The Idea of Glacial Erosion in America 
205 
were completely removed, and I came home with perhaps an 
over-ardent belief in the competence of glacial erosion, as is often 
the habit of the newly converted/’ 
Up to this time Davis had maintained a very conservative atti- 
tude when discussing glacial erosion; this conservatism appeared 
first in his ‘‘Basins of Glacial Erosion, and was explained in 
greater detail in later papers/^ 
1904 — G. K. GILBERT. 
Gilbert’s studies in Alaska, on which was based his discussion 
of Brigham’s paper at the Geological Society’s meeting in 1899, were 
not published till this date. The following extracts make clear 
Gilbert’s views on glacial erosion; his paper is one of the best con- 
tributions to the subject: 
^‘The hanging valley is especially significant in two lines of 
physiographic interpretation. It is a conspicuous earmark of 
the former presence of glaciers; and it helps to a conception of the 
magnitude of Pleistocene glacial erosion. 
‘^The value of an earmark depends on the principle of exclusion: 
glaciation is the only physiographic process known to produce 
such forms. 
After discussing other processes that may result in mild cases 
of discordance between the grades of major and tributary streams, 
Gilbert says: ‘‘But despite all qualifications the hanging valley 
is the most important witness yet discovered to the magnitude of 
the work accomplished by the alpine glaciers of the Pleistocene.”^® 
1905 — H. L. FAIRCHILD. . 
That there is not complete unanimity in the interpretations 
based on field evidence is shown by the following which refers 
more particularly to the Finger lake valleys of New York: 
Appalachia, vol. ix, p. 139. 
Proceedings of the Boston Society of N atural History, vol. xxi, January, ‘‘On 
the Classification of Lake Basins,” pp. 336-44, 1882. 
Ibid., vol. xxii. May, 1882, “Glacial Erosion,” pp. 19-58. U. S. Geological 
Survey, i8th Annual Report, part ii, “Glacial Modification of Form and Drainage,” 
pp. 179-B1, 1898. 
Harriman Alaska Expedition, “Alaska,” vol. iii, “Glaciers and Glaciation,” 
p. I15. 
^'Hhid.,^.ii6. 
Ibid., p. 1 18. 
