780 ROLLIN D. SALISBURY 



of the glaciers in many cases approximately vertical, but the 

 higher parts often overhang the lower (Figs. 3, 4, and 5). The 

 overhang is of different types. In general it seems to be true 

 that the overhang is dependent upon something in the structure 

 or constitution of the ice. (i) Where the ice is made up of 

 layers of unequal firmness, the more compact layers are likely 

 to project out over the more granular layers beneath (Fig. 3). 

 (2) Where there are layers of debris in the ice, the ice imme- 

 diately above is likely to overhang the debris-bearing layer 

 (Figs. 4 and 5). The overhang is usually the more pronounced 

 the larger the amount of debris. Since the lower fourth, third, 

 or half of the ends and edges of glaciers, as seen in section, is 

 often full of debris, the upper half, two-thirds, or three- fourths, 

 often overhangs the lower portion, as shown in Fig. 10. 



Where the debris is in very thin zones between thin layers of 

 ice, the overhang sometimes takes on a different phase. Here 

 the appearance is such as to suggest that a given layer of ice has 

 been shoved out a little over the next underlying (Fig. 11). On 

 close examination of the ice where the photograph reproduced 

 in Fig. 1 1 was taken, it was found in every case where one 

 layer appeared to have shoved out over its subjacent neighbor, 

 that the junction between the two was marked by a thin zone 

 (or film) of debris. In some cases the overhang, after persist- 

 ing laterally for some feet, ceased for the space of a foot or two 

 or more (see Fig. 12), to be continued again beyond. This was 

 sometimes repeated frequently along the contact of the layers. 

 If the phenomenon in question were really the result of the 

 shoving of an upper layer of ice over the one beneath, it would 

 hardlv be true that the movement would fail for a few inches 

 (as at be, de,fg, etc.. Fig. 12) at frequent intervals. On cutting 

 back into the face of the ice where this phenomenon of inter- 

 rupted overhang was seen, it was found, in every case where the 

 point was tested, that where the overhang failed, the debris 

 between the layers also failed, and that the amount of overhang 

 all along was in a general way proportional to the amount of 

 debris. 



