208 ANNALS NEW YORK ACADEMY OF SCIENCES 



is to be seen. All these topographical features are characteristic of an 

 area in which alpine glaciation has been active. 



The valley of the East Fork of Foss Eiver may serve as an example of 

 a glaciated valley (Fig. 4) ; one is particularly impressed with the steep- 

 ness of the valley walls. In one place the valley wall rises 3000 feet in a 

 horizontal distance of 3500 feet. The valley floor is half a mile wide and 

 beyond this the opposite wall rises steeply again. Another excellent 

 trough valley is the one occupied by Deception Creek. Trough lakes are 

 numerous. The largest of the lakes of the Skykomish Basin, Lake 

 Dorothy, is probably the best example. It lies in a hanging trough valley 

 whose sides rise precipitately about 1500 feet on either shore of the lake. 

 Passage along the lake shore is hazardous or impossible because of this 

 steepness. The lake is deep and pours its waters over a solid granodiorite 

 barrier through a narrow gorge which has apparently been cut since 

 glacial retreat. 



There are innumerable examples of cirques, such as those occupied by 

 Malachite 'Lake and by Crystal Lake. The walls of these cirques rise 

 precipitously for 1000 feet, and the sight of a score of cascades tumbling 

 into the horseshoe-shaped basins with a mingled roar and hiss as they 

 fall into the j^ools which their energy has hewn is one that once seen is 

 forever retained as one of the magnificent memories of mountaineering. 

 These cirques are more often than otherwise occupied by tarns, or shal- 

 low, circular bodies of water, scores of which are mapped, besides other 

 scores which escaped the cartographer's attention. 



Hanging valleys are frequent, but perhaps the finest and most pictur- 

 esque example is the one occupied by Lake Katharine ( Fig. 5 ) . It hangs 

 1200 feet above the West Fork of Foss Eiver. The valley is exceedingly 

 steep-walled, and the vista opened before one standing on a commanding 

 height at the lower end displays the whole length of the box-like valley 

 with its extraordinarily lovely sheet of water, reflecting the snowy moun- 

 tains at its head. Turning down stream one can see a narrow spillway 

 along which the foaming water plunges to a second lake several hundred 

 feet below, and beyond this a similar chute that gives outlet to Foss 

 River more than 1000 feet below. 



Serrate ridges and alpine peaks will be considered later'. Possibly the 

 best occurrence is the southeast trending ridge that forms the apex of 

 the angle between the Skykomish and Beckler Rivers. Truncated spurs 

 are well shown at S in the block diagram (Fig. 6). 



Till-covered valley walls occur along the Skykomish, Beckler, Tye and 

 Snoqualmie Rivers. Near the confluence of Martin Creek and the Tye 

 River, this boulder clay extends 250 feet above the stream level. Its 



