172 
SCENERY OF SWITZERLAND. 
40 metres without reaching the bottom of the valley, 
and they are estimated at a thickness of over 
100 metres.* 
Indeed, unless there is some cross ridge of which 
we have no evidence, it follows that, as the lake has 
a depth of 142 metres, we may, even without allow- 
ing for any slope of the valley, assume that the dam 
of glacial matter must have as great a height, or, 
adding the 1 1 metres, no less than 675 feet. 
I have throughout spoken of this valley as that 
of the Limmat. As a matter of fact, however, it 
was at one time occupied by the Rhine, and per- 
haps originally belonged to the Sihl; the Linth or 
Upper Limmat then flowed through what is now 
known as the Glatthal, until the great Rhine glacier, 
pressing westwards, drove it unto the then valley 
of the Sihl, and subsequently retreating left the 
Glatthal a deserted valley, only traversed by the little 
stream of the Glatt. 
The Sihl. 
With the history of the Lake of Zurich, that of 
the river Sihl is closely connected. Its course is 
curious, and its history veiy interesting. 
Rising in the mountains of Schwyz it makes 
* Pu Pasquier, Beitr. ?. G(ol, K, d. Schw., P. xxici. 
