l86 ROCHESTER ACADEMY OF SCIENCE, [Jan. 9, 



the gravel and small rock fragments are rounded or at least much 

 worn on their edges and corners. 



Other sections which were examined in our excursion on the 

 northern slope of the esker near this place and about a quarter of a 

 mile to the northeast, show the same astonishing profusion of boul- 

 ders with the upper coarse gravel, underlain by beds having fewer 

 boulders. The gravel and sand are characterized by irregular and 

 often oblique bedding, variable thickness of individual layers, and 

 occasional oblique or nearly vertical faults with small amount of dis- 

 placement ('). Boulders are also strown in considerable numbers on 

 the surface of this part of the esker, but elsewhere along most of its 

 extent they are usually rare both on the surface and in excavations. 

 Mr. Gilbert called attention to the origin of the boulders, and pointed 

 out the very significant fact that many of them are of the Niagara 

 limestone, which can have been transported no more than three or 

 four miles from its parent ledges, since the northern limit of this 

 formation lies within that distance. Some of these boulders were 

 seen on or near the Pinnacle, at least 200 feet above the outcrops on 

 the plain country northeastward from which they must have been 

 derived. 



Continuing over the Pinnacle and through the Highland Park, I 

 examined numerous sections, all of which were interbedded gravel 

 and sand with only very rare boulders or more commonly none. Occa- 

 sionally, however, a boulder 5 or even 10 feet in diameter is found on 

 the surface, or in a section, remarkably in contrast with the water- 

 deposited sand and gravel, in which the largest pebbles and cobbles 

 range from a few inches to a foot, or seldom one and a half feet in 

 diameter. From the Pinnacle to the Mount Hope cemetery, most of 

 the excavations are chiefly sand. 



The cut made west of this cemetery by a branch of the New 

 York, Lake Erie «S; Western railroad has a length of nearly a quarter 

 of a mile from north to south and is from 15 to 25 feet deep. Large 

 portions of this section are true till, or clay, sand, and small and large 

 rock fragments, mingled in an unstratified deposit ; but, like the till 

 of the surrounding country, it contains only few large boulders. 

 Among the half dozen boulders of greater size than two feet in 

 length seen in the eastern face of this excavation, one of the largest, 

 about five feet in diameter, was Niagara limestone. With the depos- 



(i.) Numbers 323, 324 and 325 of the list of photographs of the Geoloffical Society of 

 America (^Bulletin, G. S. A., Vol. Ill, p. 472) are views of sections of the Pinnacle hills esker at 

 this locality, photographed and presented by Professor H. L. Fairchild. 



