2 INTRODUCTORY. 



miles If we examine the old War Department maps of the western lialf 

 of the United States and those maps which have been derived from them, 

 we shall find the Wasatch Mountains laid down as extending southward 

 with an increasing westerly trend until the range reaches a point near the 

 southwestern corner of Utah. This delineation conveys to the eye the 

 general truth that along this belt of country there is a lofty and, in a 

 qualified sense, a mountainous barrier separating the drainage system of 

 the Colorado River from that of the Great Basin of the West. It Avould 

 be impracticable upon a map of small scale to designate clearly the fact 

 that the Wasatch as a distinct mountain range ends at Mount Nebo, 75 

 miles south of Great Salt Lake, and that it is here overlapped en echelon 

 by a chain of plateau uplifts which extend southward, gradually swinging 

 around the southeastern rim of the Great Basin. 



These plateaus are not a part, either structurally or topographically, 

 of the Wasatch, but belong to another age, and are totally different 

 in their forms and geological relations. The extension of the name 

 "Wasatch Mountains" south of Nebo is a misnomer. The region south of 

 that mountain has nothing in common with the belt to the north of it, except 

 the mere fact that it carries the boundary line between the two drainage 

 systems; otherwise the two belts constitute one of the most decided of those 

 strong contrasts of topography and geological relations which are some- 

 times presented in adjacent portions of the Rocky Mountain Region. Those 

 who have studied these plateaus have recognized their distinct character, 

 and it seems necessary to give. effect to this recognition to the extent of 

 employing for purposes of geological discussion a distinguishing name. It 

 has seemed to me that for these purposes the belt of country which they 

 occupy would be sufficiently characterized by giving to it the name of tlie 

 District of tiir High Plateaus of Utah 



These uplifts have certain analogies to mountain ranges, but in most 

 cases are distinguished by their well-marked tabular character. 



COMPONENT MEMBERS OP THE GROUPS OF HIGH PLATEAUS. 



There are three ranges of plateaus within the district, and each range 

 can be subdivided into individual tables. The westernmost ranere is made 



