128 



ICE AND GLACIERS. 



FIG. 21. 



partly by the weathering of 

 the stone, and partly by the 

 freezing of water in its crevices, 

 they fall, and for the most part 

 on the edge of the mass of ice. 

 There they either remain ly- 

 ing on the surface, or if they 

 have originally burrowed in 

 the snow, they ultimately re- 

 appear in consequence of the 

 melting of the superficial 

 layers of ice and snow, and 

 they accumulate especially 

 at the lower end of the gla- 

 cier, where more of the ice 

 between them has been 

 melted. The blocks which are 

 gradually borne down to the 

 lower end of the glacier are 

 sometimes quite colossal in 

 size. Solid rocky masses of 

 this kind are met with in the 

 lateral and terminal moraines, 

 which are as large as a two- 

 storied house. 



The masses of stone move in 

 lines which are always nearly 

 parallel to each other and to 

 the longitudinal direction of 

 the glacier. Those, therefore, 

 that are already in the middle 

 remain in the middle, and 

 those that lie on the edge re- 

 main at the edge. These latter 

 are the more numerous, for 

 during the entire course of the 

 glacier, fresh boulders are COD- 



