t()6 kDCHESTER ACADEMY OF SCIENCE. fjatl. 9, 



water courses, like those of the ^'ahtse river and Fountain stream 

 described by Russell as flowing out from beneath the Malaspina 

 glacier. In these subglacial channels the streams must be building up 

 eskers, while gently sloping gravel and sand plains are being deposited 

 by the silt-laden waters in their course from the ice- front to the sea ('). 



Professor E. \V. Claypole drew a section of the marginal portion 

 of the ice-sheet, showing how, in his o[)inion, the Pinnacle hills were 

 formed by a stream which gathered drift from the melting ice surface, 

 and then fell through a crevasse and deposited the sand, gravel, and 

 boulders in a tunnel under the ice. 



Following these speakers, I remarked that the absence of any 

 covering of till upon the top and slopes of this esker, such as must 

 have fallen upon it from the englacial and superglacial drift of its roof 

 of ice if it were formed in a subglacial tunnel, leads me to believe 

 that its stream was wholly superglacial, and that the esker was depos- 

 ited in a deep ice-walled gorge, open above to the sky, eroded in the 

 border of the ice-sheet by the melting action of the running water. 



The purpose of the present essay will be completed by more fully 

 considering the probable manner of transportation of the many boul- 

 ders found in some portions of the gravel and sand of the Pinnacle 

 hills, the relationship of this esker to the lower morainic ridge con- 

 tinuous from it westward, the abrupt eastward ending of the Pinnacle 

 hills range, and similar features of the Pittsford esker series, with the 

 in(|uiry constantly in mind whether these features support the view 

 that these eskers were derived from previously englacial drift and 

 accumulated in superglacial channels. It will be needful at the same 

 time to consider the drainage from the ice-border in its relations to 

 the glacial Pake \V^arren and to the beginnings of Lake Irotpiois. 

 Beyond this we ought to learn, if possible, whether the same expla- 

 nation is generally apjilicable to eskers in other regions. 



The leading reason for our special interest in the Pinnacle hills is 

 the demonstrably near sources of their Niagara limestone boulders, 

 which have been transported only a few miles and yet were uplifted 

 at least loo to 200 feet into the ice-sheet from an approximately plain 

 country. Here we have a demonstration of the competency of the 

 glacial currents to gather drift into the lower part of the ice-sheet 

 from a nearly flat area, and we may understand how this takes place 

 by the differential movements of the upper, middle and lower portions 

 of the ice. Upon a belt of the ice-sheet extending many miles 



(i). Ff)r description of the present process of formation of eskers and sand plains by rivers 

 of the Malasi)ina glacier, sec RusscH's paper on " Mt. St. Elias and its Glaciers," Am. Jour. Sci., 

 III. Vol. X 1,1 II, pp. 169-182, with map, March, 1892 



