46 GEOLOGY OF THE HIGH PLATEAUS. 



These traces are less conspicuous on the eastern terraces than upon the 

 southern, but are seldom absent. In the Great Basin west of the plateaus 

 there is no evidence of any such general uplifting in the later periods, at 

 least within many leagues of the High Plateaus, although local disturb- 

 ances of no small magnitude have occurred, and doubtless the southwestern 

 ranges have gained notably in altitude. 



It is interesting to compare the structural forms produced by the 

 displacements of the High Plateaus and Kaibabs with those observed in 

 other countries and in other parts of the Pocky Mountain Region. The 

 earliest ideas acquired by geologists concerning mountain structure were 

 derived from the study of the Alps and Jura The conspicuous fact 

 there presented is plication — waves of strata like the billows of the ocean 

 rolling into shallow waters, and often a more extreme flexing until the folds 

 become closely appressed. With the extension of observation among the 

 other mountain belts of Europe, and wherever the traces of great disturb- 

 ance among the strata were found, the same phenomenon of repetitive flex- 

 ing was discerned, seldom amounting to " close plication," but undulating 

 in greater or less degree. At a later period, when geology was colonize! 

 in America, its systematic researches were first prosecuted in the Apala- 

 chians, where the same order of facts was presented in a degree of perfec- 

 tion and upon a scale of magnitude far surpassing - the original types of 

 Switzerland. At a still later period the geologists who inaugurated in the 

 Sierra Nevada and Coast Ranges the study of the Rocky system disclosed 

 another grand example of the same relations. Thus the increase of obser- 

 vation has been for man}- years strengthening the original induction that 

 plication and mountain-building are correlative terms. 



But the rapid and energetic surveys of the remaining portions of the 

 Rocky Mountain Region have within a few years brought to light facts of a 

 different order. From the eastern base of the Sierra Nevada to the Great 

 Plains are very many mountain ranges, a large proportion of which have come 

 under the scrutiny of geologists; and of those which have been hitherto 

 studied sufficiently to justify any conclusions concerning their structure 

 not one has been found to be plicated. Not one of them presents any 

 recognizable analogy to the structure which is so remarkably typified in 



