Researches on Existing Glaciers. 255 



than the most beautiful theory could be. There is now no one 

 who ventures to dispute the importance of a phenomenon so 

 generally distributed; but some geologists, refusing to adopt the 

 glacial theory, have pretended that the polished surfaces, on 

 which glaciers of the present day repose, are not the result of 

 the action of glaciers, but have been produced by a cause an- 

 terior to their existence. This opinion has nothing probable 

 in it, because, in the Alps, the phenomenon is too intimately 

 connected with glaciers to be regarded as independent of 

 them ; but it would be of importance to have an experimental 

 proof of this. As all the glaciers of the Bernese Oberland 

 are at present in a state of increase, I conceived the idea of 

 making an accurately determined mark at a place which I 

 supposed would soon be invaded by the ice. For this purpose, 

 I caused a corner of the glacier to be removed ; and it was by 

 this means that I assured myself that the intermediate bed of 

 mud and of gravel was so frozen as to be incorporated with 

 the rock. We succeeded, however, in uncovering the surface 

 of the rock ; and we then cut out in the polished rock, at a 

 place whose position was accurately ascertained by means of 

 fixed points, a triangle, having a base of about a foot, from 

 which we removed the rock to the depth of half an inch, hav- 

 ing rendered the surface as rough as possible. If, as I have 

 no doubt, it be really the glacier which polishes the rock, this 

 triangle ought to be repolished and striated within a cer- 

 tain number of years. We have no idea of the time re- 

 quired by a glacier to polish its bed, but it is probable that the 

 duration of that time varies according to the weight of the 

 masses, and according to the nature of the rock ; and, as the 

 bed of the glacier of Rosenlaui consists of a black limestone 

 sufficiently susceptible of being acted on, we may hope to ob- 

 tain a result more speedily than if the rock had been gneiss or 

 granite. 



I had hoped that the glacier would soon have invaded anew 

 the place we had uncovered in the mouth of March ; but I 

 was a little disappointed when I visited our glacier with 

 Messrs Forbes and Heath in the month of August following, 

 to see my triangle still exposed. The glacier had advanced, 

 it is true, but on its left side, while the right flank had re- 



