CLOUDS AND EIVEES, ICE AND GLACIERS. 117 



strained portion of the glacier, where a crack is for me J 

 across the stream. A way is thus opened for the water 

 to the bottom of the glacier. By long action the stream 

 hollows out a shaft, the crack thus becoming the 

 si arting-point of a funnel of unseen depth, into which 

 the water leaps with the sound of thunder. 



296. This funnel and its cataract form a glacier Mill 

 or Moulin. 



297. Let me grasp your hand firmly while you stand 

 upon the edge of this shaft and look into it. The hole, 

 with its pure blue shimmer, is beautiful, but it is terrible. 

 Incautious persons have fallen into these shafts, a 

 second or two of bewilderment being followed by sudden 

 death. But caution upon the glaciers and mountains 

 ought, by habit, to be made a second nature to explorers 

 lil^e you and me. 



298. The crack into which the stream first descended 

 to form the moulin, moves down with the glacier. A 

 succeeding portion of the ice reaches the place where 

 the breaking strain is exerted. A new crack is then 

 formed above the moulin, which is thenceforth for- 

 saken by the stream, and moves downward as an empty 

 shaft. Here upon the Mer de Glace, in advance of the 

 Grand Moulin, we see no less than six of these forsaken 

 holes. Some of them we sound to a depth of 90 feet. 



299. But you and I both wish to determine, if possible, 

 the entire depth of the Mer de Glace. The Grand 

 Moulin offers a chance of doing this which we must not 



