242 
terially to this knowledge, and have ex- 
tended the area of observation to the in- 
terior. Thus, even though there is yet 
much to learn, the knowledge that we now 
possess is sufficient to warrant a discussion 
of the general phenomena of Alaskan 
glaciation ; and since this is the object that 
has been most in my mind during the past 
six years, it has naturally appealed to. me 
ag the most fitting topic for the presidential 
address which I am called upon to give.?° 
THE EXISTING GLACIERS 
Condition of the Existing Glaciers 
Alaskan glaciation is, and has been, of 
the mountain type. That is to say, moun- 
tain snow fields have shed into mountain 
valleys, and through these the glacier ice 
has flowed to lower levels, in some cases 
even to the sea. Numerous glaciers, and 
in former times a still greater number, 
have flowed beyond their valleys and 
spread out fan-shaped at the mountain 
base, giving rise to the type of piedmont 
glacier which Russell has made known to 
us through his studies of the Malaspina 
glacier. 
The main region of existing glaciers oc- 
eupies a roughly semicircular area sweep- 
ing from the southern boundary of Alaska, 
northward, westward and southwestward, 
» The personal field work upon which this 
address is in part based was done in 1905 and 
1906 under the auspices of the U. 8S. Geological 
Society; and in 1909 and 1911 under the auspices 
of the Research Committee of the National Geo- 
graphie Society. To both of these bodies acknowl- 
edgments sre due for the generous financial sup- 
port given. The last two expeditions have been 
under the joint leadership of Professor Lawrence 
Martin and myself; and I wish especially to ac- 
knowledge my indebtedness to my colleague in two 
seasons of work, who was also an assistant on the 
first expedition. We have worked and observed 
together and have freely discussed all problems 
which have arisen. The results of our joint work 
are used in this address, as are also the results of 
other students of Alaskan glaciation. 
SCIENCE 
[N.S. Vou. XXXV. No. 894 
toward the Aleutian islands. From either 
end of this zone both the number and the 
size of the glaciers increase, and the eleva- 
tion of their termini decreases, attaining 
maximum development near the center of 
the semicircle that surrounds the head of 
the Gulf of Alaska. Altogether there are 
at least 47 tidal glaciers in this zone, the 
southeasternmost being the Le Conte 
Glacier, just north of Wrangell, and the 
westernmost McCarty Glacier on Kenai 
peninsula. Toward the ends of the glacier 
zone there are few and scattered instances 
of tidal glaciers; but in the central part of 
the zone they are numerous, and, where 
topographic conditions favor, are close to- 
gether. Thus in Glacier Bay there are at 
least twelve tidal glaciers; in Yakutat Bay 
three; and in Prince William Sound 
twenty. 
How many glaciers there are in this 
coastal area can not be even approximately 
estimated; but, counting large and small, 
tributaries and main ice streams, they are 
certainly to be numbered by the thousand. 
These vary in size from tiny ice masses in 
cirques, to valley glaciers two or three 
miles in breadth and thirty or forty miles 
in length; and up to the great Malaspina 
Glacier whose area is estimated to be 1,500 
square miles. From the Kenai peninsula 
to Cross Sound a very large proportion of 
the seaward face of the mountains is cov- 
ered with snow and ice, and glaciers exist 
in a majority of the valleys, deeply filling 
most of the larger ones. From Controller 
Bay to Cross Sound a succession of pied- 
mont glaciers and expanded bulbs of indi- 
vidual glaciers spread out between the 
mountain base and the sea. A journey 
along this coast is, therefore, a constant 
glacial panorama. 
Distribution of Eaisting Glaciers 
The mountains which fringe the Alaskan 
coast as a continuous barrier, as far west 
