FEBRUARY 16, 1912] 
a glacier advances, the area of ice surface 
is increased, and its level rises, while with 
retreat the glacier surface is lowered and 
the area of ice is decreased; and if the 
terminus is in the sea there is a variation 
in the amount of floating ice with advance 
or recession. These changes produce a 
very pronounced effect on local climate, 
influencing both snowfall and ablation. 
Though the extent of the influence is nat- 
urally variable, it is roughly proportionate 
to the amount of the advance or retreat 
and to the area and height to which the 
variation extends. Other things being 
equal, the influence of an advance in en- 
couraging advance is greater and more 
prolonged when the ice ends on the land 
than when its terminus is in the sea; for 
on the land the ice spreads farther and 
remains in position longer. Thus the cli- 
matic influence of the last advance of Mala- 
spina Glacier is still dominant, while that 
of the neighboring Hubbard Glacier has 
been very greatly reduced by its notable 
recession. 
In illustration of these principles it may 
be stated that photographs of Hidden 
Glacier, which in the interval between 
1905 and 1909 had advanced two miles 
and had become greatly thickened, show 
a very notable difference in the amount of 
snow on and above the ice. This is un- 
doubtedly due to the double cause of 
greater snowfall and decreased melting, 
brought about by a modification of the lo- 
eal climate as a result of the advance. At 
Muir Glacier, which in the interval be- 
tween 1892 and 1911 has suffered such ex- 
cessive recession and lowering of its sur- 
face, the climatic difference is also dis- 
tinetly noticeable in photographs, .but with 
results of exactly the opposite kind. Here 
there is a smaller area of ice, the surface of 
that which remains is much lower than 
formerly, a larger proportion of the sur- 
SCIENCE 
205 
face is covered with moraine or discolored 
by débris, and the snow-covered area on 
the mountain slopes is greatly diminished. 
Without doubt the depth of annual snow- 
fall is markedly decreased, while the 
amount of ablation is notably increased in 
1911, as compared with 1892. Thus when 
a deficiency of snowfall, or other cause gives 
rise to a recession, the rate of ablation may 
come to be considerably in excess of the 
amount by which the ice supply is deficient, 
and the rate of retreat therefore may be- 
come much more rapid than would be ex- 
pected from the mere difference in ice 
supply. 
Recession Following Advance 
The problem of advance and recession is 
still further complicated by the apparent 
manner in which glacier advances take 
place. As shown by Finsterwalder and 
others,'® the Vernagt Glacier of the Tyrol 
responds to climatic variations by the pas- 
sage through the glacier of a wave which 
causes the terminus to move forward, the 
forward movement being concentrated in 
a brief period of time. Other glaciers, in 
the Himalayas, in Patagonia and in Spitz- 
te Winsterwalder, S., ‘‘Der Vernagtferner,’’ 
Wissenschaftliche Erganzungshefte zur Zeitschrift 
des D. u. O. Alpenvereins, 1. Band, 1. Heft, Graz, 
1897; Anbang, Blumeke, A., und Hess, H., ‘‘Die 
Nachmessungen am Vernagtferner’’; Blumcke, A., 
und Hess, H., ‘‘Beobachtungen an den Gletschern 
des Rofentales,’’ Mitt. des D. u. O. A.-V., Jahr- 
gang 1900, Nr. 4; ‘‘Einiges tiber den Vernagt- 
ferner,’’ ibid., Jahrgang 1902, No. 18; ‘‘Tief- 
bohrungen auf dem Hintereisferner,’’ 1902, dbid., 
Jahrgang 1902, Nr. 21; ‘‘Tiefbohrungen am 
Hintereisferner im Sommer 1908,’’ Zettschrift 
fiir Gletscherkunde, Band III., 1909, pp. 232-236; 
‘‘Tiefbohrungen am Hintereisgletscher,’’ 1909, 
ibid., Band IV., 1909, pp. 66-70; Hess, H., ‘‘ Zur 
Mechanik der Gletschervorstosse,’’ Petermanns 
Geogr. Mitt., 1902, Heft V.; Hess, H., ‘‘ Probleme 
der Gletscherkunde,’’ Zeitschrift frr Gletscher- 
kunde, Band I., 1906, pp. 241-254. 
