GLACIERS 215 
sheets of ice, there are no moraines upon the surface, 
for no rocks rise above it to furnish debris. But be- 
neath the ice there is probably a ground moraine 
(Fig. 120), and we are certain that terminal moraines 
are being constructed at the margin. 
Fie. 120. 
The margin of the Bowdoin glacier, showing ground moraine in the base of the 
ice cliff. 
The continental glacier also differs from the smaller 
valley glaciers in not being confined to valleys, but in 
moving over the country, in a measure regardless of 
the topography. There is a resemblance between the 
two classes of glaciers in the slow movement and the 
