VIEWS OF AMERICAN WRITERS. 389 



Keyes ^ and Hershey t have recently described the upland of the Ozark 

 plateau in Missouri as an uplifted and dissected peneplain. The region 

 has an essentially horizontal structure, like the Allegheny plateau, with 

 which it is in many ways homologous. The latter author tells of residual 

 hills or monadnocks which still surmount the upland plain, and of faint 

 inequalities of form that seem to mark " the hydrographic basins of the 

 streams which flowed on the Cretaceous lowland plain ; " but as a whole 

 the region was " a low, marshy plain of very slight relief, probably nearly 

 at sealevel." 



Darton describes the Piedmont area of Virginia as — 



' 'An undulating plateau carved in greater part in crystalline rocks . . traversed 

 by rivers which flow in gorges. . . It is now very clearly recognized that the 

 Piedmont plateau is a peneplain of Tertiary age. . . There is a system of very 

 low, flat divides coincident wdth those of the present drainage system." J 



Keith also describes the formerly even surface of the Piedmont belt in 

 which the valleys of today are incised, as a Tertiary baselevel of subae- 

 rial origin. § 



The bevelled western slope of the Sierra Nevada, regarded as an up- 

 turned plain of marine abrasion by Richthofen, is ascribed by Gilbert, || 

 Leconte,^ Lindgren,** Dillerft ^^^ others to subaerial denudation- 

 but Lindgren makes it clear that when the region stood lower it was 

 not worn smooth enough to be called a peneplain; "the declivities and 

 irregularities of the old surface are too considerable for that." 



Diller describes a 2)eneplain formed on the upturned Cretaceous rocks 

 of northern California and now dissected by various streams : 



"The production of such a broad, uniform plain by the erosion of rocks varying 

 greatly in hardness could only be accomplished on a very gentle slope near the 

 level of the controlling water body, and we may therefore properly consider this 

 plain a baselevel of erosion." J J 



Lawson presents an instructive account of an uplifted and dissected 

 peneplain beveled across U[)turned strata in northern California. Water- 

 worn gravels occur on the ridges of the dissected upland. They " can 

 only be interpreted as remnants of the stream gravels of the ancient 

 peneplain." §§ 



*Geol. Surv. Missouri, vol. viii, 1894, pp. 330, 352. 



t American Geolojjjist, vol. xvi, 1895, p. 338. 



X Chicago Jour. Geology, 1894, vol. ii, pp. 568-570. 



§ Fourteenth Ann. Rept. U. S. Geol. Survey, 1894, p. 369. 



II Science, vol. i, 1883, p. 195. 



If Bull. Geol. Soc. Am., vol. 2, 1891, p. 327. 



** Ibid., vol. 4, 1893, p. 298. 



tt Chicago Jour. Geol., vol. ii, 1894, p. 34. 



tl Fourteenth Ann. Rept. U. S. Geol. Survey, 1894, p. 405. 



§g University of California; Bull. Dept. Geol., vol. i, 1894, p. 244. 



