OPINIONS O^ PREVIOUS WRITERS. 345 



• 



Foote* adopts very nearly the same line of argument, stating that he 

 will not consider " whether the glacier or iceberg theory is the more 

 probable," although he believes that both agencies were employed. He 

 believes that the valleys were made into fjords b}^ wave action when the 

 land was elevated, and that they had an outflow to the south. These 

 valleys " were probably much deepened b}^ the gouging action of the 

 lobes of the general ice-sheet which flowed down their channels." 



Writing in 1880, Carll f says of the Great lakes, and presumably also 

 of these lesser lakes, that '' the basins of the Great Lakes were formed by 

 the widening and deepening of old river valleys through the agencies of 

 ice and sub-glacial water." Shaler,! following Ramsay, says ''the lakes 

 of Switzerland, [and] those of New York and New England, are good 

 and familiar instances of this work " — glacial erosion. 



On the other hand, Spencer § arrives at the opposite conclusion, for 

 he says : 



'* Though the bottoms of these lakes (Finger lakes) are frequently below the sea 

 level, yet in no case, that I am aware of, are they nearly as deep as lake Ontario. 

 Doubtless these small lakes were former expansions of the rivers running into lake 

 Ontario in Preglacial times, and owe to ice, simply, the closing of their outlets by 

 drift." 



Professor Davis || partly agrees with Spencer, and writes of lake 

 Cayuga as follows : 



" Its trough was cut by an old stream flowing from the New York and Pennsyl- 

 vania plateau, northward into lake Ontario, at a time when the drainage of the re- 

 gion ran in channels considerably below present river-levels; glacial erosion has 

 probably smoothed and deepened it, but to suppose it entirely so formed would 

 imply the production of a tongue of ice from the front of the old glacier, peculiar in 

 form and remarkable in erosive power; the supposition that it is the result of 

 down faulting or local subsidence, is negatived by the absence of disturbance in the 

 neighboring hills ; to call it a rock basin is entirely unwarranted, for its prolonga- 

 tion north of the lake is across a great drift-area, without rock in place. The form 

 of the trough is different in no important particular from valleys of evident erosion 

 in non-glaciated regions." 



In the next descriptions we find the opposite view stated, and in this 

 connection Johnson ^ says — 



"That these lake basins were excavated bv glacial action, seems almost self- 

 evident, and is, indeed, almost universally admitted. Their radiated arrangement, 



* Notes upon the Geological History of Cayuga and Seneca Lakes, 1877. 



tGeol. Survey of Pennsylvania, III, 1880, p. 331. 



t Illustrations of the Earth's Surface, 1881, p. 52. 



§ Proc. Am. Phil. Soc. vol. xix, 1881, p. 333. 



II Proc. Bost. Soc. Nat. Hist., vol. 21, 1882, p. .359. Professor Davis has a very important paper on 

 "Giaeial Erosion" in the next volume, 22, pp. lO-.'iS, in which the subject of roeli basins is dis- 

 cussed on page 50. 



^.■Vnnals New York .\cad. Sci., vol. li, 1882, p. 2G0 ; see also Trans. N. Y. Acad,. Sci. vol. i, 1882, p. 78. 



