ridges, barrier beaches, etc., and the exposure to 
wave action was fairly uniform throughout the area, so that 
there is likely to be a fairly close agreement between the alti- 
tudes of the beaches and the altitudes of the water-plane. It is 
considered that the difference at any one locality due to the great- 
er or less development of the shore features and errors in level- 
ling would not exceed 5 feet. 
The profile shows that there is at least one locality in the 
district where there is a marked irregularity in the rate of uplift. 
Between Beaverton and Lorneville the beach rises from 824 
to 838 or 14 feet in a distance of 1A miles. If the altitude 838 of 
the beach is accepted, the beach rises 14 feet in less than one-half 
mile. The altitude of the beach as determined at this point 
may, however, be too high and it need not be taken into con- 
sideration. South of Beaverton the altitudes of the beach show 
a rise of only 8 feet in a little over 5 miles. North of Lorneville 
the beach rises 7 feet in 2 \ miles. The marked increase in the rate 
! of rise of the beach between Beaverton and Lorneville is too 
great to be accounted for by greater development of the beach 
at one point than at another. The field evidence also shows that 
this is not the case. The sudden increase in the rate of tilt at 
this point is confirmed by the altitudes of the beach along the 
same isobases on the opposite side of Lake Simcoe, where the 
beach rises 14 feet in 1| miles. The beach can be traced con- 
tinuously at these localities. No evidence of faulting was seen 
and the sudden increase in the rate of tilt is apparently due to 
local warping. The irregularity in the profile between Beaverton 
