374 Prof. BischofF on the Temperature of 



tain all the weight of the glaciers during their movement, it is 

 easy to conceive that the rocks upon which they repose must be 

 worn away by the friction, especially when the blocks are of a 

 harder material than the rock.* On that view the glacier can 

 be compared to a plane of a very extraordinary power. How 

 very cleavable some of the rocks in the Alps are, is exemplified 

 in the clay-slate of the Faulhorn and the ScJmarzhorn, which 

 colours the Bergelbach, on the upper Grindelwald g\aiQ\er^ black. 

 In the bed of the Schwarze Lntschi?ie I found large frasments 

 of this slate, which might be crumbled to pieces in the hand. 

 The separation of these blocks is certainly facilitated by their 

 being kept continually wet under the glacier. The glacier 

 streams carry these blocks away not only mechanically, but also 

 by dissolving them, when they consist of lime.f In proof of 

 this, Ebel^ points out the extraordinary winding furrows, which 

 are seen on the broad Mosa Alp, on the south side of the Mus- 

 chelhorn, on the northern side of the Gemmi, and on the small 

 plain of the Rhine glacier ; and which he is the more inclined to 

 take for the action of glacier streams, as the same furrows are 

 sometimes observed in the rocks on which the Rhine glacier rests 

 when in very hot summers any part of it is melted away. Be- 

 sides the detrition of the rocks on which the glacier rest, we have 

 also to take into consideration the deepening of the beds of gla- 

 cier torrents. In a quarry on the road in the valley of Frutigen 



the adventure related of him above, that the numerous blocks of stone which 

 he met with in his extraordinary journey under a part of the upper Grindel- 

 wald glacier, were tlie greatest impediments to his progress, because they al- 

 ways left him in doubt whether lie should crawl round them to the right or 

 to the left. 



• A wonderful example of the irresistible power of the glaciers when they 

 are in motion is related by Kuhn (Hopfner's Magazine, f. d. Naturkundo 

 Helvetiens 1787, i. 130.) 



t The considerable beds of calcareous sinter, which are found in the envi- 

 rons of Grindelwald, and on the way from thence to the Faulhorn, are proofs of 

 this. From the above mentioned observations of Stiihlin on the quantity of 

 water which is annually carried out of Switzerland by the Rhine, and from 

 Pagenstecher's analysis of the water of the Rhine, it may be calculated, sup- 

 posing the specific gravity of the fixed substances to be equal to that of car- 

 bonate of lime, that a cube of solid matter of 800 feet side is annually carried 

 out of Switzerland in solution alone. 



J Part II. p. 25C; III. 31 ; IV. HI. 



