122 HARRY N. EATON 



on the limbs of close folds the topography finds expression in the 

 close association of two ridges of different heights, usually with 

 an intervening lowland on the soft Juniata formation. The dis- 

 crepancy in height is not universal, as in several places in the Belle- 

 fonte quadrangle the Oswego ridges equal and even exceed in 

 height those of the Tuscarora. It is the purpose of this article 

 to show that these "subordinate ridges" as Willis^ styles them, are 

 more numerous than hitherto suspected, that their origin and 

 existence have not been explained satisfactorily by physiographers, 

 and that they constitute a menace to the vahdity of the Cretaceous 

 peneplain theory. 



The existence of subordinate ridges is noted by Willis^ as 

 follows : 



The simple monoclinal ridge which has been described is the typical but 

 not the more common form of the Appalachian ranges. They become com- 

 plex by association of parallel ridges. Thus on the inner slopes of Jacks and 

 Stone mountains, about Kishicoquillas valley, there is a very marked bench or 

 terrace, which appears as a broad step in the mountain slope. In other local- 

 ities, when the outer edge of such a terrace is higher than its surface nearer 

 the mountain, there are narrow ravines separating the terrace edge as a low 

 ridge more or less distinct from the mountain itself. .... Elsewhere, again, 

 .... the subordinate ridge may stand at a level equal with the continuous 

 crest, and it then appears as a distinct monoclinal ridge. 



The Stone Mountain referred to is the southernmost of the series 

 of great consecutive ridges known as the Seven Mountains, which 

 bound the Nittany valley on the south and is immediately north of 

 the Kishicoquillas valley. 



Davis^ recognizes the existence of subordinate ridges: 



The beds of intermediate resistance, the Oriskany and Chemung sand- 

 stones, had not been worn down to baselevel at the close of the Tertiary cycle; 

 they had indeed lost much of the height that they possessed at the close of the 

 previous cycle, but they had not been reduced as low as the softer beds on 

 either side. They were only reduced to ridges of moderate and unequal 

 height over the general plain of the Siluro-Devonian low country, without 

 great strength or rehef but quite strong enough to call for obedience from the 

 streams along side of them. 



' Willis, op. cit., p. 182. ^ Ibid., p. 182. 



3 W. M. Davis, "The Rivers and Valleys of Pennsylvania," Nat. Geog. Mag., I, 

 No. 3 (1889), pp. 243-44. 



