192 ROCHESTER ACADEMY OF SCIENCE. [Ja^- 9, 



Between 35 and 60 miles south of Rochester, conspicuous termi- 

 nal moraines run approximately from west to east, as described and 

 mapped by Professor T. C. Chamberlin ('). On the meridian of 

 Rochester these moraines are somewhat interblended, fragmentary, 

 and irregular in their development upon a width of nearly 25 miles 

 from the southern ends of Conesus and Hemlock lakes southward to 

 the vicinity of Hornellsville. Farther to the east, for a distance of 

 about 150 miles, to the Catskill mountains and the Mohawk river, 

 they are more distinctly developed as two morainic belts, of which the 

 southern one is traced in a slowly curving course, convex toward the 

 south, along the valleys of the Canisteo, Tioga and upper Susque- 

 hanna rivers, while the northern one passes in a more sharply curved 

 and lobate course by the south ends of the Finger lakes to Ilion and 

 Herkimer on the Mohawk. In the valleys extending southward from 

 the heads of the larger Finger lakes the thickness of the northern 

 moraine appears to be several hundreds of feet, and in the case of 

 Seneca lake perhaps more than 1,000 feet ; but on the intervening 

 plateaus the thickness of the morainic drift is comparatively insig- 

 nificant, averaging probably no more than 25 to 50 feet upon widths 

 varying from one to two or three miles, 



A more distant moraine, however, lying on and near the bound- 

 ary of the glacial drift, extends from the vicinity of Salamanca, N. Y., 

 east-southeasterly to the Delaware river at Belvidere, N. ]., and to 

 Staten Island, the Narrows, and Long Island. This moraine, 

 described in Pennsylvania by Professors Lewis and Wright, (') passes 

 about 100 miles south of Rochester. 



Relatio?iship to Glacial Movements. — The currents of the ice-sheet 

 flowed perpendicularly toward its boundaries and marginal moraines, 

 that is, to the south or somewhat west of south for the region about 

 Rochester and Pittsford ; but during the recession of the ice from 

 that area, its currents were in some portions deflected much to the 

 west, because of more rapid melting of the ice on that side and con- 

 sequent indentations or embayments in its border. This faster melt- 

 ing on the west was probably at first due in large part to the laving 

 action of the glacial Lake Warren, which extended from the Avestern 

 part of the basin of Lake Ontario over the upper Laurentian lakes, 

 outflowing at Chicago to the Des Plaines, Illinois, and Mississippi 

 rivers ; and in the later stage of the glacial recession when the Roch- 



(I.) Third Annual Report of the U.S. Geol. Survey, for 1881-82, pp. 351-360, with Plate 

 XXXIII. 



(2.) Report Z, Second Geol. Survey of Pennsylvania. 



