ce to glaciers. The facts on
which that opinion was founded are, I think, unassailable; but whether
the conclusion then announced fairly follows from the facts is, I
confess, an open question.

The arguments which have been thus far urged against the conclusion
are not convincing. Indeed, the idea of glacier erosion appears so
daring to some minds that its boldness alone is deemed its sufficient
refutation. It is, however, to be remembered that a precisely similar
position was taken up by many excellent workers when the question of
ancient glacier extension was first mooted. The idea was considered
too hardy to be entertained; and the evidences of glacial action were
sought to be explained by reference to almost any process rather than
the true one. Let those who so wisely took the side of 'boldness' in
that discussion beware lest they place themselves, with reference to
the question of glacier erosion, in the position formerly occupied by
their opponents.

Looking at the little glaciers of the present day--mere pigmies as
compared to the giants of the glacial epoch--we find that from every
one of them issues a river more or less voluminous, charged with the
matter which the ice has rubbed from the rocks. Where the rocks are
soft, the amount of this finely pulverised matter suspended in the
water is very great. The water, for example, of the river which flows
from Santa Catarina to Bormio is thick with it. The Rhine is charged
with this matter, and by it has so silted up the Lake of Constance as
to abolish it for a large fraction of its length. The Rhone is
charged with it, and tens of thousands of acres of cultivable land are
formed by the silt above the Lake of Geneva.

In the case of every glacier we have two agents at work--the ice
exerting a crushing force on every point of its bed which bears its
weight, and either rasping this point into powder or tearing it bodily
from the rock to which it belongs; while the water which everywhere
circulates upon the bed of the glacier continually washes the detritus
away and leaves the rock clean for further abrasion. Confining the
action of glaciers to the simple rubbing away of the rocks, and
allowing them sufficient time to act, it is not a matter of opinion,
but a physical certainty, that they will scoop out valleys. But the
glacier does more than abrade. Rocks are not homogeneous; they are
intersected by joints and places of weakness, which divide them into