4IO NEW YORK STATE MUSEUM 



in their growth or even blended. Asymmetry may be due to some 

 local variation in the ice movement, apart from the crowding in 

 construction. 



Sometimes the drumlins have an outline when seen endwise that 

 resembles the normal longitudinal profile. This abnormal form has 

 been seen frequently in Wayne county west and northwest of Wal- 

 worth [pi. 15]. This form is not due to change of ice flow direction 

 (which accounts for the similar appearances in the Pulaski district) 

 but to irregular construction, and perhaps to ultimate union of 

 primarily distinct drumlins. In the dominant drumlinarea the grow- 

 ing drumlins seem to have frequently fused together so as to give 

 unbalanced cross-section profiles, but such drumlin masses have in 

 longitudinal 'outline the characteristic curve. 



Dimensions. The size and dimensions of drumlins are variable, 

 within limits, according to the quantity and quality of the drift and 

 the depth and impulse of the ice sheet. The smaller or infantile 

 drumlins do not usually have good or characteristic forms unless 

 they are of the slender type or small, attenuated ridges, which may 

 be small in cross-section and yet retain a distinctive character as 

 ice-molded till. 



There seems to be a limit to the hight of individual drumlins, this 

 being in New York about 200 feet. Using the map contours for 

 determining the base of the drumlin as well as the summit altitude 

 (an inexact basis, with maximum error of 40 feet) only one drumlin 

 is found with altitude over 200 feet. At some point the upbuilding 

 process is antagonized by the eroding or leveling tendency and a 

 balance is struck between the opposing forces which limits extreme 

 hight, and results, apparently, in the production of multiple ridges 

 of moderate size instead of one huge ridge. This principle seems 

 to be illustrated in the form of the peculiar groups in the Syracuse 

 region, described later [p. 429 and pi. 9]. 



The most conspicuous drumlins, striking because of their isolation, 

 like those rising out of the Montezuma marshes, are not the highest. 

 Using the map contours, as noted above, for approximate data along 

 with the figures frequently given on the map for definite altitudes 

 of many higher drumlins, the following table has been compiled. 

 This gives the approximate altitudes of base and summit and the 

 individual hight of a considerable number of New York drumlins 

 in different districts. 



