Gregory — Progress in Interpretation of Land Forms. 109 



and the height consequently is less." Speaking of the 

 magnificent stream-cut canyons of the Blue Mountains 

 of New South Wales, gorges which lead to narrow exits 

 through monoclines, Darwin says: "To attribute these 

 hollows to alluvial action would be preposterous." 11 



The influence of structure in the formation of valleys 

 is emphasized by many contributors' to the Journal. 

 Hildreth in 1836, in a valuable paper, 12 which is perhaps 

 the first detailed topographic description of drainage in 

 folded strata, expresses the opinion that the West Vir- 

 ginia ridges and valleys antedated the streams and that 

 water gaps though cut by rivers involve pre-existing 

 lakes. Geddes (1826) 13 denied that Niagara River cut its 

 channel and speaks of valleys which "were valleys e'er 

 moving spirit bade the waters flow." Conrad (1839) 14 

 discussed the structural control of the Mohawk, the 

 Ohio, and the Mississippi, and Lieutenant Warren 

 (1859) 15 concluded that the Niobrara must have orig- 

 inated in a fissure. According to Lesley (1862) 16 

 the course of the New River across the Great Val- 

 ley and into the Appalachians "striking the escarp- 

 ment in the face" is determined by the junction of 

 anticlinal structures on the north with faulted mono- 

 clines toward the south; a conclusion in harmony 

 with the views of Edward Hitchcock (1841) 17 that major 

 valleys and mountain passes are structural in origin and 

 that even subordinate folds and faults may determine 

 minor features. "Is not this a beautiful example of 

 prospective benevolence on the part of the Deity, thus, 

 by means of a violent fracture of primary moun- 

 tains, to provide for easy intercommunication through 

 alpine regions, countless ages afterwards!" The extent 

 of the wandering from the guidance of DeSaussure and 

 Play fair after the lapse of 50 years is shown by students 

 of Switzerland. Alpine valleys to Murchison (1851) 

 were bays of an ancient sea; Schlaginweit (1852) found 

 regional and local complicated crustal movements a satis- 

 factory cause, and Forbes (1863) saw only glaciers. 



Valleys Formed by Rivers. 



One strong voice before 1860 appears to have called 

 Americans back to truths expounded by Desmarest and 

 Hutton. Dana in 1850 1S amply demonstrated that val- 

 levs on the Pacific Islands owe neither their origin, 



