LETTER TO THE SECRETARY 



Washington, D. C, March 10, 1873. 



Sir : I have the honor to present for your approval and for publica- 

 tion the sixth annual report of the United States Geological Survey of 

 the Territories, containing a iireliminary account of explorations made 

 during the summer of '1872, about the sources of Snake and Missouri 

 Elvers. 



The liberal appropriation granted for the survey by the Forty- 

 second Congress enabled the Chief Geologist to organize two large and 

 well-equipped parties for tield-work. These parties were each provided 

 with a geologist, topographer, astronomer, meteorologist, with their as- 

 sistants. A number of young men acted as collectors of objects in 

 natural history. 



One party, under my immediate direction, took Fort Ellis as its ini- 

 tial i^oint. We spent several days at this point and at Bozeman pur- 

 chasing our animals and securing supplies and other outfit. After our 

 preparations were made, we passed over the divide to the Yellowstone 

 A^alley, traversing nearly the same route as last year. The Yellowstone 

 Eiver, from the lower canon to its source in the Yellowstone Lake, was 

 carefully surveyed. Some of the branches, as the East Fork, were more 

 fully examined than at any time previously. From the lake the party 

 passed over the divide into the Geyser Basin of Madison Eiver, and ex- 

 plored that river and its branches to the Three Forks. We then 

 ascended the Gallatin Eiver and examined it to its sources. The inter- 

 esting canon of the Gallatin, which is about seventy miles in length, 

 had never been explored previously, and was unknown even to the in- 

 habitants of the lower part of the valley. From the Gallatin Canon we 

 passed over the divide into the Y^ellowstone Valley, near the second 

 caiioB, and made a more detailed survey of the Snowy or Yellowstone 

 Eange, then passed down the valley through the first or lower canon, 

 and then along the divide between the branches of the East Gallatin 

 and Shields Elvers to Flat Head Pass ; thence across the rugged hills 

 to a point about ten miles below the Three Forks, on the Missouri Eiver. 

 We then returned to Bozeman along the base'of the mountains on the 

 east side of the East Gallatin Fork, and the field-work of this party 

 was closed. The materials for an accurate map of the district examined 

 were secured, and most important discoveries in geology and large col- 

 lections in all departments were made. 



The second party was placed under the general direction of Mr. James 



