CLOUDS AND RIVERS, ICE AND GLACIERS. 103 



greater depth and weight, or their less perfect attach- 

 ment, are compelled to move more quickly. A pull is 

 therefore exerted, tending to separate the lower from 

 the ripper snow. For a time this pull is resisted by the 

 cohesion of the neve; but this at length gives way, 

 and a crack is formed exactly across the line in which 

 the pull is exerted. In other words, a crevasse is formed 

 at right angles to the line of tension. 



§ 39. Transverse Crevasses. 



262. Both on the neve and on the glacier the origin 

 of the crevasses is the same. Through some cause or 

 other the ice is thrown into a state of strain, and as it 

 cannot stretch it breaks across the line of tension. Take, 

 for example, the ice-fall of the Geant, or of the Talefre, 

 above which you know the crevasses yawn terribly. 

 Imagine the neve and the glacier entirely peeled away, 

 so as to expose the surface over which they move. 

 From the Col du Geant we should see this surface 

 falling gently to the place now occupied by the brow of 

 the cascade. Here the surface would fall steeply down 

 to the bed of the present Glacier du Geant, where the 

 slope would become gentle once more. 



2C3. Think of the neve moving over such a surface. 

 Tt descends from the Col till it reaches the brow just 

 referred to. It crosses the brow, and must bend down 

 to keep upon its bed. Realise clearly what must occur. 

 The surface of the neve is evidently thrown into a 



