596 
THE FRESH- WATER LOCHS OF SCOTLAND 
a mean depth of 151 feet, and the volume of water contained in it is 
estimated at about 22,^80 miUion cubic feet. 
The River Reuss joins the Aar not far from its junction with 
the Rhine, and drains the Lake of Lucerne. 
Lake of Lucerne (or Vierwaldstatter See, or Lac de Quatre 
Cantons) lies 1433 feet above sea-level, is 44 square miles in area, has 
a maximum depth of 702 feet, and a mean depth of 341 feet. It is 
estimated to contain 417,447 million cubic feet of water. From an 
ancient delta of the Muotta, and remains of terraces, it would appear, 
says Du Pasquier,^ that the water once stood nearly 100 feet above 
its present level. It would then have been continuous with the Lake 
of Zug. Heim regards the lake as a complication of several river 
valleys which were '* drowned at the same time. It belongs to 
what he terms " Rand-Seen," i.e. lakes situated on the north and 
south borders of the Alps, such as the Lake of Geneva, Ziirich, etc., 
caused by a subsidence of the Alps. The old river- terraces of the 
Reuss can still be traced in places along the valley near Zug, but 
they slope in the reverse way to the valley. From this and other 
evidence it is concluded that there has been a relative elevation of 
the land. The natural course of the river (which ran originally by 
Schwyz, through the Lake of Lowerz and the Lake of Zug, rejoining 
its present course by the valley of the Lorze) was thus changed, and 
it was turned west till it joined the Aa. The foldings in the neigh- 
bourhood of Lucerne changed the combined streams into a branching 
lake. The bays of Alpnach and Kussnach are a continuation of the 
valley of the Sarnen Aa, which forms the Lake of Sarnen. The 
peculiar shape of the Lake of Lucerne is thus accounted for : — The 
stretch from Ruochs to Brunnen is probably the old course of the 
Engelberger Aa, when it joined the ancient Reuss at Brunnen and 
continued with it by Schwyz and Zug ; the bottom of the Bay of Uri, 
where the Reuss enters the lake, is nearly flat, its two sides being 
reflections one of the other, and it appears to be a river-valley — a part 
of the course of the Reuss. Between Kindlimord and Schwybbogen 
a moraine crosses the lake, rising to within 164 feet of the surface.^ 
Lake of Zug has an area of about 15 square miles, a maximum 
depth of 649 feet, contains about 113,059 million cubic feet of water, 
and lies 1368 feet above sea-level. 
The River Linth, a tributary of the Aar, drains the Lake of 
Walen and the Lake of Zurich, and under the name of Li m mat flows 
into the Aar a little north of the junction with the Reuss. 
Lake of Walen is about 10 miles long, by 1| miles in maximum 
breadth ; the area is about 9 square miles, and the maximum 
1 Beitr. z. geol. K. d. Schw., xxxi., 1891. 
2 Heim, Beitr. z. geol. K. d. Schw., xxv., 1885. 
