208 ROCHESTER ACADEMY OF SCIENCE. 



the deep east-west valley through which the Buffalo branch of the 

 Lehigh Valley railroad passes. 



Three-fourths of a mile sovith of Cedar Swamp there occurs a 

 low but well-defined esker which may be regarded as a tributary. 

 It is on the east side of the railroad and extends at almost right 

 angles to the course of the main esker. It is several rods long but 

 nowhere more than 10 feet in vertical section with uniform gentle 

 slopes. There is no evidence of its continuation west of the railroad 

 track where it might be expected to join the main esker ridge. 



An excavation near the southern terminus of the esker reveals 

 something regarding its internal character. Here boulders rounded 

 and of all sizes occur in profusion. The gravel is for the most part 

 of poor quality by reason of the large quantity of coarse materials, 

 that of better grade being located in the center of the pit extending 

 from the base of the excavation to the crest of the esker. On each 

 side of this coarse materials predominate. At least 50 per cent, of 

 the material is ^Medina, while 15 to 20 per cent, is crystalline. Strati- 

 fication is not apparent. The base of the pit does not go below the 

 adjoining surface so that it is impossible to tell how deeply the 

 esker characters penetrate. 



Origin. There are few features of this esker that shed light 

 upon the manner of origin, the steep slopes and gravelly surfaces 

 are characteristic of practically all eskers, the composition and char- 

 acter of course are likewise typical of the majority of eskers. The 

 long interruptions at the north end of the esker may be due to sub- 

 sequent erosion or to lack of deposition in the glacial stream. The 

 short tributary is likewise noncommittal as to origin, the absence 

 of till from the esker surface may be due to subsequent erosion or 

 lack of deposition at the time of esker formation, or possibly to other 

 causes. Its trend along the axis of a narrow valley in the direction 

 of ice movement would seem to indicate its formation in a subglacial 

 stream following the lowest part of the valley during or just after 

 the accumulation of the heavy drumlin masses on either side. 



Cartersville esker. Figure 6. The best known and one of the 

 most magnificent eskers in Western New York lies nearly opposite 

 Cartersville and north of Bushnells Basin. It has been briefly men- 

 tioned by Dr. Dryer (30), and more recently more fully described 



