EXPERIMENTS IN ICE MOTION. 933 
It will be seen how currents might rise from the bottom of Lake 
Ontario passing in an arch over the drift-covered region south of 
the lake and then descend to aid in the excavation of the bed of 
Cayuga Lake. 
The minor irregularities of the Medina conglomerate, border- 
ing this portion of the shore of Lake Ontario, produced minor 
and differential currents in bottom of the great arch and formed 
thedrumlins. This diagram would apply with slight modifications 
of detail to a large majority of the known drumlin regions. 
— Temas .€ Ca song: 
AS feeg 2 — 
Interne 
The formation of the elongated drumlins may find an 
explanation in the stretching out of the débris into the ice from 
the top of an obstruction. If toward the end of the glaciation the 
drift should become of sufficient thickness, it might in spots clog 
up under the ice and become sufficiently resistant to cause upward 
currents in the ice. Its face would be moulded to its steeper 
form by the minor currents which creep up the face of an escarp- 
ment or obstruction (Expt. 2, Fig. 2), and are perhaps responsi- 
ble for the characteristic steeper slope of the face of all sub- 
glacial erosion forms. The currents of inthrust débris would 
arise from the heaps of débris and extend forward into the ice 
a short distance, while still under the arch of the currents they 
would gradually sink and build up the rear of the drumlin into 
the elongated form. The elongation and building up of the 
drumlin would tend to keep the currents from descending and 
would lengthen the arch till drumlins two miles long might be 
formed as noted in New York. 
One other action must be noticed, namely, the moulding 
power of the ice currents upon a thick sheet of till. It has been 
