DISCUSSION CONCERNING FINGER LAKES 479 



year he recanted. Without inquiring what evidence had been found by 

 borings, or how much post-Glacial tilting had occurred, or if the hanging 

 valleys had buried predecessors, he declared Cayuga Lake to be a rock 

 basin. His dictum was based only on the occurrence of the modern 

 hanging valleys and their waterfalls. On the strength of this one fea- 

 ture he says : "As the tributaries of Cayuga River prove the rock basin 

 origin of Lake Cayuga, so also the Cayuga tributary to the Ontario 

 stream indicates that Lake Ontario is also rock basin.^ To this I replied 

 at the time.^ Later he says : "I am more than fully convinced that, 

 the two larger lakes (Cayuga and Seneca) are of the nature of rock 

 basins." ^° 



That he had not made an investigation of the pre-Clacial equivalents 

 of the hanging valleys is shown by his own words, writing ten years later: 

 "Though the existence of older gorges have been determined, in one or 

 two cases their abundance and their relationship to mature hanging val- 

 leys were not understood;" and "The theory of glacial erosion has been 

 held as the most rational explanation of the phenomena of the Finger 

 Lakes." ^^ At this time (1904) he published a reversal of this last conl 

 elusion, saying: "Until the facts opposing glacial erosion are explained, 

 or until the possibility of the rejuvination theory is eliminated, the cur- 

 rent theory of glacial erosion recently revived (largely by Tarr himself) 

 can not be established." ^^ Again Tarr wrote : "The fact that I have been 

 quoted as an opponent of the glacial erosion, which has not been the 

 case," etcetera; but he mentioned the occurrence of decayed rock at 

 Ithaca in evidence against the late glacial erosion of the Wisconsin epoch. 

 Now he falls back on an earlier period, saying: "There still remains some 

 evidence opposing glacial erosion, but none opposing erosion by an earlier 

 advance [of ice], unless the fact that no deposit of an earlier ice advance 

 are found in this region is opposing evidence."^^ Thus the author still 

 clings to his theory by falling back on negative evidence in an earlier 

 period, while abandoning his theory as inapplicable to the work of the 

 later Glacial period. Even the occurrence of one or two concordant trib- 

 utaries to the Finger Lakes, as mentioned by Tarr himself, should not 

 have been passed over, as these in themselves cast doubt on the theory of 

 glacial erosion, not to speak of the buried outlet at the northern end of 



8 Bun. Geol. Soc. America, vol. 5, 1894, pp. 339-356. 



» American Geologist, vol. 14, 1894, pp. 184-135. 



1" See his Physical Geography. 



11 American Geologist, vol. 33, 1904, pp. 277-291. 



" Journal of Geology, Vol. 14, 1906, pp. 18-21. 



" Ibl<3. 



