About Mount Cook, and in the elevated plateau east of Yakutat bay, there has been deeper erosion than about Mount St. Elias. The glaciers in this region occupy deep valleys radiating from the higher peaks; but whether these are really valleys of erosion is not definitely known. In some instances, changes of dip on opposite sides of the valleys indicate that they may in part be due to faulting; but, owing principally to the fact that every basin has its glacier, it has not been practicable, up to the present time, to determine how they were formed. The crests of the mountains are always sharp and angular, by reason of the rapid weathering of their exposed summits, but while disintegration is rapid, no evidences of pronounced decay are noticeable. The peaks on the summits of the St. Elias range are either pyramids or roof-like crests with triangular gables. These forms have resulted from the weathering of schist in which the planes of bedding are crossed by lines of jointing. {176} PART IV. GLACIERS OF THE ST. ELIAS REGION. NATURAL DIVISIONS OF GLACIERS. The glaciers of the St. Elias region form two groups. The ice-streams from the mountain are of the type found in Switzerland, and hence termed _Alpine glaciers_. The great plateau of ice along the ocean formed by the union and expansion of Alpine glaciers from the mountains belongs to a class not previously described, but which in this paper have been called _Piedmont glaciers_. The representative of the latter type between Yakutat bay and Icy bay is the Malaspina glacier. Both types are to be distinguished from _Continental glaciers_. ALPINE GLACIERS. The glaciers in the mountains are all of one type, but present great diversity in their secondary features, and might be separated into three or four subordinate divisions. The great trunk glaciers have many tributaries, and drain the snows from the mountains through broad channels, which are of low grade throughout all the lower portions of their courses. Besides the trunk glaciers and the secondary glaciers which flow into them, there are many smaller glaciers which do not join the main streams, but terminate in the gorges or on the exposed mountain sides in which they originate. These have nearly all the features of the larger streams, but are not of sufficient volume to become rivers of ice. A minor division of Alpine glaciers for which it is convenient to have a special name includes those that end in the sea and, breaking off, form icebergs. These may be designated as "tide-water glaciers." Typical examples of this class are furnished by the Dalton and Hubbard glaciers, but other ice-streams having the same characteristics occur in Glacier bay, in Taku inlet, and at the heads of several of the deep fjords along the coast of southeastern Alaska.