GLACIAL DRIFT. 261 
nying heliotype. The two upper figures show the opposite sides of the 
same pebble—nearly of the natural size—of a mica slate, not of remote 
origin. On one side the striz run at a small angle with the longer axis 
of the pebble. On the reverse side the lines are irregularly disposed. 
The lower left-hand view shows an argillaceous schist, derived from 
ledges five or six miles distant, of oblong shape, three inches long, and 
the striae on both sides are approximately parallel to the longer axis. 
The whole surface on every side has been glaciated, some of the depres- 
‘sions being deeper than the others. The other view is of a Huronian 
schist, derivable from ledges three to twenty miles away, 12 inches long, 
7 wide, and 3 thick. The upper end has been partially encrusted with 
carbonate of lime of more recent origin than the striz. The opposite 
flat sides are scratched parallel to each other, and the longer axis of the 
stone. The ends are rough. This represents the shape and peculiarity 
of the striation of a majority of glaciated boulders. 
The following varieties of material have been found in company with 
these heliotyped boulders upon the north side of Mink brook, about a 
mile east of the brick church at Mill Village: Hornblende schist, dia- 
base, blue and gray quartzite, clay slate, serpentine, red quartz, red sand- 
stone, and gneiss. The cliff is 4o feet high, the upper ten feet of upper 
till containing limestone. 
These boulders must have been brought by the south-east current, 
some of them 65 or 70 miles. I think there is a notable absence of the 
Bethlehem gneiss among them. In the north part of the town the drift is 
very thick on the northern slopes. On following Mink brook to its source, 
in the south-east corner of the town, other similar ground-moraines occur. 
The same are more abundant south of Hayes hill in the edge of Leba- 
non. A tributary of the Mascomy has cut through this deposit, produc- 
ing by erosion terraces of till. The surfaces of all these moraines are 
smooth, indicating the sliding of a glacier over them. Between Prospect 
and Corey hills is a smooth depression rising gradually to the curved 
water-shed between the stream flowing west and Mink brook. Scarcely 
any boulders occur on this basin; but after beginning the descent to Mill 
Village, coarse moraines and large rough boulders, twelve and fifteen feet 
through, abound. It would seem that the glacier broke off the fragments 
from the ledges of the smooth area, carried them to the brink of the 
VOL, Ill, 34 
