258 
THE GEAND CASfON DISTEICT. 
readily explained. The Kaibab is now, and throughout the period of evo- 
lution of the chasm it always has been, higher than the other plateaus. 
Corrasion has, therefore, penetrated there more deeply than elsewhere. It 
has, moreover, laid bare the edges of the softer beds underlying the Red 
Wall, and the rapid decay of these lower beds has undermined and wasted 
the Red Wall to a great extent In the other divisions of the chasm con’a- 
sion has only at a very recent period cut below this great series of hard 
limestones. In a word, the process of development of the canon is much 
more advanced than elsewhere. Besides the greater altitude leading to 
deeper corrasion, the climate of the Kaibab is moister, and the degrading 
forces are, therefore, more efScient. If, in future periods, the three western 
plateaus should be further elevated, it may be anticipated that the chasm 
would there assume gradually the features now seen in the Kaibab. 
There are certain forms in the contours or ground plans of cliffs which 
claim attention. One of the most striking features in the vast maze of cliff- 
work in the Glrand Canon is found in the extremely tortuous lines of front- 
age. They wind about in a most intricate manner and rarely extend in 
straight lines through any considerable distances. The lines of trend 
usually are a succession of sweeping curves and sharp angles. The first 
view is extremely confusing, and under the influence of many causes of 
optical delusion prevailing in the landscape, it is very difficult to see any- 
thing but chaos — an utter absence of anything like system or arrangement. 
But patient study and analysis at length reveal many striking evidences of 
order. If we consider any one of the larger amphitheaters opening later- 
ally into the main chasm, we shall note that it has many lateral amphithea- 
ters opening into it of an inferior order of magnitude. This is well por- 
trayed in Mr. Bodfish’s map of the Kaibab division. All of them are the 
result of corrasion and weathering. They illustrate the remarkable uni- 
formity of the rate of weathering. The upper ends of the minor recesses 
are usually rounded in contour. The longitudinal wall extending to its 
confluence with the main amphitheater makes at that point a sharp angle. 
The weathering of these walls has obviously originated in the corrading 
channels of the lateral tributaries and their minuter branches. As the nar- 
row cleft cut by the sinking stream deepened it also widened. If we rep- 
