GLACIAL PERIOD. 
25 
ers, where they flow side by side, at the south¬ 
ern extremity of the lake, meeting, hut not 
mingling, the different color of their water 
marking the two parallel currents. In old 
times, when the glaciers filled all the valleys 
at the base of Mont Blanc, and to the east of 
it, uniting in the valley through which now 
runs the river Rhone, the glacier of the Arve 
came down to meet the ice from the valley of 
the Rhone, in the same manner as the river 
Arve now comes to meet the waters of the 
Rhone where they rush out from the southern 
end of the lake. 
This would be the proper place to consider 
the formation of the lakes of Switzerland, as 
well as their preservation by the agency of 
glaciers. But this subject is so intricate, and 
has already given rise to so many controversies 
Which could not be overlooked in this connec¬ 
tion, that I prefer to pass it over altogether in 
silence. Suffice it to say that not only are 
most of the lakes of Switzerland hemmed in 
by transverse moraines at their lower extrem¬ 
ity, but the lakes of Upper Italy, at the foot of 
the Alps, are barred in the same way, as are 
also the lakes of Norway and Sweden, and 
2 
