: _ GLACIAL STUDIES IN GREENLAND. 67 
noted farther northward—the construction of a causeway by the 
glacier through the accumulation of its own débris beneath it. 
In their upper parts the glaciers appear to fit snugly in their 
respective valleys, and they doubtless have carried along with 
themselves all débris that may have been loosened beneath them ; 
but on reaching the lower gradients near the sea level much of this 
has been deposited, so that they are now creeping out on embank- 
ments of their own construction. It is perhaps not necessary to 
Fic. 16.—Distant view of a part of Petowik glacier. Ice mass in foreground 
showing cavernous melting at former water-line with subsequent tilting. 
suppose that they have built these up actually beneath themselves, 
as they may have constructed them by successive terminal 
deposits. When shorter than they now are they may have thrown 
down their material at their front edges, and subsequently have 
advanced upon it, building out the terminal accumulation in front 
as they slowly advanced. Whatever be the explanation (and 
passing observation gave no data for determining the mode of 
construction ), the interesting fact remains that the glaciers become. 
subservient to their own accumulations, instead of forcing them 
bodily out of their way. 
Near the western extremity of the Crimson Cliffs there stands, 
