REPORT OF FRANK H. BRADLEY, GEOLOGIST. 



Washington, D. C, April 5, 1873. 



Sir : I hand you herewith my report upon the region examined by me 

 during the past season, while accompanying the Snake Kiver division 

 of your party. 



After working for about a month at Ogden, while our outfitting was 

 being completed, we followed well-marked roads to Fort Hall, Idaho, 

 and thence to Market Lake Station. Here we turned off into the almost 

 unbroken wilderness, and spent some time in examining the Teton Mount- 

 ains, from which region we passed up the valley of Henry's Fork to its 

 head, and crossed by Tyghee Pass to the Upper Madison, which we also 

 followed to its source, in Madison Lake, after stopping by the way to 

 examine the geysers and hot springs of the Fire- Hole Basins. Thence 

 we crossed the divide to Shoshone Lake, examined all the head-waters 

 of the main Snake River, and descended that stream, via Jackson's Lake 

 and the Grand Caiion, to its emergence into the Great Basin, reaching 

 the latter at a point only a few miles from Fort Hall. 



From Ogden to Fort Hail, we were able to examine but a narrow strip 

 of country ; but, beyond the latter point, frequent side trips enabled us to 

 understand the general features of quite wide areas, though, at several 

 points, we were so much hurried as to neglect certain small spaces, 

 which are now seen to have been essential tot absolute certainty regard- 

 ing the connections of diiierent x)arts of our work. Upon the whole, 

 however, though much yet remains to be done by subsequent explorers 

 in that region, I am satisfied that they will find but few errors in our 

 results. 



I am indebted to Mr. Bechler, our chief topographer, for many distances 

 and bearings, as well as for the very accurate map which he has now 

 nearly completed, and upon which I expect to color the outcrops of the 

 various formations. I am also indebted to Mr. Hering, astronomer and 

 meteorologist, for the determination of most of the levels indicated in 

 this report. Mr. Gannett, of your own party, has also aided me in this 

 matter. As Mr. Nicholson remained at Fort Hall during our absence, 

 taking hourly observations, while previous barometric comparisons of 

 Fort Hall and Ogden had been made by Messrs. Gannett and Hering, 

 I place much reliance on the determinations of elevations throughout 

 the region examined. 



The skillful i)encil of Mr. Holmes has supplied the sketches which 

 accompany this report, the materials being mostly obtained from the 

 photographs of Mr. Jackson, who accompanied us as far as to the Fire- 

 Hole, and from Mr. Bechler's field-notes. 



Mr. Taggart acted as my assistant during most of the trip; and his 

 work was satisfactory. 



I have to thank our surgeon. Dr. Curtis, for information on certain 

 microscopical points, as, well as for much personal kindness. 



Yours, very respectfully, \ 



FRANK H. BRADLEY, 



Chief Assistant Geologists 



Dr. F. V. Hayden, 



Jn charge of the United States Geological Survey of the Territories. 



