SUMMIT LEVELS AMONG ALPINE MOUNTAINS 107 



The fact of accordance is established, while the theories of 

 explanation are very various. That they need critical examination 

 and sifting is clear, not only for the sake of the important fact 

 of accordance itself, but also for the reason that these theories 

 involve widely diverging views on great physiographic revolutions. 

 Geological history in long chapters is thereby as expressly implied 

 as it would be by the interpretation of purely stratigraphic evi- 

 dences, illustrating over and over again the truth that both classes 

 of evidences are required in building up a complete history of the 

 earth. Not only do these theories involve premises regarding great 

 denudations, but, as well, a multitude of details concerning river 

 history and the evolution of individual mountain massifs. There 

 are likewise involved correlative views of the physiographic develop- 

 ment of the neighboring regions, both on the large scale and in 

 details. Geographic description and nomenclature should be con- 

 trolled by reference to the correct theory or theories of land-form 

 origins. Finally, large conclusions concerning the origin of the 

 force of mountain uplift must follow in the wake of certain of the 

 hypotheses already announced to explain the phenomenon of accord- 

 ance in summit levels. The attempt has even been made to connect 

 the origin of fractures and of mineral veins with the specialized kind 

 of crustal movement hypothecated by one explanation of this accord- 

 ance. 1 There are thus abundant reasons for coming to a wise decision 

 as to the best explanation of the fact. 



THE VARIOUS EXPLANATIONS OF ACCORDANCE 



The hypotheses dealing with this sympathetic attitude of alpine 

 summits may be classified on the basis of the logical explanation of 

 an organism, (a) How far is the feature in question due to inheri- 

 tance ? (b) How far is it due to spontaneous development in the 

 present environment ? A review of the hypotheses shows, every- 

 where and naturally, emphasis placed on erosion, but the writer 

 believes that the possibilities of inheritance are only partially worked 



structures incidental to intense crumpling, metamorphism, and igneous intrusion as 

 exemplified in the Swiss Alps. 



1 A. C. Spencer, Transactions of the American Institute of Mining Engineers, 

 October, 1904, p. 35. 



