of Valleys and Lakes. 301 



peaks are tipped with perpetual snow. The Rhone glacier had 

 therefore no lack of tributaries to maintain its mass over all the 

 area of the Lake of Geneva, though towards the west, where the 

 glacier thinned away, that mass would be less than over the 

 eastern half of the lake, where weight and grinding-power must, 

 I believe, on that account have necessarily been greater. But 

 the main flow of the ice, after escaping from the Rhone valley, 

 was necessarily of a mixed nature, partly to the N.W., and also 

 to a great extent to the N.E. and S.W., simply because the N.W. 

 face of the glacier abutted on the Jura. For it requires no pro- 

 found knowledge of physics to perceive that any body, whether 

 actually plastic like pitch, or of a modified plasticity that may be 

 fractured and reunite like jelly*, or that by " fracture and regela- 

 tion " behaves like a plastic body, — I say it requires no profound 

 knowledge of physics to understand that such a body, constantly 

 renewed and pressed on from behind, when opposed by a high 

 impassable barrier (like the Jura), will spread itself out in the 

 direction of least resistance, that direction in the case of the 

 Rhone glacier having been at right angles to the general pres- 

 sure, or N.E. and S.W., whence I believe the general form and 

 trend of the Lake of Neuchatel. 



But, in the second place, is there indeed no proof that ice 

 " neither has nor has had any excavating power," whether in val- 

 leys of large or of low inclination, narrow or broad ? Then why 

 is it that all the rivers that flow from glaciers, great and small, 

 are so muddy ? Surely no one will contend that all " the flour 

 of rocks " that gives to the rivers a pipeclay colour has been 

 washed in by streams from the surface. Alpine club men who 

 drink (rarely) of the brooks that run on the surface of the ice 

 will repudiate the idea ; those who fancy they see in the Loess 

 of the Rhine the old glacier-ground mud of the Alps will shrink 

 from it j and many, if not all the Alpine geologists versed in ice 

 whom I have conversed with in Italy and Switzerland, will, I ven- 

 ture to say, still hold that glaciers by erosion seriously affect 

 their beds. What else is the meaning of the striation and deep 

 grooving, the mammillation and the glassy polish, even of quartz, 

 and of all the Alpine rocks, whether hard or soft ? The mud of 

 the rivers is chiefly derived from this incessant ice-waste; and that 

 is why it is so unearthy, so clean, fresh, and impalpable. Were it 

 merely or chiefly surface-wash, derived from the hills and washed 

 underneath and carried forward below the glaciers, the sediment 

 in great part would be dirty, torrential, and coarse enough, espe- 

 cially if, as is stated, glaciers do not seriously grind along their 

 rocky floors. So far from a glacier exercising only a trifling grind- 

 ing-power, " because it is usually separated from the subjacent 

 * I have obtained this comparison from the Master of the Mint. 



