198 Rev. T. G. Bonneij — Notes on Glaciers. 



times stated, it seems to me very difficult to reconcile tlie great 

 erosive power attributed to glaciers with a great till-productive 

 power, when overriding their terminal moraines and the rubbish in 

 the lower valley. Some facts which I noticed last summer appeared 

 to have an important bearing on this question. At the present 

 time, the end of the Glacier des Bois just reaches the level bed of 

 the Arve valley, and reclines on ice-worn rocks, with its extremity 

 fitted into a sort of glen or ravine, not more than about thirty yards 

 across. Below it there is a stony plain covered with the usual mixture 

 of rounded and angular blocks — mica-schist, gneiss, protogine, etc. 

 Among these, a short distance from the end of the glacier and rather 

 near the left bank of the valley, is a huge block of protogine about 

 12 X 8 j^ards area and 4 high. The top of this, and to some extent 

 the sides also, are striated by ice mo^dng in the direction of the 

 present glacier. The Glacier of Argentiere is in a nearly similar 

 position ; about the last fifty yards rests on the stony bed of the Arve 

 valley, the remainder lies on rocky slopes. In front of it there is an 

 extensive area, now covered with boulders, which, within the last 

 few years, has been abandoned by the ice, and is inclosed by a com- 

 paratively fresh terminal moraine. Many of the smaller blocks on this 

 area, now almost concealed by rubbish scattered from the retreating 

 glacier, are smoothed and striated as if by passing ice, but the general 

 uniformity, however, of their upper surface is unfavourable to the 

 idea of the glacier having any great power of " churning up " the 

 deposit beneath. Here and there are large prominent protogine 

 blocks, several of which distinctly show by the striations on their 

 sides and surface, that the glacier has flowed over them. Three lie 

 near together ; their tops are polished and striated, and littered over 

 with moraine ; they do not form part of a lateral or ordinary ter- 

 minal moraine, but are in an open plain. Striations, sio8B and lee 

 seite — everything is just as it should be had the glacier flowed over 

 them, and each has a " tail " of moraine. The largest was about 

 12x7x5 yards. 



To return to the glacier itself. Where the ice rests on the level 

 stony plain, the subjacent materials, so far as I could make out, are 

 little if at all disturbed. This fully agrees with everything that I 

 have ever observed, viz. that when the glacier is passing over level 

 or slightly inclined materials, it does not much disturb them, but 

 thrusts up in front, when advancing, at most a mere scarf skin of turf 

 or debris. I questioned my guides, Franz Biirgener and Jean Martin, 

 both men of experience and more than ordinary intelligence. They 

 gave it as their belief, that when a glacier descends a slope of 

 moderate inclination, there is only bare rock beneath; when it passes 

 over a tolerably level surface, it overrides the debris in front, with- 

 out much disturbing it. 



The slope of rock, a considerable portion of which has now been 

 exposed by the shrinking of the glacier, lies at an angle of about 

 15^ or 20°. On ascending that on the left bank for some little dis- 

 tance, I found it possible to pass between the ice and the rock, and 

 availed myself of the opportunity, making sketches of the largest 



