Mr. J. C. Moore on Lake-Basins. • 527 



angle of 5° than at one of 10°, &c. In fact the maximum will 

 be at 45° ; and this I believe to be in accordance with what takes 

 place in rivers with highly-inclined beds. At steep rapids the 

 erosion is considerable ; but when the angle becomes almost im- 

 perceptible, the river, so far from cutting down its bed, often 

 raises it by deposition of sediment. 



As soon as the glacier reaches the plain, erosion by sliding 

 ceases ; and if it moves, it must be by propulsion ; and if it ex- 

 cavates, the materials ground down must be removed. It is 

 difficult to conceive how this can have been effected but by run- 

 ning water ; and that is contrary to the idea of a rock-basin. In 

 those cases where a glacier has been seen to be forced up a slope, 

 is it certain that the rock with the same slope extended quite 

 across the valley ? May not one side of the bottom of the valley 

 have been higher than the other ? so that while the ice was forced 

 up the slope on one side, the rest of the glacier with water issuing 

 from under it may have been sliding down the other side. But if 

 there is to be no river, then how were, say, the last 100 feet of 

 depth of the Lake of Geneva excavated ? It is not " le premier 

 pas qui coute," but " le dernier." Even granting that the enor- 

 mous mass which the problem supposes could be forced up a 

 slope, what becomes of the fine fluid mud into which the rocky 

 contents of the lake had been ground ? The advancing face of 

 the glacier cannot be presumed to have forced the water before 

 it, for it is fissured in all directions ; and though a glacier is said 

 sometimes to thrust pebbles before it, the watery mud would 

 always subside into the depths. 



Professor Ramsay, in his memoir published last October, 

 admits that a quasi-plastic body constantly pressed from behind, 

 when opposed by a high impassable barrier like the Jura, would 

 spread itself out in the direction of least resistance. On this I 

 would observe that it was not the height of the Jura which 

 formed the impassable barrier : the glacier merely felt the re- 

 sistance of a rock at its own level, and, in obedience to the law, 

 which I cordially accept, turned aside in the direction of least 

 resistance. And on the same principle I should expect the 

 Rhone glacier, on issuing from the gorge, to crawl along the 

 plain, as glaciers are known to do, instead of seeking out resist- 

 ance by burying itself 1000 feet among hard rocks. 



