112 Mr. H. H. Howorth 



on 



theory. " The mass of the glacier," he says, " is in inverse 

 proportion to the slope over which it flows. When the 

 trough is steep, the ice is thin, and its surface is contracted ; 

 when the slope decreases and approaches to the horizontal 

 line, the glacier fills out — it becomes like a sea, or a lake 

 between two streams. . . . Nothing shows better to what an 

 extent the glacier adapts itself to the spot on which it 

 happens to be than the form of the glacier of Mont Dolent, in 

 the valley of Feriet." The highest plateau is a great amphi- 

 theatre surrounded by lofty flakes of granite of pyramidal 

 form ; thence the glacier descends by a gorge, into which 

 it is compressed ; but as soon as it has passed beyond it, it 

 widens out anew and opens like a fan: it has therefore, as a 

 whole, the form of a sheaf contracted in the middle and spread 

 out at the two extremities ( Voyage dans les Alpes, II. 247). 

 ^' There are a host of facts that would seem to induce the belief 

 that the substance of glaciers enjoys a kind of ductility which 

 allows it to mould itself upon the locality which it occupies — 

 to thin out, to swell, to contract, and to spread as a soft 

 paste would do. Nevertheless, when we deal with a piece 

 of ice, when we strike it, we find in it a rigidity which is in 

 direct opposition to the appearances of which we have just 

 spoken. Perhaps experiments made upon larger masses 

 would give other results" {Rendu, trans, by A. Wills, edited 

 by J. Forbes, 70 — 71). 



Again, the same author writes, "The fact of motion 

 exists, the progression of glaciers is demonstrated ; but the 

 mode of motion is entirely unknown. Perhaps with long 

 observations, with experiments upon ice and snow carefully 

 made, we shall succeed in grasping it ; but we are still in 



want of first elements Nothing seems to me more 



clearly demonstrated than the progressive motion of glaciers 

 towards the bottom of the valleys, and nothing at the same 

 time seems to me more difficult to conceive than the manner 

 in which this movement is executed — a movement so slow, 



