GLACIAL EROSION AND TRANSPORTATION. 267 



Fig. 80.— Section of east and west glacial furrows, on Kelly's Island. Till rests imme- 

 diately on the rock, with washed pebbles at the surface. 



The following very important extracts concerning glacial 

 erosion, from the recent report of Mr. I. C. Russell, need 

 no introduction and no comment : 



That the rock-basins in the high Sierra were excavated by 

 glaciers the writer finds no reason whatever to question. They 

 frequently occur at the lower limit of a steep slope, which is 

 polished and grooved, and bears every indication of having 

 been abraded by glacial action. In such cases the slope and 

 the direction of the furrows show that ice once descended into 

 the basin. On examining the opposite portion of the rim of 

 the depression, glacial markings of the same character will be 

 found. The proof is thus positive that the ice descended into 

 the depressions now filled with water, and emerged from them 

 again to continue its course. As there is no other agent known 

 capable of eroding hollows in solid rock having the character 



