EROSION AND THE SUMMIT LEVEL OF THE ALPS 17 



examples of these various kinds of forms. Consequent, obsequent, 

 and resequent may also be advantageously used in the explanatory 

 description of scarps on faulted structures, with particular relation 

 to later cycles of erosion than the one introduced by the faulting/ 

 The failure to distinguish between consequent fault scarps and 

 resequent or obsequent fault-line scarps has sometimes led to errors 

 as serious as those resulting from the failure to recognize subsequent 

 valleys as constituting a class by themselves, altogether unlike in 

 origin to antecedent, consequent, and superimposed valleys. It is 

 significant that Powell's terms, anaclinal, catacKnal, etc., which he 

 invented to express empirical relations between streams and 

 structures, have been little used as compared to the terms of the 

 sequential series.^ A preference is thus implied for terms that ex- 

 press genetic relations. 



The term grade, used to describe the smoothed courses of 

 mature and old streams that are neither wearing down nor building 

 up their beds, is due to an oral suggestion by Gilbert. It stands 

 nicely between the long familiar term, degrade, and Salisbury's 

 newer term, aggrade; and it may be as well applied to sheets of 

 waste on soil-covered hill sides, as to streams of water in smooth 

 valley bottoms. The same term also serves properly in connection 



' "Nomenclature of Surface Forms on Faulted Structures," Bull. Geol. Soc. Amer., 

 Vol. XXIV (1913), pp. 187-216. 



^ A number of elaborate explanatory terms have been suggested without reaching 

 general acceptance. Lowl's terms, symptygmatisch, bikataklastisch, pseudotektonisch, 

 etc., for the descriptions of valleys (Ueber Talbidimg, Prague, 1884) have not come into 



, use. Penck's terms, homogenetisch and homoplastisch, for forms of similar origin 

 and of similar shape ("Die Geomorphologie als genetische wissenschaft," Ber. 6ten 

 Internal. Geogr. Kongr., London, 1895), are rarely encountered. Passarge's mono 

 dynamische and polydynamische Einzelformen (" Physiologische Morphologie," 

 Milt. Geogr. Ges., Vol. XXVI, Hamburg, 1912) and Falconer's exogenetic positive or 

 negative forms and endogenetic negative tangential fracture landscape forms ("Land 



• Forms and Landscapes," Scot. Geogr. Mag., Vol. XXXI, 1915; see pp. 394-401) are 

 seldom if ever quoted by others than their authors. Among my own proposals that 

 have not been later used even by myself are compoimd, complex, and composite, as 

 names for rivers of different origins ("Rivers and Valleys of Pennsylvania," Nal. 

 Geogr. Mag., Vol. I [1889], 183-253; see p. 219). Whether morvan ("Relation of 

 Geography to Geology," Bull. Geol. Soc. Amer., Vol. XXIII [1912], pp. 93-124; see 

 pp. 112-18; also: "A Geographical Pilgrimage from Ireland to Italy," Ann. Assoc. 

 Amer. Geogrs., II [1913], pp. 73-100; see pp. 89-92.) will share a similar fate, or whether 

 it wUl be adopted Uke monadnock remains to be seen. 



