ICE AND GLACIERS. 



117 



the middle and after the union 

 of the three glaciers the depth 

 must be far greater. Somewhat 

 below the junction Tyndall and 

 Hirst sounded a moulin, that is 

 a cavity through which the sur- 

 face glacier waters escape, to a 

 depth of 1 60 feet ; the guides 

 alleged that they had sounded 

 a similar aperture to a depth 

 of 350 feet, and had found no 

 bottom. From the usually deep 

 trough shaped or gorge-like form 

 of the bottom of the valleys, 

 which is constructed solely of 

 rock walls, it seems improbable 

 that for a breadth of 3,000 feet 

 the mean depth should only be 

 350 feet ; moreover, from the 

 manner in which ice moves, there 

 must necessarily be a very thick 

 coherent mass beneath the cre- 

 vassed part. 



To render these magnitudes 

 more intelligible by reference to 

 more familiar objects, imagine 

 the valley of Heidelberg filled 

 with ice up to the Molkencur, 

 or higher, so that the whole 

 town, with all its steeples and 

 the castle, is buried deeply 

 beneath it ; if, further, you ima- 

 gine this mass of ice, gradually 

 extending in height, continued 

 from the mouth of the valley up 

 to Neckargemiind, that would 

 about correspond to the lower 



FIG. 15. 



