GLACIAL STUDIES LY GREENLAND 233 



with the trunk of the Tuktoo glacier, as already observed. Below 

 this it rubs hard against the Sierra and Sentinel nunataks and 

 its activity is such as to prevent the development of the fossae 

 which often lie between nunataks and adjacent glaciers. Between 

 the two nunataks named the glacier protrudes westward to meet 

 the reciprpcal eastward protuberance of the Tuktoo glacier, and 

 the two jointly impound two small triangular lakes in the angles 

 between themselves and the nunataks. Where the protuber- 

 ances are opposite to each other their extremities are not verti- 

 cal, though steep and somewhat stepped. This is perhaps due to 

 the absence of the reflecting frontal plane which I have thought 

 might be one of the factors in the development of the ver- 

 tical faces. Each glacier standing opposite to the other covers 

 the ground which would otherwise act as a reflecting surface. 



On the east side of the Bowdoin glacier, however, there is 

 the usual vertical face with its accompanying sharp triangular 

 valley between the ice and the adjacent rock slope. This 

 extends from the extremity of the glacier to the point of its 

 junction with the East Branch glacier, a distance of perhaps 

 three miles. At a few points spurs of rock close the valley. East 

 Branch hill projects notably into the path of the glacier and not 

 only closes the lateral valley but crowds the border of the ice 

 out of its path. At these points of interruption the stream, 

 which as usual runs between the glacier and the valley 

 side, is forced to tunnel under the glacier. After a cold day or 

 two, the water in the stream becomes low and the tunnels then 

 afford a means of penetrating to limited distances beneath the 

 ice. Fig. 66. The phenomena so disclosed, however, do not 

 essentially differ from those seen to better advantage in the ver- 

 tical sides. The amount of debris appears more scant because 

 it is not concentrated by surface melting nor exaggerated by 

 surface wash. In some instances where blocks of ice had recently 

 fallen away from the roof, opportunity was given for the study 

 of exceptionally fresh unweathered ice which had not been sub- 

 jected to the sun's rays, except as they reached it through con- 

 siderable depths of ice. Even here the ice is far from being 



