368 Glaciers. 



result is that, let the rock be ever so hard, it is in 

 places polished almost as smooth as a polished agate, 

 and this surface is also finely striated and coarsely 

 grooved by the debris that, imprisoned between the ice 

 and the rocky floor, is pressed along in the direction 

 of the flow of the ice. By degrees deep furrows are 

 sometimes thus cut in the rocks. 



But the stones that are imprisoned between the ice 

 and the rocky floor not only groove that floor, but in 

 turn they also get scratched by the harder asperities 

 of the rocks over which they are forced ; and thus it 

 happens that many of the stones of moraines are covered 

 with straight scratches, often crossing each other 

 irregularly, so that we are able by this means to tell, 

 independently of the forms of the heaps, whether such 

 and such a mass is a moraine or not, and indeed, under 

 any circumstances, whether certain stones have been 

 acted on by glacier ice. 



These indications of the rounding, smoothing, scratch- 

 ing, and grooving of rocks, in lines coincident with the 

 direction of the flow of glaciers, together with moraine 

 heaps, erratic blocks, and scratched stones, are so charac- 

 teristic of glaciers, that we are able to establish the 

 important fact that the Swiss glaciers were once of far 

 larger dimensions than they are now, and have gradually 

 retreated to their present limits. For example, all 

 down the Valley of the Ehone, from the end of the 

 Ehone glacier to the Lake of Geneva, mammillated 

 rocks (moutonnee), moraine-mounds, and great erratic 

 blocks, are of frequent occurrence, a notable case oc- 

 curring on the slopes behind Monthey, sone sixty 

 miles below the source of the river, where the ' blocks 

 of Monthey ' have long been celebrated. Fifty miles 

 beyond that, the same great glacier that filled the 



