l82 ROCHESTER ACADEMY OF SCIENCE. [Jail. 9, 



given to discussion of the manner of its formation through the agency 

 of the ice-sheet and the streams produced by its melting. Before 

 stating some of the opinions brought out in that discussion, and 

 attempting a full inquiry concerning the processes of accum.ulation of 

 this and other eskers and kames, we will first go again, as I did on 

 following days, over the Pinnacle hills and describe their contour and 

 numerous sections exposed by excavations for road material and 

 for the passage of streets. The other drift deposits and contour of 

 their vicinity will be noted, and a second series of eskers lying several 

 miles farther southeast in Pittsford, which I also examined, will be 

 described, with their relationship to prominent drumlins near, and to 

 terminal moraines more remote, on the south. 



Description of the Pinnacle Hills. 



From Brighton village and station on the New York Central rail- 

 road, three miles southeast from the station in P^ochester, this promi- 

 nent range of hills extends in an almost straight course about four 

 and a half miles west-southwesterly to the Genesee river close south 

 of the State dam. In passing the east end of this esker, the Erie 

 canal turns from a due east to a due south course. Along its first 

 mile from Brighton the esker rises 75 to 150 feet above the country 

 on each side, and declines in height from 125 to 75 feet near the 

 western end of this portion, where it is known as Cobb's hill. Imme- 

 diately to the west, near the residence of Mrs. W. H. Cobb, a sag in 

 the esker, as it was originally, before being cut down for the extension 

 of Monroe avenue, had a height of only about 50 feet. Next west- 

 ward the esker rises in the distance of a half mile to its highest point, 

 called the Pinnacle, 200 feet above the nearly plain region on the 

 north and south. Thence the continuation of the esker along its next 

 two miles, varying in altitude mainly from 150 to 100 feet above the 

 general level, is occupied, in order from east to west, by the St. 

 Patrick Cemetery, the Highland Park, which includes the Mt. Hope 

 reservoir in its western part, and the extensive Mt. Hope Cemetery. 

 In its next mile west to the river, the ridge is lower, having a height 

 of only 80 to 50 feet above the State dam. The northeastern end of 

 this hill range at Brighton is very definite, overlooking a wide expanse 

 of the low land ; but its western end is indefinite, for in the line of 

 its continuation west of the Genesee it is represented along a distance 

 of at least two miles (which is as far as my examination extended) by 

 a low ridge, mostly 30 to 40 feet above the general level. Between 



