FEBRUARY 16, 1912] 
broad expanses of snow and ice which 
serve to retard summer melting. 
In the distribution of its glaciers 
Alaska presents a striking contrast to that 
part of Europe in the same latitude. 
There are no glaciers in southern Scandi- 
navia, in the latitude where, in Alaska, the 
glaciers are largest; and while in Norway 
there is an increase in glaciation north- 
ward, in Alaska there is a decrease. In 
Norway the influence of latitude is per- 
mitted to exert its normal effect; but in 
Alaska the influence of latitude is effectu- 
ally counterbalanced by variations in 
topography and in the vapor content of 
the air. This contrast may have some 
significance in the explanation of the de- 
velopment of extensive ice sheets in north- 
western Europe and northeastern America, 
while northern Asia and northwestern 
North America, in the same latitude, were 
free from continental glaciation. 
Tce Flooded Valleys and Through Glacier 
Systems 
Only by individual description of a 
large series of instances would it be pos- 
sible to adequately portray the varied 
characteristics of the Alaskan glaciers. As 
in the Alps, Caucasus and Himalayas, the 
valley glacier is the normal type, but with 
many variations in form, size and rate of 
motion. From the lofty peaks a series of 
radiating glaciers usually spread outward; 
but throughout much of the mountain 
area there is a complex of ramifying 
elacier systems. Nowhere, so far as known, 
is there a development of the ice cap condi- 
tion such as is found in Norway, Spitz- 
bergen and Iceland, for the mountains are 
so lofty and rugged that the valley slopes 
serve to drain away the surplus snow that 
falls upon the steep mountainsides. 
Still the snowfall is so heavy, especially 
near the coast, that, in the process of 
SCIENCE 
245 
drainage, the valley systems are deeply 
filled with ice in spite of the ruggedness 
and high elevation. In the area of great- 
est glacier development, in the St. Elias 
region, the extent of snow and ice is so 
great as to have led Russell to speak of it 
as ‘‘a vast snow-covered region, limitless 
in expanse, through which hundreds and 
perhaps thousands of barren, angular 
mountain peaks projected,’’ and to com- 
pare it to the “‘borders of the great Green- 
land ice sheet.’? How deeply these vast 
glacier systems fill the valleys we have no 
means of telling; nor can we even estimate 
the aggregate length or area of the maze 
of ice streams that flood the mountain val- 
leys. In a region where dozens of glaciers 
are known to have lengths of from twenty- 
five to forty miles, it can not be doubted 
hat the aggregate length of the ice streams 
is thousands of miles, and that the total 
area of snow and ice amounts to tens of 
thousands of square miles. 
Although the vast bulk of ice that is 
slowly draining away the snow that falls 
among the Alaskan mountains maintains 
the valley glacier condition rather than 
developing an ice cap, it gives rise to an 
intermediate condition, as Russell’s de- 
scription intimates. That is, although the 
mountain summits are not flooded, the val- 
leys are. For example, one may start from 
Yakutat Bay and, traveling up one of the 
large glaciers, rise above the snowline by 
a moderate grade and finally reach a flat, 
snow-covered divide, beyond which, also 
with moderate grade, a descent leads down 
a glacier flowing in the opposite direction. 
Or, to the right or the left, also over flat, 
snow-covered divides, an easy route is open 
down other glaciers. In this way one may 
travel for scores of miles, going from one 
valley to another and from one glacier to 
another, but crossing only broad, flat snow 
divides. So deeply is the region submerged 
