244 
extensively developed along the seaward 
face of the coastal ranges is plainly due to 
the fact that the prevailing winds are 
from the ocean, and that in blowing over 
the warmed waters of the Gulf of Alaska 
a large amount of vapor is moved forward 
and precipitated in the form of snow upon 
the lofty mountain barrier. It is where 
the coastal barrier is most complete and 
highest that the snowfall is heaviest and 
the development of glaciers greatest. The 
annual precipitation varies greatly, records 
of from 100 to 190 inches having been 
obtained at stations along this coast; 
but there is no knowledge as to the pre- 
cipitation among the lofty mountains, ex- 
eepting the knowledge that it is very 
heavy and mainly in the form of snow. 
In a region where from 10 to 40 feet of 
snow falls each year at sea level, there 
must be exceedingly heavy snowfall at ele- 
vations where the precipitation is all in the 
form of snow. As an indication of the vast 
snowfall among the mountains, reference 
may be made to Schrader’s observation of 
from 8 to 12 feet of snowfall on Valdez 
Glacier during a week late in: April and 
early in May, 1898. By such heavy pre- 
cipitation the snowline is depressed to lev- 
els of 2,500 to 3,500 feet on the seaward 
face of the mountains, and to even lower 
levels back in the mountains where the 
local climate is cooled by the chill of the 
surrounding areas of snow and ice. 
Sinee the damp winds precipitate so 
much vapor in crossing the mountain bar- 
rier, there is a deficiency for precipitation 
on the inner slopes of the mountains and on 
the ranges further inland. Moreover, such 
winds as sweep into interior Alaska from 
either the Arctic Ocean or Bering Sea bear 
but a limited vapor burden, since the water 
of these seas is cold in summer and more 
or less completely ice-covered in winter. 
Records at Eagle give a rainfall of only 
SCIENCE 
(N.S. Vou. XXXV. No. 894 
11.35 inches; but the precipitation is 
doubtless higher toward the west and in 
the lofty mountains. 
The winters of the interior are prevail- 
ingly clear and cold with moderate snow- 
fall—for example, only 2 or 3 feet of snow 
falls in the Copper River Basin; but in 
spring and summer the temperature is so 
high that the snow quickly melts even well 
up on the mountain slopes. Thus, even in 
the neighborhood of the Arctic Circle a 
plateau from 3,000 to 6,000 feet in eleva- 
tion is completely free from snow in sum- 
mer, as is also a large portion of the Endi- 
cott mountains; and, whereas the snowline 
on the seaward face of the St. Elias range 
is about 3,000 feet, it is more than twice as 
high as that in the interior three or four 
hundred miles further north. The exact 
elevation of the snowline in the interior 
can not be stated, and indeed it must vary 
greatly from place to place. In general, 
however, it is above 6,000 feet.1? 
This rise in the snowline toward the 
north is interesting as showing how impor- 
tant the element of precipitation is. The 
snowline is lower and the glaciers are 
larger where the mean annual temperature 
is high and the precipitation is heavy, than 
in the much colder climate further north 
where, however, precipitation is light and 
the short summers are warm. A similar 
variation is noticed in the coastal moun- 
tains where the snowline is considerably 
higher along the inner fiords than on the 
outer coast where the precipitation is 
heavier. It is to be noted, however, that 
in the latter place not only is there a 
greater depth of snow to be melted, but in 
the neighboring lofty mountains there are 
® Oscar Rohn (Twenty-first Annual Report U. 8. 
Geological Survey, pt. 2, 1899-1900, p. 413) states 
that on September 1 the snowline was 7,500 feet 
in one part of the Wrangell Mountains, and was 
then descending. 
