260 
THE GRAND CANON DISTRICT. 
only slightly so. There are literally hundreds of these niches along the 
extent of the limestone front, and, so far as known, they are seen in no 
other member. Mr. Holmes has made a drawing of three of these (Plate 
XLI), which well represents their character. I am unable to explain the 
cause of this persistent phenomenon and am very much perplexed by it. 
There is seldom any long stretch of the Red Wall exposure in which these 
panels are not found, and they are usually of the same form and dimensions 
thi’oughout the Kaibab division. In the Kanab and Uinkaret divisions 
they ai’e much less numerous, though still common. 
The analysis of details in the sculpture of the Grand Canon might be 
extended almost without limit, but the examples here given must suffice. It 
appears that the laws which govern the action of the eroding agents are 
highly complex, though by careful study and close attention they may be 
mastered. As already remarked these peculiar forms would hardly be pos- 
sible in any other region, since no other region (so far as known to me) 
presents similar conditions. These conditions have been stated to be as 
follows, and the effect of each has been stated : (1.) The great elevation 
of the region. (2.) The horizontality of the strata. (3.) A series of strata 
containing very massive beds, which differ greatly among themselves in re- 
spect to obduracy to weathering, but each member being ver}”- homogeneous 
in all its horizontal extent ; in a word, heterogeneity in vertical range and 
homogeneity in horizontal range. (4 ) An arid climate. 
No doubt the question will often be asked, how long has been the time 
occupied in the excavation of the Grand Canon? Unfortunately there is 
no mystery more inscrutable than the duration of geological time. On this 
point geologists have obtained no satisfactory results in any part of the 
v/orld. Whatever periods may have been assigned to the antiquity of past 
events have been assigned provisionally only, and the inferences are almost 
purely hypothetical. In the Plateau Country Nature has, in some respects, 
been more communicative than in other regions, and has answered many 
questions far more fully and graciously. But here, as elsewhere, whenever 
we interrogate her about time other than relative, her lips are sternly closed, 
and her face becomes as the face of the Sphinx. 
