l. The Italian Lakes are even more remarkable. The Lake of Como, 700
feet above the sea, is 1929 feet deep. Lago Maggiore, 685 feet above the
sea, is no less than 2625 feet deep.

If the mind is at first staggered at the magnitude of the scale, we must
remember that the ice which is supposed to have scooped out the valley
in which the Lake of Geneva now reposes, was once at least 4000 feet
thick; while the moraines were also of gigantic magnitude, that of
Ivrea, for instance, being no less than 1500 feet above the river, and
several miles long.

Indeed it is obvious that a glacier many hundred, or in some cases
several thousand, feet in thickness, must exercise great pressure on the
bed over which it travels. We see this from the striae and grooves on the
solid rocks, and the fine mud which is carried down by glacial streams.
The deposit of glacial rivers, the "loess" of the Rhine itself, is
mainly the result of this ice-waste, and that is why it is so fine, so
impalpable. That glaciers do deepen their beds seems therefore
unquestionable.

Moreover, though the depth of some of these lakes is great, the true
slope is very slight.

Tyndall and Ramsay do not deny that the original direction of valleys,
and consequently of lakes, is due to cosmical causes and geological
structure, while even those who have most strenuously opposed the theory
which attributes lakes to glacial erosion do not altogether deny the
action of glaciers. Favre himself admits that "it is impossible to deny
that valleys, after their formation, have been swept out and perhaps
enlarged by rivers and glaciers."

Even Ruskin admits "that a glacier may be considered as a vast
instrument of friction, a white sand-paper applied slowly but
irresistibly to all the roughness of the hill which it covers."

It is obvious that sand-paper applied "irresistibly" and long enough,
must gradually wear away and lower the surface. I cannot therefore
resist the conclusion that glaciers have taken an important part in the
formation of lakes.

The question has sometimes been discussed as if the point at issue were
whether rivers or glaciers were the most effective as excavators. But
this is not so. Those who believe that lakes are in many cases due to
glaciers might yet admit that rivers have greater power of erosion.
There is, however, an essential difference in the mode of action. Rivers
tend to regularise their beds; they drain, rather than form lakes. Their
ten