no REGINALD A. DALY 



dissection of the former lowland will greatly weaken the proofs of 

 approximate planation near base-level at the end of a former physio- 

 graphic cycle. It is expected, however, that subequality of accord- 

 ance of summit levels will long characterize the individual mountains 

 produced by the intaglio cutting of the upwarped peneplain. Con- 

 versely, where such accordance of summit levels in structurally com- 

 plex mountains is found, it is legitimate, if not necessary, to place 

 ancient peneplanation as a possible stage in the topographic evolution. 



This has been the principal criterion on which Messrs. Russell, 

 Smith, and Willis have based wide-reaching conclusions regarding 

 the development of the main Cascade Range of Washington. Mr. 

 Willis has mapped a few, very small, flattish areas on summits which 

 he considers as possible remnants of the peneplain. 1 Mr. Smith 

 states that no remnant of it has been discovered in the large area of 

 the Snoqualmie Quadrangle (U. S. Geological Survey map) which 

 he has particularly studied. 2 Mr. Russell came to a similar conclu- 

 sion regarding the high Cascades of northern Washington. 3 Geology 

 and physiography owe much to these authorities for their systematic 

 and masterly presentations of the theory which every worker in the 

 general geology of the Cascades must entertain and carefully discuss. 

 The problem is there, as in other similar ranges, peculiarly difficult 

 because it is precisely in mountains of alpine height that the records 

 of former peneplanation are most quickly rubbed out; it is there that 

 positive criteria are reduced to a minimum. One must therefore 

 especially welcome such constructive work as is represented in the 

 memoirs recently published concerning a typical alpine range, the 

 high Cascades. 



The peneplain theory does certainly render the accordance of 

 summit levels among alpine peaks intelligible. Yet that fact is far 

 from proving the truth of the theory as applied to alpine ranges. 

 This will be especially clear if it can be shown that there are, and 

 have been, other agencies at work capable of producing the actual 

 degree of accordance in the summit levels of such a range as the high 

 Cascades. The writer believes that further constructive work along 



1 Professional Paper No. IQ, U. S. Geological Survey (1903), Plates 16 and 17. 



2 Ibid., p. 34. 



3 Twentieth Annual Report, U. S. Geological Survey, Part II (1900), p. 141. 



