1873.] B0NXEY ALPINE LAKES. 383 



I must as briefly as possible sketch out the principal physical 

 features of each one, and in drawing conclusions from these shall 

 lay especial stress upon the two following propositions : — 



(1) That, supposing a glacier able to excavate a lake-basin, there 

 must exist above the head of each lake a district capable of 

 producing a considerable glacier. 



(2) That under no circumstances can glaciers, especially near 

 their heads, erode considerable precipices or slopes approximately 

 vertical. 



The former of these propositions, which amounts to saying that 

 the lake-basins must lie in the lines of what may have formerly 

 been considerable ice-streams (as, for example, do those of Geneva, 

 Como, Maggiore), appears to me as self-evident as saying that a 

 large river cannot exist without a large catchment-basin. The 

 latter will, I think, appear almost as self-evident when the slight 

 flexibility of the ice-stream is considered. The glacier planes, though 

 with varying force ; it cannot dig. 



Best known, and in many respects most remarkable, among these 

 lakes of the North-eastern Alps is the Konigsee. It is 1996 feet 

 above the sea, about 2 miles long, and varies in breadth from f mile 

 at its upper and lower end to 1| mile in the middle. The depth is 

 769 feet*. It occupies a deep valley, almost a gorge, surrounded 

 by a loop-shaped wall of mountains, whose broad undulating top is 

 about 7000 feet above the sea, and is capped by peaks which rise 

 about 1000 feet higher, no one of them surpassing 9000 feetf. 

 The most marked characteristic of this lake is the extreme steepness 

 of its banks, which rise precipitously from the margin, generally for 

 at least 2000 feet — so precipitously, indeed, that the few narrow 

 tracks which, lead from the upper pastures to the water's edge would 

 remind the traveller, were it not for the abundance of trees, more of 

 the southern face of the Gemmi than of any other path in the Alps. 



A low bank of debris, about half a mile across, divides the upper 

 end of the Konigsee from the Obersee, which is about 1| mile long 

 and wide, and 155 feet deep. A glance at this from the slopes 

 above the Konigsee at once shows its true character. The steep 

 sides of the valley in which the latter lake lies sweep on without 

 interruption from its present head, becoming more and more pre- 

 cipitous, till the glen is terminated by a magnificent wall of cliffs, 

 rising as nearly as possible vertically for at least 1000 feet. It is, 

 in fact, a cirque, similar to those which I have described in a former 

 communication %. One cascade, of some size, resembling the Staub- 

 bach, falls down this gigantic wall, which is streaked again and 

 again by smaller streamlets, generally dry in summer. The barrier 

 between the Obersee and Konigsee is formed by two great taluses of 

 debris, which have descended from glens that open on opposite sides 

 of the valley ; and beneath the cliffs at the head of the former lake 



* These measurements are given on the authority of Dr. H. Wallmann. " Die 

 Seen in der Alpen" (Jabrbuch des osterreichischen Alpen-Vereines, Band iv. p. 1). 

 f The Watzmann, the highest of the group, is 8988 feet. 

 \ Quart. Journ. Geol. Soc. vol. xxvii. p. 312. 



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