see, a limited value.

When the students of glacial action first began the great task of
interpreting these records, they were led to suppose that the amount
of rock cutting which was done by the ice was very great. Observing
what goes on, in the manner we have noted, beneath a valley glacier
such as those of Switzerland, they saw that the ice work went on
rapidly, and concluded that if the ice remained long at work in a
region it must do a vast deal of erosion. They were right in a part of
their premises, but, as we shall see, probably in another part wrong.
Looking carefully over the field where the ice has operated, we note
that, though at first sight the area appears to have lost all trace of
its preglacial river topography, this aspect is due mainly to the
irregular way in which the glacial waste is laid down. Close study
shows us that we may generally trace the old stream valleys down to
those which were no larger than brooks. It is true that these channels
are generally and in many places almost altogether filled in with
rubbish, but a close study of the question has convinced the writer,
and this against a previous view, that the amount of erosion in New
England and Canada, where the work was probably as great as anywhere,
has not on the average exceeded a hundred feet, and probably was much
less than that amount.

Even in the region north of Lake Ontario, over which the ice was deep
and remained for a long time, the amount of erosion is singularly
small. Thus north of Kingston the little valleys in the limestone
rocks which were cut by the preglacial streams, though somewhat
encumbered with drift, remain almost as distinct as they are on
similar strata in central Kentucky, well south of the field which the
ice occupied. In fact, the ice sheet appears to have done the greatest