4354 MOUNTAIN LAKES. 
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. 
It is a common opinion in America that the river meadows, 
bottoms, or ¢atervales, as they are popularly called, are gene- 
rally the beds of ancient lakes which have burst their barriers 
and left running currents in their place. It was shown by Dr. 
Dwight, many years ago, that this is very far from being uni- 
versally true; but there is no doubt that mountain lakes were 
of much more frequent occurrence in primitive than in modern 
geography, and there are many chains of such still existing in 
regions where man has yet little disturbed the original fea- 
tures of the earth. In the long valleys of the Adirondack 
range in Northern New York, and in the mountainous parts of 
Maine, eight, ten, and even more lakes and lakelets are some- 
times found in succession, each emptying into the next lower 
pool, and so all at last into some considerable river. When 
the mountain slopes which supply these basins shall be strip- 
ped of their woods, the augmented swelling of the lakes will 
break down their barriers, their waters will run off, and the 
valleys will present successions of flats with rivers running 
through them, instead of chains of lakes connected by natural 
canals, 
A similar state of things seems to have existed in the ancient 
geography of France. “ Nature,” says Lavergne, “ has not ex- 
cayated on the flanks of our Alps reservoirs as magnificent as 
ducted into the canals of irrigation, becomes a source of great fertility.”—Za 
Propricta Fondiaria, ete., p. 144. 
The quantity of water escaping from the lakes by infiltration depends much 
on the hydrostatic pressure on the bottom and the walls of the lake-basins, and 
consequently the depression of the lake surface, diminishing this pressure, 
would diminish the infiltration. Hence it is possible that the lowering of 
the level of these lakes would manifest itself in a decreased supply of water 
for the springs, fontanili, and wells of Lombardy. 
