378 



GLACIER LAKE -THE MARJELEN SEE. 



[Ch. XVI. 



the lake is full, has an angle of 29°. The vertical height of 

 the upper part of the shelf a, above the lowest subaqueous 

 portion c, is thirty-six feet. The fundamental rock consists of 

 highly inclined mica-schist. The materials of the terrace or 

 shelf are such as might have been derived chiefly from the 



waste of the steeply-sloping flanks of the boundary heights/ 



a 



j 



Aletsch 



Glacier 



Fig. 24. 







! he 



Marjelen See 



a 



/*' **•* - - - . - , * . r* — -— . mmmmm 



Valleyof-Yiesck 



Mica \ Schist 



Relative position of the lake called Marjelen See and the Valley of Viesch. 



a b. Col or dividing ridge between the two valleys. 

 c. Vertical cliff of ice forming the dam. 



but they consist, no doubt, in part of fragments of rock, 

 stranded by miniature icebergs, such as e, (fig. 23) of which 

 many are continually detached from the barrier of ice at the 

 lower end of the lake. I saw many of these bergs floating 

 on the lake, with stones and mud frozen into them, parts of 

 the moraine of the Aletsch Glacier, and which may have 

 come from distant mountains. The icy fragments were melt- 

 ing, and as their centres of gravity changed, they frequently 

 capsized. The materials thus transported must be strewed 

 in part over the whole bottom of the lake, but by far the 

 greater number must be stranded on the shore when the lake 

 is full, or in its normal condition. In fig. 24, the position of 

 the lake dammed up by the Aletsch Glacier, and its relation to 

 the adjoining valley of Viesch, is shown. The col or lowest 

 depression between the two valleys is seen at a b, and along 

 this level the stream issuing from the Marjelen See, at a, flows 

 habitually to 6, where it falls in a cascade over the rocks, on 

 its way to the valley of Viesch. In passing from a to b, it 

 cuts through ancient moraine matter, and its channel has 



