250 bulletin: museum of comparative zoology. 



wall. One of the best defined ridges, at an elevation of twelve hundred 

 feet, is from twenty to fifty feet high and some four hundred yards in 

 length. The longitudinal and transverse profiles are in every way similar 

 to those of a Swiss lateral moraine. Though generally arranged parallel 

 to the valley-wall, in some instances the moraine is winged out from it 

 and is then characterized by many shallow kettles and small ponds. The 

 general slope of the moraine-crests is to the southward toward Nachvak 

 Bay, and is sympathetic with the inclination of three well-marked rock- 

 benches on the east side of the Kogarsuk Valley. Combining the evi- 

 dence of groovings with these facts, it was evident that the glacier that 

 was responsible for the moraines and benches flowed southward toward 



Figure 3. — Cross-section of the Kogarsuk Valley showing its bed-rock floor overlain 

 by lateral moraines (solid black) and trenched ground moraine (dotted lines). Kock- 

 benches on the right. Lookiug north. 



the great fiord. At twelve hundred and fifty feet on the flat top of the 

 long spur which lies in the angle between the fiord and the brook, a 

 crescent-shaped frontal moraine nearly four hundred yards in length 

 lies, as it were, stranded there, as the Kogarsuk glacier retreated to its 

 narrower channel on the east. 



The belt of lateral moraines, here and there broken down in the 

 paths of entering side streams, extends five miles to the northward from 

 its southern extremity. A little more than three miles from the 

 mouth of the brook, the valley widens out in a notably flat stretch 

 estimated to be at least eight miles in length and from one to three miles 

 in width. The bed-rock is here deeply buried in a till-deposit which 

 seems to be transitional into the terraced lateral moraines on the we&t 



