PHYSICAL FEATURES OF COLORADO VALLEY. 393 



gram. Let the lines II, H-H, 77", represent the limit of the contin- 

 uation of these beds. In the shaft 6^ these beds also are exposed 

 above those seen in shaft F. 



The altitude of the rocks above the line of observation (vl, B) is 

 exaggerated about five times. If they were reduced to one-fifth, the 

 proportion between the rocks seen in the various escarpments of these 

 mountains, and those carried away below the broken lines, would be 

 projjerly represented. 



Fig. 4. a Cataclinal Vallet 



By sinking a shaft, only a little surface along the edge of the strata 

 could be seen ; but on the sides of the fold they are exposed for many 

 miles, and often the top or bottom is cleared off for a great space, 

 revealing even the ripple-marks of the ancient sea, or rounded impres- 

 sions of rain-drops which fell in that elder time ; or the sands have 

 buried shells and bones of ancient animals, and they are still encased 

 in the rock ; and even impressions of leaves that were buried in the 

 mud can yet be seen in such a fine state of preservation that you can 

 trace their delicate veins. 



In speaking of the great upheaval of rocks from which the Uinta 

 ^Mountains are carved, I have spoken of wrinkling and folding, as if 

 the rocks sstqyq always flexed ; but these displacements are sometimes 

 attended with fractures, on one side of which the rocks are upheaved, 

 or thrown down on the other. Such displacements are called faults. 

 Faults like these are seen in many places in the Uinta Mountains ; one 

 great one, on the north side, the throw of which is nearly 20,000 feet, 

 and many others are found of lesser magnitude. 



In speaking of elevation and depression by faulting or folding, it 

 must be understood that reference is made to a change of altitude in 



