Carney — Possible Overflow Channel of Ponded Waters. 223 



and abraded these outlets ; still later during the recession 

 stage, it is probable that aggradation immediately from the ice 

 or by extra-morainic waters filled up the spillways to some extent. 

 A similar play of factors operated during each preceding ice- 

 invasion. With the weight given at present by glacialists to 

 the ice-erosion factor, it is probable that these outlets or cols 

 were appreciably lowered by even one advance of the ice. It 

 has been convincingly established that ice-erosion was effective 

 in the trough of Seneca valley.* 



All evidence, then, points to the conclusion that ice-front 

 waters of earlier invasions, as well as the pro-Wisconsin lakes, 

 flowed southward over cols or outlets at higher levels than did 

 the ponded bodies marginal to the receding Wisconsin ice. 

 The alternative hypothesis for channel No. 1 is that it was 

 associated in genesis with a lake held to a higher level than 

 that of Lake Newberry ; the divide somewhere between 

 Horseheads and Watkins has since been lowered. 



The list of channels in New York Statef made by waters 

 of the waning Wisconsin ice is long ; further detailed study 

 will reveal many more. An equal number of channel-ways 

 must have been necessitated in the advance of the Wisconsin 

 ice-sheet, and in both the advance and retreat of earlier ice- 

 sheets, provided the glacier moved as far over the area and then 

 retreated as deliberately as did the ice of the last invasion, and 

 provided further that glaciation produces but slight changes in 

 topographic relationships, a proposition on which there is 

 agreement.^ Such channels are short, being transverse to 

 divides. Conditions in later glaciation favored their oblitera- 

 tion possibly by ice-erosion, more probably by drift-burial. It 

 is conceivable that neither factor may have operated in every 

 case ; also that the retreating Wisconsin ice may have halted in 

 positions favorable to the resurrection of filled or partially 

 buried channels. Obviously channel No. 1 was used as a 

 spillway for the last high level lake of its altitude in Keuka 

 valley ; but at the present we find no satisfactory explanation 

 for the objections raised against its being associated genetically 

 with a lake held in front of the receding Wisconsin ice. We 

 believe that this channel suggests a pre- Wisconsin ice-invasion 

 of central New York.§ 



Department of Geology, Denison University, December, 1907. 



* Ibid., Journal of Geology, vol. xiv, p. 19, 1906. 



fH. L. Fairchild, Bull. Geol. Soc. Am., vol. x, pp. 60-61, 1899; ibid., 

 N. Y. State Mus., 20th Report of the State Geologist, pp. rll9-rl25, 1900; 

 ibid. N. Y. State Mus., 21st Report of the State Geologist, pp. r33-r35. 1901; 

 ibid.. N. Y. State Mus., 22d Report of the State Geologist, pp. r25-r30, 1902; 

 ibid., N. Y. State Mus., Bulletin 106, pp. 15-33, 1907; J. B. Woodworth, 

 1ST. Y. State Mus., Bulletin 83, pp. 16-24. 1905. 



% R. S. TaiT, The Physical Geography of New York State, pp. 104-5, 1902. 

 Chamberlin and Salisbury, Geology, vol. i, p. 275, 1904. 



§ Somewhat analogous evidence of multiple glaciation in New York was 

 presented in vol. xxiii, pp, 325-335, 1907, of this Journal. 



