No. 14. — Glacial Erosion in .France, Switzerland and Norway. 
By William Morris Davis. 
Introductory . — Eighteen years ago I presented to this Society 
an essay on Glacial Erosion, in which my own observations were 
supplemented by a review of all that I could find written on the 
subject, in the hope of reaching some safe conclusion regarding 
what was then (as it is still) a mooted question. Although recog¬ 
nizing effective erosion to depths of “a moderate number of feet” 
where ice pressure was great and motion was rapid, in contrast to 
deposition where pressure and motion were reduced and where the 
amount of subglacial drift was excessive, I could not at that time 
find evidence to warrant the acceptance of great glacial erosion, 
such as was advocated by those who ascribed Alpine lakes and 
Norwegian fiords to this agency. In a retrospect from the present 
time, it seems as if one of the causes that led to my conservative 
position were the extreme exaggeration of some glacialists, who 
found in glacial erosion a destructive agency competent to accom¬ 
plish any desired amount of denudation — an opinion from which 
I recoiled too far. Since the publication of my previous essay I 
had gradually come to accept a greater and greater amount of 
glacial erosion in the regions of active ice motion ; but in spite of 
this slow change of opinion, the maximum measure of destructive 
work that, up to last year, seemed to me attributable to glaciers 
was moderate; and it was therefore with great surprise that I then 
came upon certain facts in the Alps and in Norway which demanded 
wholesale glacial erosion for their explanation. The desire of some 
years past to revise and extend my former essay then came to be a 
duty, which it is the object of this paper to fulfil. 
My former revision of the problem divided the arguments for 
glacial erosion under four headings: observations on existing 
O O o 
glaciers and inferences from these observations; the amount and 
arrangement of glacial drift; the topography of glaciated regions; 
and the so-called argument from necessity, — that is, the belief 
that glaciers must have done this and that because nothing else 
