1862.] EAJitSAY GLACIAL OEIGIN OP LAEE3. 197 



are necessarily sucli re-entering angles, from the common action of 

 running water; and, in Switzerland, ere these valleys were filled 

 with ice, they existed in some shape, and were drained by rivers that 

 deepened them and gave them a general form preparatory to the flow 

 of the ice that largely modified their outlines. I should no more 

 consider the re-entering angles a sign of gaping fracture in these 

 valleys than I would the bends of the Welsh valleys or of the tortuous 

 MoseUe. But even if at first sight one were inchned to believe the 

 space between the opposite cliifs between Brunnen and Fliihlen to be 

 an open fracture, if we take a moderate average slope for each side, 

 say of 65°, and produce it below the water, we get a depth, ere the 

 lines meet, of between 7000 and 8000 feet — a very improbable 

 depth for the original hollow of the lake. But it may be said that 

 the fracture has been much widened by degradation, the line of the 

 break merely giving a line of weakness, along which the surface- 

 drainage might widen the valley. If, however, we only take an angle 

 for the sides of the lake giving a moderate depth, the necessity for a 

 fracture does not exist, and we recur to some process of mere erosion 

 for the scooping of the hollow in which the water lies, that process 

 having, I consider, been the long-continued grinding of the ice of 

 the great glacier No, 3 of the Map. 



The Lake of Zurich. — The Lake of Zurich runs from N.W. to S.E., 

 across the average strike of the Miocene strata, which are much dis- 

 turbed towards its eastern end. It is bounded by high hills, much 

 scarred by the weather, on which the different Miocene strata often 

 stand out in successive horizontal steps. The Linth Canal and the 

 "WaUen See lie in an eastern prolongation of this valley, which is 

 still further extended to the valley of the Upper Ehine at Sargans. 

 The lake is about 25 English miles in length, by 2\ wide in its 

 broadest part. A great moraine partly dams it up at its outflow at 

 Zurich; and a second forms the shallow at Bapperswyl, where the lake 

 is crossed by a long wooden bridge. The general level of the water is 

 1341 feet above the sea, and only about 639 deep ; and the bottom of 

 the lake is therefore 702 feet above the sea. The limestone rocks at 

 Baden, on the Limat, are 1226 feet above the sea ; and the lake there- 

 fore lies in a true rock-basin, though it is probable that the old mo- 

 raine at Zurich accounts for the retention of the water of the lake at 

 its precise level. The long hoUow was in old times entirely filled by 

 the great glacier (No. 4 in the Map, PI. YIII.) which descended from 

 the mountains between the Todi and the Trinserhorn, through the 

 valley of the Linth, to Baden. 



The Wallen See. — The Wallen See lies in a deep valley, whose 

 cliffy slopes of Secondary rocks rise from 2000 to 3000 feet, and in 

 the Leistkamm 4500 feet above the surface of the lake. The lake itself 

 is 1391 feet above the sea ; and from the great steepness of its banks it 

 may be inferred that it is exceedingly deep, but none of the authorities 

 I have consulted give its soundings. A large branch from the great 

 Ehine glacier (No. 5 on the Map) joined that of the valley of Glarus 

 and Zurich through this wide gorge, and ground out the hoUow of 

 the WaUen See. 



