704 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



north of the main ridg-e are ordinarily but 10 to 20 feet in height, and the 

 ridging is far less conspicuous than in the main ridge. 



The sharply ridged parts of this inner border are confined chiefly to 

 the esker near Holley, the spur near Adams Basin, and the Pinnacle Hills 

 ridge in Rochester. 



The Holley esker sets in about a mile southwest of that village and 

 extends southwestward to within one-half mile of Clarendon, its length 

 being .about 1^ miles. It is a nearly continuous ridge, though it varies 

 greatly in height, there being hummocks on it. One^ of these hummocks 

 rises 40 feet above the adjacent parts of the ridge, while others rise 15 feet 

 or more. The ridge is in places very sharp, in one place its width being 

 only 30 or 40 yards and its height 20 to 30 feet. Along each side of the 

 ridge gravelly knolls abound, which rise 10 to 20 feet above the marshy 

 tract in which the esker lies. These knolls also extend around the southern 

 end of the ridge, being numerous at Clarendon and for a short distance south 

 and east of the village. 



The spur near Adams Basin does not carry a definite esker ridge, but 

 consists of irregular-shaped knolls, which are often gTOuped into small 

 clusters. The intricacy of contours is only faintly portrayed on the topo- 

 graphic map (PI. III). 



The Pinnacle Hills ridge, which received the attention of many geolo- 

 gists attending the Rochester Meeting of the Association for Advancement 

 of Science, in 1892, has since been described by Upham' and by Fairchild." 

 With a width of but one-eighth to one-half inile, including slopes, and a 

 height of 50 to 240 feet, it constitutes a very conspicuous drift feature. It 

 does not present the form of a typical esker, though it was put in this 

 category by Upham. Its topography is more like that of a very sharp 

 moraine, and the name kame-moraine given by Fairchild seems highly 

 applicable. The following description of the topography is taken from 

 Fairchild's paper just cited: 



The Pinnacle Hills extend from the village of Brighton to the Genesee River, a 

 distance of 4 miles, with a general direction of west 15° south. The belt of hills has 

 a linear form with a distinct curvature of large radius, the convexity facing south- 

 ward. The range, however, is not continuous or uniform, but consists of groups of 



^Eskers near Rochester, N. Y., by Warren Upham: Proc. Rochester Acad. Science, Vol. II, 

 1893, pp. 181-200. 



^The kame-moraine at Rochester, N. Y., by H. L. Fairchild: Am. Geologist, Vol. XVI, 1895, 

 pp. 39-.51; with map. 



