TYPES OF DRIFT 



629 



with "kettles," and not either feature alone, which is characteristic 



of terminal moraine topography. 



The "knobs" vary in size, from low mounds but a few feet 



Fig. 521. Drumlins in contour, near Clyde, N. Y. (U. S. Geol. Surv.) 



across, to hills half a mile or more in diameter, and a hundred feet 

 or more in height. Not rarely they are about as steep as the mate- 

 rial of which they are composed will lie. The "kettles" are the 

 counterparts of the elevations. They may be a few feet, or many 



