2 W. M. DAVIS 



PART I. PENCK'S essay ON THE SUMMIT 

 LEVEL OF THE ALPS 



A leading feature of the Alps. — -An essay entitled "Die Gipfelflur 

 der Alpen" by Professor Albrecht Penck' is of special interest on 

 several counts. It discusses a striking feature of the most studied 

 mountains in the world; it is written by the most accomphshed 

 geological geographer of Europe, whose acquaintance with his 

 field is exceptionally intimate; it proposes several refinements of 

 the cycle of erosion; and it employs deduction to an extent that, 

 while unquestionably helpful, has been decried by certain other 

 German geographers. 



The subject under discussion is the relative constancy of altitudes 

 in the higher ridges and peaks of the Alps. If one stands on a 

 main summit, countless other summits rise like waves of the sea 

 with crests of similar heights, in spite of the very dissimilar heights 

 that the summits should have if they still represented the unequal 

 deformational upKfts that the different parts of the range have 

 suffered. Penck himself over thirty years ago explained the similar 

 summit altitudes as marking an "upper Hmit of denudation," 

 above which a mountain top could endure so short a time under 

 the violent attack of the weather and the active removal of detritus 

 on the over-steep slopes as to be rare occurrence.^ He now extends 

 his previous discussion, first by a more refined account of Alpine 

 forms, in which he introduces an understanding of the effects of 

 glacial erosion that had not been reached when his earlier article 

 was written, and second by an elaborate deductive analysis of the 

 cycle of erosion for mountains, in which the interaction of upheaval 

 and degradation is more fully considered than has hitherto been 

 done. His analysis is summarized in the following paragraphs, to 

 which my comments are added in parentheses. 



The preglacial form of the Alps. — ^The study of actual Alpine 

 forms leads Penck to the conclusion that, as a rule, even if a typical 

 mountain ridge were restored from its present extremely sharp form 

 as given by glacial erosion to its preglacial form, its crest would have 



^ Sitziingsher. prenss. Akad., XVII (Berlin, 1919), pp. 256-68. 

 ^"Uber Denudation der Erdoberflache," Schr. Ver. Verbr. nat. Kenntn., Vol. 

 XXVII (Vienna, 1887), p. 431. 



