mn 



THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Aet. XXIII. — The Diversity of the Glacial Period; by 

 T. C. Chamberlin. 



Iisr the November number of this Journal, there appeared 

 an article entitled " The Unity of the Glacial Epoch," by 

 Prof. G. Frederick Wright, that seems to call for a rejoinder, 

 partly to set right the personal views of ' some whose positions 

 are opposed, and partly to state with a greater approximation 

 to correctness the leading facts bearing on the question and 

 the necessary inferences from them. There are many ques- 

 tions relating to the problem that are legitimate subjects of 

 difference of opinion. Were the article confined to these, it 

 would be foreign to my habit to reply to it. Even as it is, if 

 this were the first or the second or the third discussion by the 

 author that has failed to correctly represent personal views and 

 scientific determinations, I should doubt whether I were justi- 

 fied in writing an article that must necessarily embrace a large 

 controversial factor. 



The article is not of the nature of a constructive advocacy 

 of the unity of the Glacial epoch, as its title seems to imply, 

 but an attempt at destructive criticism of the evidences ad- 

 vanced in support of the duality or diversity of the Glacial 

 period, and an attack upon the individual positions of some of 

 the advocates of these views. The insufficiency of all argu- 

 ments advanced for duality or diversity, even if demonstrated, 

 would, without positive arguments in proof of unity, only put 

 the question back where it was two decades ago. It would 

 make it simply a matter of doubt, with only conservatism on 

 the side of simplicity. That is an effort of doubtful utility at 



Am. Jour. Sci.— Third Series, Vol. XLV, No. 267. — March, 1893. 

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