534 THE POPULAR SCIENCE MONTHLY. 



and the foot of Gray Cauon, rocks of Cretaceous and Jurassic Age are 

 found, but they are soft, and have not withstood the action of the 

 water so as to form a caiion. 



These formations differ not only in geological age, but also in 

 structure and color. It will be interesting to notice how these struct- 

 ural differences affect the general contour of the country, and modify 

 its scenic aspects. 



In the description of the three caSons in the history of their explo- 

 ration, the attentive reader has alx'eady noticed the great variety of 

 geological and topographic features observed as we passed along. 



Let us now take a view of the three lines of cliffs. The Brown 

 Cliffs are apparently built of huge blocks of rock, exhibiting plainly 

 the lines of stratification. The beds are usually massive and hard, 

 and break with an angular fracture. The whole is very iricgulai', and 

 set with crags, towers, and pinnacles. The upper beds of the Book 

 Cliffs are somewhat like those last described, and they form a cap to 

 extensive laminated beds of blue shales, in which we see exhibited the 

 curious effects of rain-sculpture. The whole face of the rock is set 

 with buttresses, and these are carved with a fretwork of raised and 

 rounded lines, that extend up and down the face of the rock, and 

 unite below in large ridges. The little valleys between these ridge- 

 lets are the channels of rills that i*oll down the rocks during the 

 storms, and from one stand-point you may look upon millions of these 

 little water-ways. 



Labyrinth Caiion is cut through an homogeneous sandstone. The 

 features of tjie caiion itself have been described, but the cliffs with 

 which it terminates present characteristics peculiar to themselves. 

 Below, we have rounded buttresses, and mounds and hills of sand, 

 and piles of great, angular blocks ; above, the walls are of columnar 

 structure, and sometimes great columns, seen from a distance, appear 

 as if they were elaborately fluted. The brink of this escarpment is a 

 well-defined edge. But if these formations extended over the under- 

 lying beds at one time, and if they have been carried away by rains 

 and rivers, why has not the country between been left comparatively 

 level, or embossed with hills separated by valleys? It is easy to see 

 that a river may cut a channel, and leave its banks steep walls of 

 rocks ; but that rains, which are evenly distributed over a district, 

 should dig it out in great terraces, is not so easy to perceive. 



The climate is exceedingly arid, and the scant vegetation furnishes 

 no protecting covering against the beating storms. But though little 

 rain falls, that which does is employed in erosion to an extent difficult 

 to aj^preciate by one who has only studied the action of water in de- 

 grading the land in a region where grasses, shrubs, and trees, bear the 

 brunt of the storm. A little shower falls, and the water gathers rap- 

 idly into streams, and plunges headlong down the steep slopes, bear- 

 ing with it loads of sand, and for a few minutes, or a few hours, the 



