ESKERS AND FRONTAL TERRACES. 23 



vary from 20 to 32 degrees. The top in places is narrow and sharp, 

 elsewhere rounded, and is occupied for nearly a half mile by the high- 

 way of the valley.* The surface is quite rough with boulclerets, and a 

 considerable talus of such material lies at the base of one of the steeper 

 sections. The valley appears to be continuous with the course of an- 

 other stream to the south, thus furnishing free outlet for the subglacial 

 waters, which were the agent of deposition. 



FRONTAL TERRACES. 



The most important structures of this class are at Solsville, where they 

 stretch away from the great kame moraine already described. They lie 

 just north of the divide, so that, while their surfaces slope gently west- 

 ward, the narrow path of Oriskany creek descends between, in the op- 

 posite direction. The kames on both sides graduate down into the 

 terraces, which in turn are pitted in their upper portions, but smooth 

 and uniform toward their distal extremities. The marginal slopes range 

 from 20 to 25 degrees. 



The northern terrace is nearly two miles long and varies from one- 

 fourth to one-half mile in width. A short lateral valley from the north 

 is graded up to its level both by ponding and silting and by intrusion 

 of the waste from the main valley. Farther west the terrace pushes 

 nearly across the valley of Oriskany creek, which here enters from the 

 northwest. This headwater, like several others near by, has been pirated 

 from the Chenango by the swifter northern streams. The terrace is here 

 smooth and benched toward the main valley, but morainic in surface 

 expression on the side looking up the tributary valley. Where the ter- 

 race springs from the moraine at Solsville its height is 70 feet. At the 

 west end it is 45 feet. The difference is due to the gentle descent of its 

 surface westward and the opposite fall of the course of the existing 

 stream. 



The southward terrace is nearly three miles in length and a mile in 

 greatest width. A rather abrupt turn of the valley southward swung 

 the current in that direction and prolonged this terrace beyond its com- 

 panion. It also is 70 feet high where it joins the moraine, but descends 

 more rapidly than the other, and terminates upon the divide with an 

 altitude of 18 feet. Its frontal and terminal slopes at and south of 

 Boackville have an average inclination of 18 degrees and are decidedly 

 lobate in form. Madison lake, three-fourths of a mile long, one-fourth 

 of a mile wide, and said to be 75 feet deep, lies in an elongated kettle- 

 hole in the body of this terrace. Its water-level is 16 feet above the ad- 



* Some typical Eskers of southern New England. J. B. Woodworth ; Proc. Boston Soc. Nat. 

 Hisi., vol xxvi, p. 215. 



