MARGINAL GLACIAL DRAINAGE FEATURES 539 



Johnson Hollow channel. — Two and one-half miles north of the 

 town of Millport, and an equal distance east-southeast of Moreland 

 is the beginning of another interesting lateral channel. It was formed 

 by a stream from a small lateral lobe which pushed from the great 

 Seneca valley ice-tongue for a short distance through the gap 

 in the hihs on the west side of the valley. The stream flowed 

 for a little over a mile in a northeasterly direction, almost opposite 

 to that of the ice-motion in the adjacent valley. It then turned and 

 flowed a little south of west for another mile, then southward through 

 Johnson Hollow and finally back to the ice three miles below the start- 

 ing point. (See Fig. 9.) 



This channel, Hke those already described, has a flat, swampy 

 bottom and distinctly trimmed banks. For the first mile of its 

 course its width varies from 100 to 150 feet. The elevation at the 

 beginning is 1,200 feet, and at the foot of Johnson Hollow, where it 

 again reached the ice tongue, 1,000 feet. This gives a drop of two 

 hundred feet in a distance of three miles, or an ice-slope of sixty- 

 six feet per mile. 



At the head of Johnson Hollow is a series of several channels of 

 which this is one. The entire series will be fully described on a later 

 page with special reference to the relation of the various channels to 

 each other and to the ice-front. 



Watkins Hill channel. — Beginning on the west side of Watkins 

 Hill (Fig. 2, Watkins Sheet, U. S. G. S.) is another lateral channel 

 which after a course of about two and one-fourth miles, again reached 

 the ice-tongue, against which it built a distinct gravel plain. The 

 difference in elevation of the two ends of this channel is approximately 

 150 feet. This, in two and one-fourth miles, gives an ice slope of 

 sixty-seven feet per mile ; practically the same as that determined for 

 the Johnson Hollow channel. 



Remarks. — The condition favorable for the formation of a lateral 

 channel is the presence of an ice-tongue lying in a valley bordered by 

 hills. Under these conditions the marginal drainage is apt to be 

 diverted by any low gap in the valley sides, giving rise to a lateral 

 channel. It often happens that a stream after thus leaving the ice 

 finds itself in a valley tributary to that in which the ice-tongue lies. 

 It will then, after a longer or shorter course, return to the main 



