CLOUDS AND RIVERS, ICE AND GLACIERS. 



109 



of partially indurated mud, you may sometimes notice 

 appearances similar to those exhibited by the ice. 



SKETCH OF CURVED CREVASSES : THE GLACIER MOVES FROM LEFT TO RIGHT. 



§ 41. Longitudinal Crevasses. 



276. We have thus unravelled the origin of both 

 transverse and marginal crevasses. But where a glacier 

 issues from a steep and narrow defile upon a com- 

 paratively level plain which allows it room to expand 

 laterally, its motion is in part arrested, and the level 

 portion has to bear the thrust of the steeper portions 

 behind. Here the line of thrust is in the direction of 

 the glacier, while the direction at right angles to this 



