288 S. V. EMMONS UINTA MOUNTAINS , 



width. The interior of the ellipse has a general level of about 10,000 

 feet, out of which rise sharj^, narrow ridges and peaks of horizontally 

 bedded quartzites to elevations of 12,000 and 13,000 feet. The plateau- 

 like surface between the peaks consists of a series of shallow, glacial 

 basins, well clothed with pine forest and studded with innumerable glacial 

 tarns. The streams that drain these basins run in a series of rapidly 

 deepening canyons with nearly vertical walls that reach depths of 3,000 

 to 4,000 feet before they emerge into the open plain country on either 

 flank. On the broad, flat spurs between these canyons gently sloping 

 Tertiary beds lap over the upturned Mesozoic and Paleozoic to elevations 

 attaining in some places 10,000 feet, which, together with the abundant 

 accumulations of moraine material, effectually mask much of the under 

 geology, especially on the northern flank. This general description ap- 

 plies more particularly to the western two-thirds of the range. Toward 

 the eastern end the general elevation of the interior decreases, the higher 

 peaks reaching elevations of only 8,000 to 9,000 feet, while the mountain 

 mass widens very considerably and the structure becomes correspondiugiy 

 complicated. The single anticlinal fold becomes double, while at the 

 eastern extremity, before the older rocks disappear entirely under the 

 Tertiary beds, the axes of folding take a more nonth and south direction 

 and the uplift ends in two isolated anticlinal billows that raise their crest 

 a little above the sea of horizontal Tertiary beds that now surrounds, but 

 once covered, a great part of the present mountain mass. 



The central core of this mountain mass consists of a series of quartzite 

 beds, over 12,000 feet in thickness, whose age lias long been in doubt. 

 On three published geological majjs they have been assigned successively 

 to as many difl;'erent periods — on the Fortieth Parallel maps to the Car- 

 boniferous, on the Powell map to the Devonian, and on tlie Hayden maps 

 to the Silurian — M^hereas in point of fact they do not belong to any one 

 of the three. 



Purpose of the Paper 



A generation has passed away since these mai)8 were made, during 

 which time the advance in geological knowledge of the West has been so 

 great and the change in methods of work so radical that it is difficult for 

 the younger generation of geologists to appreciate the conditions under 

 which geological work was tlien done. It is my purpose in this article 

 to explain first how it came about that such conflicting statements were 

 made, incidentally pointing out the difference in conditions and methods 

 of work between that time and the preseiit day, and finally, as a result of 

 a reconnaissance during the past summer, to give my conclusions as to. 



