Postglacial Stibm.ergence east of Georgian bay. — Taylor. 287 
northeast. The beach near Midland is about 22 miles west 
and ten north from Orillia. But its level is ten feet lower. 
This probably does not mean a northward descent from Oril- 
lia, but rather a strong eastward rise from Midland. From 
the locality near Lorneville to that near Midland is about 40 
miles west and 20 miles north; but the beach at Lorneville is 
five feet the higher. The beach at Barrie, however, is 40 feet 
below that at Midland, showing that the apparent absence of 
the northward rise is due to the obscuring effect of the east- 
ward rise. The same is probably the case between Midland 
and Orillia. The value of a comparison where the differences 
are small, however, is considerabl} T impaired if it depends on 
measurements made by aneroid barometer, as is the case with 
our work. 
From Orillia to North Ba} T the direction is nearly due north, 
and the intermediate places deviate but little from that line. 
The measurements of altitude are probably fairly accurate at 
all the places except Bracebridge, where the weather condi- 
tions were not good, and the margin of error may be somewhat 
larger. Taking the figures as we have them, the northward 
rise from Orillia to Bracebridge is a trifle over 4 feet per mile ; 
from Bracebridge to Huntsville, less than l^feet; fromHunts- 
ville to Sundridge, about 6 feet and 2 inches: from Sundridge 
to South River, about 3 feet; and from South River to North 
Bay, a northward descent of about 2^ feet per mile. 
Perhaps the most interesting result of these excursions was 
the finding of the great silt beds. When we take into ac- 
count all their relations to the adjacent glacial and postgla- 
cial deposits, the wideness of their distribution, and their 
remarkable uniformity of composition in all places, it seems 
impossible to miss their meaning. These deposits were found 
not only in the highlands < - ; i s t of Georgian hay as here de- 
scribed, but also at several other distant places. The}' were 
found at Superior opposite Duluth, and at Sault Ste. Marie: 
at many points along the Spanish ami White Fish rivers north 
of lake Huron ; all along the north side of lake Ni pissing, 
and up the valley of the Veuve ; at Pawassan, Trout (reck. 
South River, Burk's Falls, Huntsville and Bracebridge, on the 
line of the Northern and Pacific Junction railway; in the 
valley of the Oswegatchie river near Edwards and South Ed- 
