J 4 GEOLOGY OF TDE BLACK HILLS 



part of Colorado — from Cheyenne and Fort Laramie westward to Fort 

 Bridger and the Soutli Pass. The results of these two years' work were 

 made public in two annual reports issued by the General Land Office.* 



The more complete report of the exploration in Nebraska and the parts 

 of the Territories immediately adjoining-, prepared in 18G8, was published 

 by the Commissioner of the General Land Office in 1872.t 



III tlio following- year, 1869, the ajjpropriation for the surveys under 

 Dr. Hayden's care was increased, and the work was placed under the im- 

 mediate direction of the Secretary of the Interior. The field of operations 

 was transferred to the Territories of Colorado and New ^lexico, and the 

 results of the year's work were published in a rej)ort to the Secretary of the 

 Interior.! In 1870, 1871, and 1872, the field of survey was once more 

 north of the railroad, but it included no portion either of eastern Wyoming 

 or of Dakota. The results were published in annual reports to the Secretaiy 

 of the Interior.§ Since 1872 the field of survey has again been transfen-ed 

 to the Territories lying south of the railroad. 



In 1873 Captain W. A. Jones, United States Engineers, proceeded from 

 Fort Bridger to northwestern Wyoming, and made a reconnaissance of the 

 country within that Territory about the headwaters of the Snake, Big- 

 horn, Grey Bull, Clark's Fork, and Yellowstone Rivers. This expedition 

 was accompanied by Prof. T. B. Comstock as geologist, and though much 

 of the territory examined had already been passed over by Hayden and 

 other explorers, the report of Professor Comstock affords many valuable 

 additions to our knowledge of the geological structure of the Wind River 

 Mountains and the adjoining region, including the headwaters of the Yel- 

 lowstone and the Yellowstone National Park. 11 



• First Annual Report of United States Geological Survey of the Territories, embracing Nebraska. 

 8vo., pp. 64, 18()7, and Second Annual Report, &c., embracing Wyoming. 8vo., pp. 36, 1868. 



t Final Report of the United States Geological Survey of Nebraska and portions of adjacent Ter- 

 ritories. Kvo., \>[t. '269, plates xi, and Geological Map. ' 



t Third Annual Report of United States Geological Survey of Territories, embracing Colorado and 

 New Mexico. 8vo., pp. 'i."}. Washington, 1870. 



ij United States Geological Survey Wyoming and contiguous Territories. 8vo., pp.511. Washing- 

 ton, 1871. United States Geological Survey Montana and adjoining Territories. 8vo., pp. 538. Wash- 

 ington, 1872. United States Geological Survey Montana, Wyoming, &c. 8vo., pp. 844. Washington, 

 1873. 



II Northwestern Wyoming, including Yellowstone National Park, Geology, by Prof. T. B. Corn- 

 stock. 8vo., pp. 331, majJs 51. Washington, 1875. 



