EROSION AND THE SUMMIT LEVEL OF THE ALPS 41 



to refer to the departure only as a modification of someone else's 

 earlier scheme without avowing that it is also a modification of 

 one's own. 



The further discussion of mountain carving in my "Erklarende 

 Beschreibung" postulates a cessation of upheaval about the time 

 that the sharp forms of maturity are reached; then follow in due 

 course, under the action of erosion alone, the rounded or subdued 

 forms of late maturity and the worn-down forms of old age. It is 

 the prolongation of upheaval after sharp-crested forms are reached, 

 as postulated in Penck's first ideal cycle, and the development of a 

 stage of balance between upheaval and degradation with a resulting 

 maintenance for a time of a constant summit altitude and a 

 constant relief that constitute real advances in Penck's treatment 

 of the erosion cycle; but not also, as he implies, the discussion of 

 the interaction of upheaval and erosion during the attainment of 

 sharp-crested forms. The advances are surely valuable and 

 interesting, even though, as pointed out above, some of the deduc- 

 tions which they include seem, in the absence of full explanation, 

 somewhat insecure. 



Closing remarks. — The composition of the three parts of this 

 article has been attended with mixed feelings. The analysis of 

 Penck's "Gipfelflur" essay in the first part was a pleasant duty 

 in so far as it was concerned with the constructive side of his duty. 

 The general review and summary of the scheme of the erosion 

 cycle in the second part was also an agreeable task, as it brought to 

 mind memories of work and progress in association with many 

 colleagues through forty years of busy life. The correction of 

 Penck's corrections in the third part was a disagreeable necessity. 

 It would not have been undertaken but for his exceptional rank as 

 a geographer and for the high standing of the Academy in whose 

 proceedings his essay is pubHshed. On both those grounds it has 

 been deemed desirable to show that his adverse criticisms are much 

 less pertinent to my treatment of the erosion cycle than a reader 

 of his essay would be led to suppose, and that the real value of 

 his essay, which is unquestionably large, lies in the extension of the 

 deductive treatment of the erosion cycle with especial respect to 

 a mature stage in which upheaval and erosion are balanced. 



