306 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
which reaches a trunk stream at C, while ADC is the profile of an 
adjoining lateral spur. After vigorous and mature glaciation, the 
dotted line, GE, may represent the surface slope of a lateral glacier, 
and GHJ that of the lateral glacier bed; while EFL is the surface 
of the trunk glacier, and EKL the bed. The lower part of the 
lateral spur has been cut off to make the basal cliff beneath D. On 
the disappearance of the trunk glacier at this stage, the shrunken 
side glacier, GNJJI, occupies its corrie or hanging valley, which 
opens at J on the oversteepened wall, D JK, of the evacuated channel 
of the trunk glacier. Let the maximum erosion of the corrie glacier, 
as conditioned by pressure and motion, be at H. Then after some 
time the weathering of the cliff walls and the erosion of the Boor 
will have transformed the corrie and its glacier to a form, 
G'N' J'H', such that the deepening of the glacial bed should be a 
maximum at HH'. The continuous slope of the glacial bed, GHJ, 
appropriate to the time when the lateral glacier joined the trunk 
glacier, may thus be transformed into a basined curve, G' H'J', 
appropriate to a small glacier terminating at J'; and on the disap¬ 
pearance of the small glacier, a tarn or rock-basin lake may occupy 
the depression at IT. It is on the basis of a supposition like this 
that a determination has been attempted of the altitude at which 
the shrinking remnants of an extensive glacial system endured for 
a time before their entire disappearance (J. Geikie, ’ 98 , 233). 
Richter’s supposition that the uplands of Norway result from the 
