CHARACTERISTICS AND DISTRIBUTION OF LAKES 597 
depth is 495 feet, the mean depth being 338 feet, and the cubic 
contents about 87,947 miUion cubic feet. It hes about 1378 feet 
above sea-level. The shores on the south side slope steeply, and on 
the north side are almost perpendicular, the cliffs rising to a height 
of nearly 3000 feet. 
Lake of Zurich lies 1341 feet above sea-level, and is about 
26 miles long, by 3 miles in greatest width, the area being 34 square 
miles. The maximum depth is 469 feet, the mean depth 135 feet, 
and the volume of water about 137,748 million cubic feet. It is said 
by some geologists to be a river-valley, the lower end of which has 
risen relatively and is dammed by a moraine. It was excavated by 
water in pre-glacial times, and subsequently occupied by the glacier, 
the lateral moraine of which forms the low range of hills to the 
west of the lake. Glacial deposits form the ridge which constitutes 
the lower lip of the lake, and the river has cut through the ridge to a 
depth of 36 feet, so that the lake must have formerly stood at that 
height above its present level, and must have been joined to the Lake 
of Walen, from which it is separated only by a flat plain. 
Lubbock ^ says that the valley of the Limmat was once occupied 
by the Rhine, and perhaps originally by the Sihl ; the Linth, or Upper 
Limmat, then flowed through what is known as the Glatthal, until 
the great Rhine glacier, pressing westwards, drove it into the valley 
occupied by the Sihl, and, subsequently retreating, left the Glatthal a 
deserted valley, now traversed only by the little stream of the Glatt. 
The valley of the Rhone, from the glacier where it takes its rise 
to the Lake of Geneva, forms the Canton of Valais, and that part of 
the valley lying between the gorge of St Maurice and Villeneuve was 
evidently at one time part of the Lake of Geneva, and would be so 
still if it were not for the deposits brought down by the Rhone. At 
and round Sierre are the remains of one of the most gigantic rock- 
falls in Switzerland, which must have dammed up the valley for a 
long time, but is now completely cut through both by the Rhone and 
by several tributary streams. The surface is very irregular, and has 
many small lakes in the depressions, the largest of which, a little 
north of Geronde, is about five-sixths of a mile long, by about a 
quarter of a mile broad. It lies 10 feet below the level of the Rhone, 
and has a depth of about 32 feet. 
Lake of Geneva (or Genfer See, or Lac Leman) is the largest 
lake in Switzerland, and acts as a filter and regulator of the 
river, which enters with remarkably turbid waters and leaves as a 
clear stream. In times of flood the level of the lake gradually rises, 
and the fluctuations of the lower course of the river are thus kept 
within moderate bounds by the regulating action of the lake. It is 
1 Op. cit, p. 391. 
