Pleistocene Papers^ Ottawa Meeting of G. S.A. 241 
[Continued from Pa^je 179.] 
PLEISTOCENE PAPERS READ AT THE OTTAWA 
MEETING OF THE GEOLOGICAL SOCIETY 
OF AMERICA. 
Eskers near Rochester, M. Y. By Warren TJpham. A very 
remarkable esker, called the Pinnacle hills, extending about four 
miles in a west- southwest course on the southeastern border of 
the cit}' of Rochester, and another esker series several miles 
farther southeast in Pittsford, were described in this paper and 
attributed to deposition by streams flowing down from the melt- 
ing surface of the ice-sheet during its departure, their channels 
having been enclosed on each side by ice and open above to the 
sky. The material of these eskers, which was shown to have 
been englacial, is chiefly gravel and sand, but also comprises in 
some parts of the Pinnacle hills very abundant and large boulders, 
up to ten feet in diameter, some of which are lifted 200 feet or 
more above their sources within a few miles on a nearly plain 
country. The near origin of the Niagara limestone boulders in 
these hills was noticed in their earliest description, which, with 
the flgure of a section, was published by Prof. James Hall fifty 
years ago. Probably no other locality has afl'orded so definite 
proof of transportation of drift into the lower part of the ice- 
sheet by currents having a considerable upward movement from 
a flat tract : but the angle of ascent may have been no more than 
one degree, or 92 feet per mile. An article by Mr. Charles R. 
Dryer, on the glacial geology of this region, with a map showing 
these eskers, is in the American Geologist, for April, 1890. 
President Gilbert and Secretary Fairoiiild spoke briefly, in 
discussion of this paper, concerning their observations of the 
peculiar structural features of the Pinnacle hills, for which no 
detailed explanation had been previously attempted. 
Comparison of Pleistocene and Present Ice-slieets. By Warren 
Upiiam. The Pleistocene ice-sheets of North America and Europe 
were compared with the now existing Maluspina, Greenland, and 
Antarctic ice-sheets, as to their areas, surface slopes and probable 
thickness, rates of erosion and ablation, sub-glacial and englacial 
drift, and manner of deposition of the various drift formations. 
The Malaspina glacier or ice-sheet, covered on its wasting borders 
by much drift and growing forests, is believed to afford explana- 
