35G 
ORIGIN OF RIVER BOTTOMS OR INTERVALES. 
page. Another still less obvious consequence of the with¬ 
drawal of the waters has occasionally been observed in these 
operations. The hydrostatic force with which the water, in 
virtue of its specific gravity, presses against the banks that 
confine it, has a tendency to sustain them whenever their com¬ 
position and texture are not such as to expose them to soften¬ 
ing and dissolution by the infiltration of the water. If then, 
the slope of the banks is considerable, or if the earth of which 
they are composed rests on a smooth and slippery stratum 
inclining toward the bed of the lake, they are liable to fall or 
slide forward when the mechanical support of the water is 
removed, and this sometimes happens on a considerable scale. 
A few years ago, the surface of the Lake of Lungern, in the 
Canton of Unterwalden, in Switzerland, was lowered by driv¬ 
ing a tunnel about a quarter of a mile long through the nar¬ 
row ridge, called the Kaiserstuhl, which forms a barrier at the 
north end of the basin. When the water was drawn off, the 
banks, which are steep, cracked and burst, several acres of 
ground slid down as low as the water receded, and even the 
whole village of Lungern was thought to be in no small danger. 
Other inconveniences of a very serious character have often 
resulted from the natural wearing down, or, much more fre¬ 
quently, the imprudent destruction, of the barriers which con¬ 
fine mountain lakes. In their natural condition, such basins 
serve both to receive and retain the rocks and other detritus 
brought down by the torrents which empty into them, and to 
check the impetus of the rushing waters by bringing them to 
a temporary pause; but if the outlets are lowered so as to 
drain the reservoirs, the torrents continue their rapid flow 
through the ancient bed of the basins, and carry down with 
them the sand and gravel with which they are charged, in¬ 
stead of depositing their burden as before in the still waters of 
the lakes. 
Mountain Lakes. 
It is a common opinion in America that the river mead¬ 
ows, bottoms, or intervales , as they are popularly called, are 
