GLACIER LAKES. 
403 
1714, the Kander, which drains several large Alpine valleys, 
ran, for a considerable distance, parallel with the Lake of 
Thun, and a few miles below the city of that name emptied 
into the river Aar. It frequently flooded the flats along the 
lower part of its course, and it was determined to divert it into 
the Lake of Thun. For this purpose, two parallel tunnels 
were cut through the intervening rock, and the river turned 
into them. The violence of the current burst up the roof of 
the tunnels, and, in a very short time, wore the new channel 
down not less than one hundred feet, and even deepened the 
former bed at least fifty feet, for a distance of two or three 
miles above the tunnel. The lake was two hundred feet deep 
at the point where the river was conducted into it, hut the 
gravel and sand carried down by the Kander has formed at its 
mouth a delta containing more than a hundred acres, which is 
still advancing at the rate of several yards a year. The Linth, 
which formerly sent its waters directly to the Lake of Zurich, 
and often produced very destructive inundations, was turned 
into the Wallensee about forty years ago, and in both these 
cases a great quantity of valuable land was rescued both from 
flood and from insalubrity. 
In Switzerland, the most terrible inundations often result 
from the damming up of deep valleys by ice slips or by the 
gradual advance of glaciers, and the accumulation of great 
masses of water above the obstructions. The ice is finally dis¬ 
solved by the heat of summer or the flow of warm waters, and 
when it bursts, the lake formed above is discharged almost in 
an instant, and all below is swept down to certain destruction. 
In 1595, about a hundred and fifty lives and a great amount 
of property were lost by the eruption of a lake formed by the 
descent of a glacier into the valley of the France, and a sim¬ 
ilar calamity laid waste a considerable extent of soil in the 
year 1818. On this latter occasion, the barrier of ice and 
snow was 3,000 feet long, 600 thick, and 400 high, and the 
lake which had formed above it contained not less than 
800,000,000 cubic feet. A tunnel was driven through the ice, 
and about 300,000,000 cubic feet of water safely drawn off by 
