THE CANONS OF THE COLORADO. 53 



sand, and boulders, the last of which, indeed, while wearing 

 the bed of the river, are still more worn themselves, being 

 finally reduced to mud, which is more or less dissolved 

 before reaching its journey's end. But the sand is the most 

 important tool, and the river has used it to such purpose 

 that it has cut the rock into deep gorges or canons (Fig. 13), 

 which extend throughout more than 1,000 miles of its course, 

 and are from 600 feet to more than a mile deep, though in 

 some parts only twenty or thirty feet wide. The great 

 river, when viewed from above, dwindles to a silver thread 

 at the bottom of these gloomy sunless gorges, through whose 

 long length no one in these days is known to have passed 

 alive except the members of the exploring expeditions sent 

 out in 1869 and 1872, though horrible tales are current of the 

 sufferings of those who, having once taken refuge within 

 them, have found escape well-nigh impossible. In addition 

 to the enormous height of the cliffs, there is the further 

 difficulty that they are for the most part undermined, the 

 weathering above being quite unable to keep pace with the 

 rapid working of the river below. The only practicable 

 points of exit, therefore, are at the rare openings made in 

 these giant walls, where the river is joined by its tributaries. 



Each tributary of the Colorado, every branch of each 

 tributary, and each little stream and rill, has cut for itself 

 similar canons on a larger or smaller scale, and hence the 

 whole country is such a perfect labyrinth of chasms, that it 

 is a difficult matter to choose routes for railroads and other 

 traffic. 



In the adjoining state of New Mexico, similar canons, 

 some of them 1,000 feet deep have been cut in the sandstone 



