1922] EDWARDS, GEOLOGICAL WORK AT GRAND CANYON 97 



are less resistant, and for the most part form a gentle slope with some 

 steep rises which, however, can be crossed in many places. 



At the head ,of Hermit Trail there has been constructed a rest room 

 known as Hermit's Rest, and to the west of this building the trail 

 plunges over the rim of the canyon. Like all the other trails, it is very 

 winding and it takes many miles of travel to go a short air line distance. 

 The limestone at the top of the canyon is the same as that which forms 

 the great plateaus on both rims, and has been removed, in part, over 

 this entire region in the same way that lower formations have been 

 removed from the lower part of the canyon. This is highly resistant 

 and forms a succession of shelving rock layers, six to ten feet in height, 

 with gentle slopes of about the same thickness separating them. A little 

 farther down, after seven hundred feet of this rock have been crossed, 

 one enters on the part of the trail known as "The White Zigzags," which 

 leads past and over the Coconino sandstone, a white rock that weathers 

 into a vertical wall. These zigzags lead downward for about three 

 hundred feet, until the base of this formation is reached, and at that 

 point the end of the white rock is passed and one enters the red forma- 

 tions which make up the bulk of the canyon wall. The upper part of 

 these red rocks is known as the Supai Formation, and forms a great 

 series of terrace-like steps of red sandstone and shale. These together 

 are over eleven hundred feet in thickness. The steps are caused by the 

 projection of the harder layers of sandstone. The journey across these 

 layers is a long round-about route, with steep places and long gentle 

 slopes. At one point a series of sandstone beds makes a serious ob- 

 stacle and across this the "Red Zigzags" lead down to a second and 

 lower platform. Here at Santa Maria Springs the parties are accus- 

 tomed to stop for lunch and to rest before beginning the further de- 

 scent of the canyon. 



As one reaches the base of the Supai Formation, he comes out upon 

 the top of a very prominent butte which projects from the walls of the 

 canyon far out into the interior. This is known as Point Lookout, and 

 can be seen above Hermit Camp in figure 54. 



Point Lookout is supported by the great mass of limestone which 

 underlies it, and which is called the Redwall Limestone. It is a forma- 

 tion five hundred and fifty feet in thickness which is really of a grayish 

 color, but has been colored red throughout all its exposed parts by the 

 wash from the red shale above it. Throughout most of the course of 

 the canyon this limestone forms an impassable obstacle, btit at the east 

 side of Lookout Point a very rough path with many zigzags leads down 



