LAKES CONNECTED WITH GLACIAL ACTION. 187 
A still more striking illustration of the same absence of 
lakes where large glaciers abound is atforded by the Cauca¬ 
sus, a chain more than 300 miles long, and the loftiest peaks of 
vv^hich attain heights from 16,000 to 18,000 feet. This great¬ 
est altitude is reached by Elbruz, a mountain in lat. 43° N. 
three degrees south of Mont Blanc, but on the other hand 
3000 feet higher. The present Caucasian glaciers are equal 
or superior in dimensions to those of Switzerland, and like 
them give rise occasionally to temporary lakes by obstruct¬ 
ing the course of rivers, and causing great floods when the 
icy barriers give way. Mr. Freshfield, a careful observer, 
writing in 1869, says:* “A total absence of lakes on both 
sides of the chains is the most marked feature. Not only 
are there no great subalpine sheets of water, like Como or 
Geneva, but mountain tarns, such as the Dauben See on the 
Geinmi, or the Klonthal See near Glarus, are equally want¬ 
ing.” The same author states on the authority of the emi¬ 
nent Swiss geologist, Mons. E. Favre, who also explored the 
Caucasus in 1868, that moraines of great height and huge er¬ 
ratics of granite and other rocks “justify the assertion that 
the present glaciers of the Caucasus, like those of the Alps, 
are only the shadows of their former selves.” 
It seems safe to assume that the chain of lakes, of which 
the Albert Nyanza forms one in equatorial Africa, was due 
to causes other than glacial. Yet if we could imagine a 
glacial period to visit that region filling the lakes with ice 
and scoring the rocks w^hich form their sides and bottoms, 
we should be unable to decide how much the capacity of the 
basins had been enlarged and the surface modified by glacial 
erosion. The same may be true of the Lago Maggiore and 
Lake Superior, although the present basins of both of them 
afibrd abundant superficial markings due to ice-action. 
But to whatever combination of causes we attribute the 
great Alpine lakes one thing is clear, namely, that they are, 
geologically speaking, of modern origin. Every one must 
admit that the upper valley of the Rhone has been chiefly 
caused by fluviatile denudation, and it is obvious that the 
quantity of matter removed from that valley previous to the 
glacial period would have been amply sufficient to fill up 
with sediment the basin of the Lake of Geneva, supposing it 
to have been in existence, even if its capacity had been many 
times greater than it is now.f 
On the whole, it appears to me, in accordance with the 
views of Professor Ramsay, M. Mortillet, Mr. Geikie, and oth- 
* Travels in Central Caucasus, 1869, p. 452. 
t See Principles, vol. i., p. 420, 10th ed. 1867. 
