714 PROF. GARWOOD ON THE ORIGIN OF SOME [Nov. 1902, 
VI. Genera Concnusions. 
The questions opened up by a discussion of the origin of the 
hanging valleys in the Alps are very wide, but I have confined my 
description to those types which have been attributed to direct 
excavation by ice; and, in the majority of cases cited, the whole 
question seems to turn on the relative power of excavation possessed 
by ice as contrasted with water. Having lived among glaciers most 
of my life, and for some years past having taken the greatest interest 
in all problems connected with ice, I must express my firm conviction 
that ice, far from hastening the erosion in a valley previously occu- 
pied by a river, appears to me in every case that can be tested to 
retard the erosion of its floor, and may therefore even be described 
as a protective agent. Here I am only repeating what has often 
been expressed before by those best acquainted with ice and snow. 
Mr. D. W. Freshfield, some years ago,’ in an admirable essay on the 
subject, which has been too often overlooked, summed up the question 
most tersely : 
‘T believe that a careful inspection of mountain-valleys shows conclusively 
the very limited extent of ice-action as a quarrier or excavator. And I would 
urge all who consider water, as compared with ice, ‘“‘the weaker agent,” 
to measure their respective performances at Grindelwald and Rosenlaui, where 
between the superficially ice-abraded rocks the torrent has carved for itself a 
bed hundreds of feet deep. . . . We find that where a barrier presents itself to 
a glacier furnished with a strong subglacial torrent, the tendency of the ice is 
to pass over the barrier, the tendency of the water to cut through it. The one 
acts as sandpaper, the other as a saw....So far as I can see, U-shaped 
valleys are not V-shaped—or trench-like—valleys broadened by ice, but 
V-shaped valleys are U-shaped valleys deepened by water-action.’ 
Here we have an exact description of what has really taken place 
in the Val Ticino. Prof. Heim, again, sums up in a similar manner 
when he remarks that ‘ glaciation is equivalent to relative cessation 
of valley-formation.’* It is to this cause that I would attribute 
the existence of the hanging valleys of the Ticino and Jongri type as 
described above, the lateral valleys being protected by glaciers, while 
the main valley was being deepened by water. 
If we examine the termination of glaciers at the present day, 
they are seen to rest invariably on a more or less raised platform, 
because of the protection which they afford to the ground under- 
neath. In the Arctic regions I have seen glaciers advancing over 
loose beach-material and picking it up in places, but doing no 
excavation; indeed, they are unable to push forward their ice- 
débris, and advance almost entirely by the shearing of the upper 
layers over those below. Take the case of the Upper Grindelwald 
Glacier, or any icefall, the glacier does not dig itself out a course: 
it simply falls over. The Rhone-Glacier icefield is, curiously 
enough, cited by Prof. Davis as a hanging valley due to excavation 
1 «Note on the Conservative Action of Glaciers’ Proc. Roy. Geogr. Soe, 
vol. x (1888) pp. 785, 787. 
2 «Handbuch der Gletscherkunde’ 1885, p. 897. See also T. G. Bonney, 
‘Do Glaciers Excavate ?’ Geogr. Journ. vol. i (1893) pp. 481-99. 
