AMEKICAN GEOLOGY SURVEYS UNDER HAYDEN. 593 



He pointed out that the main range of the Rocky Mountains "is 

 really a gigantic anticlinal and all the lower ranges and ridges 

 * * * only monoclinals, descending steplike to the plains on each 

 side of the central axis.' 1 Also that there were two kinds of ranges 

 in the Rocky Mountain system — one with a granitoid nucleus, with 

 long lines of fracture, and in the aggregate possessing a specific trend; 

 the other with a basaltic nucleus, composed of a series of volcanic 

 cones or outbursts of igneous rocks, in many ruses forming saw-like 

 ridges like those of the Sierras. 



He found no evidences of any unconformity between the Cretaceous 

 and lower Tertiary beds and no such changes in the sediments as 

 would account for the sudden and apparently complete destruction of 

 organic life at the close of the Cretaceous period. 



He visited the Salt Lake Valle}^ and examined the terraces and old 

 shore lines of Great Salt Lake, describing the beds as of post-Pliocene 

 or Quaternary age and correlating them with the terraces noted by 

 him above the Wasatch Canyon. He found this series of beds so 

 widely extended and so largely developed in Weber and Salt Lake 

 valleys that he regarded it as worthy of a distinct name, and in con- 

 sequence called it the Salt Lake group. He afterwards (in 1871) 

 limited the name to the older beds, which he considered as of later 

 Pliocene age, recognizing the more modern character of the terraces 

 in which he found a great abundance of fresh-water shells. 



The question of priority in this region having arisen between the 

 King and Hayden surveys, it may be well to state that, according to 

 Dr. A. C. Peale, Hayden's first work in the Salt Lake Valley was 

 done in the years 1868, 1869, and 1870, and the results published in 

 February, 1869, during the latter part of 1869, and the early part of 

 1871. The report of the field work of 1870 in Wyoming was first 

 printed in 1871, and a second edition issued in 1872. 



In 1870, with appropriations increased to $25,000, Haydeivs field of 

 operations was transferred to W} T oming and portions of contiguous 

 territories. Stevenson, Elliott, and Thomas were with him as before, 

 while W. H. Jackson, photographer; John H. Beaman, 

 Wyoming a i870. in meteorologist; A. L. Ford, mineralogist; C. P. Car- 

 rington, zoologist, and Henry D. Schmidt, naturalist, 

 were added to the scientific corps. 



The party outfitted at Cheyenne, in Wyoming, and proceeded north- 

 ward along the eastern base of the Laramie range, exploring the Platte 

 River as far as the Red Buttes, and thence passing across the divide to 

 the Sweetwater; thence to the source of the Wind River Mountains, 

 passing down Big and Little Sandy creeks to Green River, and explor- 

 ing the northern slope of the Uinta Mountains. From Fort Bridger 

 the route lay southward to Henrys Fork, which was explored down to 



NAT MUS 1904 38 



