ESKERS IN THE VICINITY OF ROCHESTER, NEW YORK. 233 



sand. Large boulders are rare. Till occurs locally. Excavations 

 have been made in several places, the most recent of which exhibit 

 fine gravel, poorly stratified, covered by till to a depth of four feet. 

 This excavation occurs along the north-south road at the north end 

 of the southern half of the esker. 



This ridge lies north of the Barre moraine which is very in- 

 definite through this portion of Monroe County and the adjacent 

 part of Orleans county, consisting chiefly of low, irregularly 

 distributed mounds and short ridges. 



Origin. It is quite possible that this ridge may be interpreted 

 in another way rather than as constituting an esker. Its width, its 

 very gentle slopes and its material are not typical of eskers. In fact 

 the southern segment resembles a drumlin as seen from the north 

 and from the sides. It has the same trend as the drumlins of this 

 area. The topographic map exhibits this similarity very strikingly, 

 however, its composition of sand with some gravel is opposed to this 

 interpretation of its origin. 



Again this feature may be considered as a morainic spur extend- 

 ing northward from the Barre moraine. 



Finally it may be interpreted as an esker built in a very broad 

 subglacial stream at the time of the deposition of the Barre moraine, 

 or, less likely, the filHng by a powerful stream of a broad re-entrant 

 of the ice extending back from the Barre moraine. 



Conclusion. 



The study of the eskers in the vicinity of Rochester has de- 

 veloped few new facts and the observations recorded exhibit few 

 new features. Each esker possesses its individual peculiarities which 

 are largely a matter of detail. The relations at the point of origin, 

 the relation at the termination, the character of the course, the rela- 

 tion to surroundings, the composition, are essentially the same with 

 the New York eskers as characterize eskers in other regions. 



The features exhibited by the western New York eskers seem 

 to indicate in a vast majority of instances an origin in a tunnel be- 

 neath the ice. It is true that the characteristics of some eskers do 

 not throw much light upon the manner of their origin, yet in the 

 case of most eskers, if they are studied carefully, there will be 



