THE FORMATION OF SOIL. 59 



" When we consider the weight of glaciers and their un- 

 yielding nature as compared with water, it is easy to see that 

 their erosive power must be very great. This is increased 

 immensely by fragments of stone of every conceivable size 

 carried along between the glacier and its bed. These partly 

 fall in at the sides and become jammed between the glacier 

 and the confining rocks, partly fall into the crevasses and work 

 their way to the bed, and partly are torn from the rocky bed 

 itself. The effects of glacier erosion differ entirely from those 

 of water : 1. Water, by virtue of its perfect fluidity, wears away 

 the softer spots of the rock and leaves the harder standing in 

 relief; while a glacier, like an unyielding rubber, grinds both 

 hard and soft to one level. This, however, is not so absolutely 

 true of glaciers as might be supposed. Glaciers, for reasons to 

 be discussed hereafter, conform to large and gentle inequalities 

 of their beds, though not to small ones, acting thus like a very 

 stiffly viscous body. Thus, their beds are worn into very re- 

 markable and characteristic smooth and rounded depressions 

 and elevations called roches mouton'ees. Sometimes large and 

 deep hollows are swept out by a glacier at some point where 

 the rock is softer, or where the slope of the bed changes sud- 

 denly from a greater to a less angle. If the glacier should 

 subsequently retire, water accumulates in these excavations 

 and forms lakelets. Such lakelets are common in old glacier 

 beds." 



Geikie thus describes the formation of soil in 

 his " Text-Book of Geology," * on page 339 : 



* Eeprinted, by permission, from " Text-Book of Geology," 

 by Archibald Geikie, LL.D., F.B.S, Director of the Geo- 



