ALASKA. 37 
length of from 60 to 300 miles or more, flow through a region pre- 
senting great variety of topographic forms, and transport abundant 
sediment to be deposited in the extensive deltas at their mouths. 
Their characteristics are impressed upon them by the region traversed, 
and the glacial slopes of the lofty Pacific ranges have imparted to 
them a resistless energy which makes their availability to the ordinary 
uses of civilization very difficult. 
The rivers of the western coast are of an entirely different character. 
These broad, gently flowing streams derive their waters from the 
remotest sources in the interior, and most of them offer easy ways of 
transportation and communication for hundreds of miles inland. The 
most important are (from south to north) the Kuskokwim, Yukon, 
Selawik, Kowak (or Kobuk), and Noatak. 
Most of the drainage from the western side of the Alaskan Range 
finds its way to the Kuskokwim, and the same river drains the little- 
explored area westward toward the coast. Its tributaries follow 
widely divergent courses; the upper ones interlock with those of the 
Yukon, the divide between the two systems being low. After gather- 
ing many important tributaries from various sources, the main stream 
flows southwestward through a region of hills and lowlands to Bering- 
Sea. 
The Yukon River and its tributaries form a drainage system com- 
parable to that of the Mississippi. From the source of its longest 
tributary, far within Canadian territory, to its mouth in Bering Sea 
the distance is over 2,000 miles. Where it enters Alaska, a few miles 
above Eagle, it has already become a river of great size, and for 1,300 
miles thereafter it traverses the plateau region and gathers to itself 
the waters of many tributaries. Its course within Alaska shows a 
close adjustment to the main structural lines, which have already been 
considered. 
A study of the entire Yukon drainage would require familiarity 
with a large part of Yukon Territory and British Columbia. It is 
sufficient here to realize the fact that this great system has tribu- 
taries ramifying far within the Rocky Mountains to the east and in 
close proximit}^ to the Arctic and Pacific oceans on the north and 
south, and that in gaining control of this vast area the whole sys- 
tem has entrenched itself to a depth of 1,000 to 3,000 feet in the plateau, 
so that the smaller streams, the tributaries of the larger ones, and the 
main streams themselves often flow in narrow, steep-walled canyons 
below the general surface, while in other portions of their courses they 
traverse lowlands of great extent. 
From the Canadian boundary, where it is only half a mile to a mile 
in width, as far as Circle the valley of the Yukon is comparatively 
narrow and is bounded by the Yukon Plateau. From Circle to within 
a short distance of Rampart the river traverses a great lowland, known 
