FULLER : NOTES ON A CARBONIFEROUS BOULDER TRAIN. 263 
the slowness with which the pebbles become englacial, the ice 
taking them up gradually, and also in part to the fact that consid¬ 
erable distances are necessary in order that the pebbles become 
by the internal movements of the ice sufficiently elevated above the 
base to come within the influence of the streams forming the sand 
plains. 
Owing to the nature of the country few observations could be 
made as to the elevations attained by englacial drift within the ice. 
In the plains just north of the point where North St., Randolph, 
crosses the railroad (represented by shaded area marked S on 
the map) numerous pebbles were found at an elevation of 170 feet 
A T. The elevation of the top of this plain above the rock on 
which it rests is some 50 feet, and, as the plain was, with little 
doubt, derived from superglacial or englacial streams, it points to 
movements within the ice by which pebbles have, in a distance 
of about two miles, become elevated fifty feet or more from the 
base of the ice. The elevation of the ledges from which the peb¬ 
bles were derived is somewhat doubtful, as they are found at all 
elevations from 100 to 200 or more feet A T; but whatever may 
have been the height at which the pebbles were taken, it is evident 
that they were truly englacial. 
