12 GEOLOGY OF THE BLACK HILLS. 



been proved by our more detailed survey to exhibit unusual accuracy, and 

 it remains a most gratifying testimony to the care and precision of the 

 mapping of Lieutenant Warren, All the subsequent maps of the region, 

 up to the present time, have been based on his work. 



In the year 1859 an expedition under the command of Captain (now 

 Colonel) AV. F. Raynolds, United States Engineers, was organized "for the ex- 

 ploration of the region of country tlu'ough which flow the principal tributaries 

 of the Yellowstone River, and of the mountains in which they and the Galla- 

 tin and Madison forks of the Missouri have their sources." This expedition 

 was accompanied by Dr. Hayden as geologist, and started from Fort Pierre, 

 on the Missouri, en route for Fort Sarpy, on the Yellowstone. Passing by 

 Bear Butte it followed the Red Water Valley westward, and then striking 

 northwest crossed the Belle Fourche branch of the Cheyenne near its great 

 northern bend. A passing examination was made of that portion only of the 

 Black Hills through which their route lay, and a successful scout was made 

 by Mr. J. D. Hutton, topographer, to the curious peak of the Bear Lodge. 

 The rest of the season was spent in explorations of the Bighorn and Pow- 

 der River region, winter quarters being made on the North Platte near Deer 

 Creek. The following year was occupied by different parties of the expe- 

 dition in the exploration of the Wind River, Upper Yellowstone, and Upper 

 Missouri regions, and meeting at Fort Union, at the mouth of the Yellow- 

 stone, the main party followed the Missouri to Fort Randall and Omaha on 

 land, while a division under Lieutenant Maynadier descended the river in 

 boats The preparation of the reports of the expedition was delayed by 

 the war of the rebellion, but a report by General Raynolds was issued in 

 1868,* while the report of Dr. Hayden on the geology of the region visited 

 was published in the following year.f 



In the interval between the making of this survey and the publication 

 of the final official reports there appeared numerous valuable publications 

 on the geology and natural history of the region. In 1857 Dr. Hayden pre- 

 sented the first map of the geology of the region, in a paper read before the 



* Report on theExploratioD of the Yellowstone River, by Bvt. Brig. Gen. W. F. Raynolds. 8vo., 

 pp. 174, with map. Washington, 18G8. 



t Geological Report of the Exploration of the Yellowstone and Missouri rivers, by Dr. F. V. 

 Haydeu. 8vo., pp. 144, with geological map. WasbingtoD, 1869. 



