412 



NEW YORK STATE MUSEUM 



It will be noted that only two drumlins in the above table lift 

 their summits 200 feet above their platform, though several approach 



that hight. 



The length of the drumlins is quite as variable as their hight, but 

 it can not be well determined from the map contours, as a relief of 

 less than 20 feet may carry a distinct ridge for a long distance. 

 The long ridges of drumlinized drift which specially characterize 

 the drift surface in the northwest corner of the State, including the 

 Niagara-Genesee prairie, are almost unrecognized by the topographic 

 map. ' ^ 



Scores of drumlins can be found on the map w4th a contoured 

 length of a mile, or even a mile and a quarter. A length of 1% 

 miles is not rare, but 2 miles is extreme. Perhaps the longest well 

 contoured forms are in the Oswego district, shown in plate 6. 



The very long drumlins are sometimes produced by the close 

 welding of overlapping ridges. 



Composition and structure 



The material composing the New York drumlins' is very compact 

 till. The writer recollects only one or two instances in which water- 

 laid drift has been found unequivocally incorporated in the drumlin 

 mass. Gravel and sand are frequently found on the flanks of the 

 drumlins, specially where they were exposed to wave work of the 

 glacial lakes, but the experienced observer could never mistake this 

 for drumlin material. Water-laid drift may be expected on the 

 surface of the drumlins as an occasional product of superficial 

 stream work at or near the ice border. In morainal areas the 

 marginal drift, kame or till, may be scattered on and among the 

 drumlins, and sometimes in such abundance as to obscure or per- 

 haps partially bury the drumlin forms. Such a case is found in the^ 

 Junius kame moraine, midway betweeii Geneva and Lyons. How- 

 ever, this superficial morainal drift must not be mistaken for nor 

 confused with the drumlin material, as it is not only emphatically 

 distinct in its genesis from the subglacial drumlin mass but sub- 

 sequent in time of deposition. 



Only two instances have been found by the writer of water-laid 

 drift distinctly within the drumlin mass. In the northeast edge of 

 the village of Lyons, on Phelps st., a small drumlinlike ridge of till 

 about 500 feet long and 150 feet wide, lying on the east flank of a 



