Of the two glaciers just mentioned the Klickitat is the larger and more typical. The Rusk, however, is of interest because it flows, greatly crevassed, down a narrow flume or couloir on the east slope. Its bed, Reid suggests, may have been the channel of "a former lava flow, which, hardening on the surface, allowed the liquid lava inside to flow out; and later the top broke in." The Klickitat glacier lies in a much larger canyon, which it has evidently cut for itself. This is one of the most characteristic glacial amphitheaters in America, resembling, though on a smaller scale, the vast Carbon glacier _cirque_ which is the crowning glory of the Rainier National Park. The Klickitat basin is a mile wide. Into it two steep ice-streams cascade from the summit, and avalanches fall from a cliff which rises two thousand feet between them. (See pp. 98 and 99.) [Illustration: North Peak of Mount Adams, with The Mountaineers beginning their ascent, in 1911. Their route led up the ridge seen here, which divides Lava glacier, on the left, from Adams glacier, on extreme right.] The glacier is more than two miles long. It ends at an elevation of less than six thousand feet, covered with debris from a large medial moraine formed by the junction of the two tributary glaciers. Like the other Mount Adams glaciers, and indeed nearly all glaciers in the northern hemisphere, it is shrinking, and has built several moraines on each side. These extend half a mile below its present snout, and the inner moraines are underlaid with ice, showing the retreat has been recent. South of the Klickitat glacier, a part of the original surface of the peak remains in the great Ridge of Wonders. Rising a thousand feet above the floor of Hellroaring Canyon, which was formerly occupied by Mazama glacier, now withdrawn to the slope above, this is the finest observation point on the mountain. "The wonderful views of the eastern precipices and glaciers," says Reid, "the numerous dikes, the well preserved parasitic cone of Little Mount Adams, and the curious forms of volcanic bombs scattered over its surface entirely justify the name Mr. Rusk has given to this ridge." [Illustration: Snow Bridge over Killing Creek, north of Mount Adams.] Adams glacier, upon the northwest slope, with a length of three miles, is the largest on the mountain. This and the two beautiful ice streams on the northeast, named after Prof. W. D. Lyman, are notable for their ice-falls, half-mile drops of tumbling, frozen rivers.