MOUNTAIN LAKES. 421 



long valleys of tlie Adirondack range in Northern New York, 

 and in the mountainous parts of Maine, eiglit, ten and even more 

 lakes and lakelets are sometimes found in succession, each empty- 

 ing into the next lower pool, and so all at last into some consid- 

 erable river. When the mountain slopes which supply these 

 basins shall be stripped of their woods, the augmented swelling 

 of the lakes will break down their barriers, then* 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 exca- 

 vated on the flanks of our Alps reservoirs as magnificent as those 

 of Lombardy ; she had, however, constructed smaller but more 

 numerous lakes, which the improvidence of man has permitted 

 to disappear. Auguste de Gasparin demonstrated more than 

 thirty years ago that many natural dikes formerly existed in the 

 mountain valleys, which have been swept away by the waters," * 



Many Alpine valleys in Switzerland and Italy present unques- 

 tionable evidence of the former existence of chains of lakes in 

 their basins, and this may be regarded as a general fact in regard 

 to the primitive topography of mountainous regions. Where the 

 forests have not been destroyed, the lakes remain as character- 

 istic features of the geographical surface. But when the woods 

 are felled, these reservoirs are sooner or later filled up by wash 

 from the shores, and of course disappear. Geologists have calcu- 

 lated the period when the bottom of the Lake of Geneva will be 

 levelled up and its outlet worn down.f The Rhone will then 

 flow, in an unbroken current, from its source in the great Rhone 

 glacier to the Mediterranean Sea. 



* ^conomie SurcUe de la France, p. 289. 



f Railway cuttings tlirough the ancient deposits of the upper Rhone, at its 

 entrance into the Lake of Geneva, have furnished data for important histor- 

 ical and chronological computations as to the geological agency of this river ; 

 and the later deposits of the same locality are very instructive in regard to the 

 action of aquatic and semi-aquatic vegetation in solidifying those deposits and 

 converting them into dry land. 



