94 GRAND CANON DISTRICT. 



color, which is to be interpreted as meaning an arbitrary subdivision of 

 the Trias. 



The Permian beds consist of sandy clay-shales in very many thin beds 

 and a few thin beds of impure limestone. They are very striking on 

 account of their dense, rich colors, which are sometimes also wonderfully 

 delicate. They are belted in a surprising way. Horizontal streaks of 

 chocolate, purple and red-brown are interstratified with violet, lavender, 

 and white. Perhaps the richest tone is the red-brown, which is almost 

 exactly like the color of the fumes of nitrous acid. Lower in the series 

 are layers of a very peculiar shade of Indian red, alternating with gray 

 ish white. In the lower Trias and Permian the colors reach their climax. 

 Surely no other region in the world, of which I have any knowledge, can 

 exhibit anything comparable to it. Wonderfully even is the bedding. 

 Thin layers may be traced for miles without showing any variation of 

 thickness, color, or texture. In the escarpments the weathering has 

 etched out the harder layers, leaving a line of shadow in the places of 

 the softer layers, and this greatly emphasizes the stratification and gives 

 it finer detail. 



The Permian series is of considerable magnitude. In the western 

 portion of the district its thickness is greater than elsewhere, reaching, 

 probably, 1,400 feet, and possibly 1,000 feet, while in the vicinity of 

 Kanab it is less than 1,000 feet. It gives rise to terminal cliffs, which 

 in the northern part of the Uinkaret are from 800 to 1,000 feet high, 

 while around Kanab their height seldom exceeds 500 or GOO, and is often 

 less than 300. But what they lack in magnitude they make up in refine 

 ment and beauty of detail and in sumptuous color. It is in the Permian 

 that we find the most remarkable buttes. They arc never large, but their 

 resemblances to human architecture or works of design are often amaz- 

 ing. Very few Permian buttes are found in the Grand Canon district, 

 but further eastward, especially in the neighborhood of the junction of 

 the Grand and Green Rivers, they are innumerable and of such definite- 

 ness that the geologist feels as if he were taxing the credulity of his 

 hearers when he asks them to believe that they are the works of nature 

 alone, and not of some race of Titans. 



At the foot of the Permian cliffs begins the Carboniferous platform of 

 the interior region of the Grand Canon district. It stretches southward 

 without visible bound, an almost featureless plain. It terminates be- 

 yond the San Francisco Mountains in the Aubrey Cliffs. 



