342 J. O. Smock—Thickness of the Continental Glacier. 
coarse bowlder drift, modified and made from the destruction 
of the once continuous moraine. These sandstone ridges also 
were but partially covered by the glacier as it here neared its 
most southern extension. The elevation of the drift upon them 
varies from 700 to 900 feet. The highest points on the 
Schooleys Mountain table-land are the summits of the moraine 
hills, which are 1,200 to 1,300 feet above tide. And this is 
of the State. The glacier pushed southward in the red sand- 
stone plain and attained a latitude of 40° 30’, at the mouth 0 
the Raritan River. The most southerly point at which we 
have any record of it, in the Delaware Valley, was near Belvi- 
dere,—in latitude 40° 50’.. Both of these loops appear to have 
been thinner near their southern edges than the mass on the 
Highlands. The differences in elevation in these valleys and 
on the Highlands may give us the rate of increase in thickness 
from north to south. For example, at Dover the moraine 1 
22 miles north of the latitude of Perth Amboy, and the eleva 
tion at Dover is 640 feet. If at Amboy the ice was 
referred to above. Inequalities in the surface over which the — 
ice moved, differences in the rate of accumulation of the snows 
and ice as well as in that of its wasting away and its retreat 
