246 



SCIENCE 



[N. S. Vol. XXXVII. No. 946 



the south edge of the belt they are slender 

 ridges and flutings, too attenuated to be 

 represented by the twenty-feet contours of 

 the topographic sheets. It would require 

 at least five-feet contours to show the fron- 

 tal drumlinized surface. Two miles in 

 front of the most southerly ridges indicated 

 on the Geneva sheet lies a weak but definite 

 moraine. It is weak because the ice had 

 plastered its load of drift into the drum- 

 lins. 



From the relation of the ice front to the 

 glacial waters and other data it has been 

 roughly estimated that the thickness of the 

 ice over the middle of the drumlin belt was 

 about 900 feet, or more than 700 feet over 

 the tops of the highest drumlins. 



Marginal: Moraines. — The only map 

 published to the present time that shows 

 moraines in detail is that by Tarr in the 

 Watkins Glen-Catatonk folio (No. 169), 

 which is accompanied by good description. 

 This map, Surficial Geology, covers eight 

 quadrangles of the south-central portion of 

 the state and includes the upper (southern) 

 ends of the Seneca and Cayuga valleys. 

 Except a few fragmentary moraines in the 

 east and west stretch of the Susquehanna 

 and Chemung valleys there are almost no 

 moraines south of the divide, as already 

 noted in this writing. The lines of drift 

 massing show decided lobation of the ice in 

 the valleys north of the divide and con- 

 formity to the land surface. The plastic 

 ice was here flowing on its own deposits and 

 had no erosive power. Probably the only 

 moraines in the state that can properly be 

 called "lateral" lie in these valleys. 



In the west half of the state the heavier 

 or more conspicuous morainic belts have 

 been approximately located though little 

 precise mapping has been attempted. The 

 most recent and definite is by Leverett," 

 and a sketch map, Fig. 11, page 15, in the 



"U. S. Geol. Surv., Monograph XLI., 1902. 



Folio 169. These morainic belts clearly 

 show the larger lobation of the waning ice 

 sheet in the Ontario and Erie basins. 



In the east half of the state the moraines 

 have been located in only few places, ex- 

 cepting the terminal moraine. In the 

 Hudson and Champlain valleys Woodworth 

 has recognized some fragments and ice-con- 

 tacts. This difference in moraine develop- 

 ment between the two parts of the state 

 is due to the difference in the gross topog- 

 raphy. A glance at the map shows that 

 on the Hudson-Champlain meridian the 

 distance covered by the receding ice front 

 is greater than in the Ontario basin, so 

 spreading the drift over more area. The 

 rocks in the east part of the state are more 

 resistant to erosion, due to kind and struc- 

 ture. The Hudson ice lobe and its suc- 

 cessor in the Champlain Valley were al- 

 ways faced by ocean waters and the termi- 

 nal drift in the bottom section of the great 

 valley was mostly scattered and buried 

 under the water deposits. On the high 

 grounds east and west of the marine inlet 

 the surfaces are so rough, or even moun- 

 tainous, that the moraine deposits lack 

 continuity and volume. It wdll be very 

 difficult to trace morainic belts across the 

 Hudson-Champlain Valley with certainty, 

 though it is important to know the lines of 

 the receding ice front. 



WORK OP GLACIAL WATERS 



Erosional Work of Streams. Normal 

 Drainage. — It is apparent that the flow 

 of glacial waters freely away from the 

 ice could occur only south of the divide, 

 and as the present divide was established 

 by morainal filling and lies north of the 

 preglacial divide much of the southward 

 flow was drainage of ice-dammed waters, 

 and that some of the present south-leading 

 channels were cut by the glacial waters. 

 The preglacial flow oi, the main streams 



