DAVIS: THE GRAND CANYON OF THE COLORADO. 171 



and squash (a, p. 96). Even within the crystallines of the Shivwits 

 block, small side streams of " gentle slope " are reported by Wheeler as 

 entering the main river and forming boulder rapids, but no mention is 

 made of falls at the stream mouths (pp. 166, 167). Plate XVII. , in 

 Button's Monograph, reproduced from a photograph, shows two side 

 canyons entering the narrow inner gorge of the main canyon just east 

 of the Toroweap, and joining the main river in accordant fashion. Evi- 

 dently, then, hanging valleys have no important place in the Grand 

 canyon ; and the hanging lateral valleys of the Alps, whose floors are 

 five hundred feet or more above the open flood plains of their main 

 valleys cannot be explained by normal river erosion. 



Some striking examples of hanging valleys in a very narrow canyon 

 are, however, described by Gilbert in the case of the North fork of 

 Virgin river in southern Utah, where it cuts through the massive 

 Triassic sandstones. This narrow defile is many times deeper than 

 broad ; its walls are nearly vertical and parallel for the greater part 

 of their height, but they depart sufficiently from the vertical, now to 

 this side, now to that, to hide the sky from the adventurous observer 

 who follows the narrow, boulder-strewn stream bed. " The side canons 

 all partake of the chai*acter of the main, but, being worn by smaller 

 streams, are narrower, and their bottoms are of steeper grade. Many of 

 them at their mouths are not cut so deep as the one we followed, and 

 discharge at various heights above the river" (a, p. 79). Gilbert's 

 figure of this canyon has become well known from being copied on the 

 binding'Of Leconte's " Elements of Geology," as if in witness of the effi- 

 ciency of erosive processes ; but it may be noted that a plain of denu- 

 dation, truncating the edges of upturned strata, is a much more impressive 

 though less outspoken witness to this conclusion. 



The Geological Section in the Canton Wall. — The excavation 

 of the Grand canyon is properly regarded as a colossal work. Standing 

 on the southern rim, the view of the chasm is overwhelming; yet the 

 prospect includes four other records of erosion, and suggests two more 

 still, in comparison with any one of which the excavation of the canyon 

 is but a small matter. This has all been pointed out by Powell and 

 others ; but it deserves repeated statement. 



The geological section exposed in the northern side of the canyon in 

 the Kaibab, as seen from any of the promontories in the neighborhood of 

 Cameron and Berry's or Hance's hotels, includes the fundamental crystal- 

 lines, the inclined strata of the Grand canyon series (Algonkian), twelve 

 thousand feet thick, and the palseozoic series, over four thousand feet thick. 



