58S T. C. CHAM BERLIN 



streams that issue on the face of the glacier in the center of the 

 figure. These follow the crevasses until they reach the face of 

 the glacier, when they descend it vertically. (It may be 

 remarked in passing that the whiteness of the track of these 

 little streams as they descend the side of the glacier indicates 

 the relative purity of the ice. The blackened, unwashed surface 

 shows the extent to which the fine debris, when freed by slow 

 melting, covers the surface and invites an illusive impression of 

 its amount.) Fig. 6i, from a larger photograph taken by Pro- 

 fessor Libbey, shows more satisfactorily both the normal, gaping 

 crevasses and these unopened crevices, and displays at once their 

 differences in nature and in direction. By inspection of this 

 figure it will be seen that these crevices extend to depths quite 

 comparable to those reached by the crevasses, though they are 

 individually less persistent. It will be observed that they usually 

 terminate at a bedding line or at a fellow crevice and that they 

 very much resemble the jointing of certain tilted rock beds. In 

 some instances faulting appears to be indicated. 



As remarked in the case of the upper Blase Dale glacier, the 

 stress or tension which caused these crevices was not of such a 

 nature as to require the gaping of the crevice after it was formed. 

 In this respect, as well as in their direction, they differ from 

 normal crevasses. It will perhaps be best to reserve a discussion 

 of the cause and significance of the phenomenon until the 

 remaining glaciers are described and the general subject of 

 interpretations and inferences is taken up. 



The two photographs show imperfectly a horizontal lining or 

 ridging of the retreating surface of the glacier above the vertical 

 face. These lines really represent a series of small terraces, the 

 vertical faces of which rise a foot or so in height and the upper 

 faces of which range up to a dozen feet in width. These terraces 

 are really the obliquely outcropping edges of the glacial strata 

 and are developed into the terrace form by differential melting 

 of the ice, much as steps in stratified rock are developed by dif- 

 ierential erosion. Their attitude is due to the upward curving of 

 the layers of ice as they come to the surface, in accordance with 



