CLOUDS AND EIVEES, ICE AND GLACIERS. 81 



plan, p. 83) a wall of ice about 150 feet "high has already 

 attracted our attention. Bending round to join the 

 Lechaud the Glacier du Geant is here drawn away from 

 the mountain side, and exposes a fine section. We try 

 to measure it top, bottom, and middle, and are defeated 

 twice over. We try it a third time and succeed. A 

 stake is fixed at the summit of the ice-precipice, another 

 at 4 feet from the bottom, and a third at 35 feet above 

 the bottom. These lower stakes are fixed at some risk 

 of boulders falling uj>on us from above ; but by skill 

 and caution we succeed in measuring the motions of all 

 three. For 24 hours the motions are : — 



Top stake 



. 6 inches 



Middle stake . 



. . ** .. 



Bottom stake . 



• 2§ „ 



202. The retarding influence of the bed of the glacier 

 is reduced to demonstration by these measurements. 

 The bottom does not move with half the velocity of the 

 surface. 



§ 29. Lateral Compression of a Glacier. 



203. Furnished with the knowledge which these 

 labours and measurements have given us, let us once 

 more climb to our station beside the Cleft under the 

 Aiguille de Charmoz. At our first visit we saw the 

 medial moraines of the glacier, but we knew nothing 

 about their cause. We now know that they mark upon 

 the trunk its tributary glaciers. Cast your eye, then, 



