REPOET OF A. C. PEALE, M. D. 



Washington, D. 0. 



Deae Sir : I have the honor to transmit herewith my report for the 

 season of 1872. I have divided it into six chapters. The tirst I have 

 devoted to the description of a short trip into Colorado and Utah, made 

 before the organization of the party was completed. The second chapter 

 contains an account of our progress from Fort Ellis, Monl^ana Territory, 

 to Gardiner's Eiver, in the Yellowstone National Park, including an 

 account of the Hot Springs at the latter place. The third chapter con- 

 tains a description of the springs in the iLcHowstone Valley from Gar- 

 diner's Eiver to Yellowstone Lake. The fourth chapter is devoted to 

 the geyser-basins of Fire-Hole Eiver. 



The time we were in the geyser-basins was somewhat limited, and the 

 observations must therefore be to some extent necessarily incomplete. 

 To work up this most interesting section thoroughly will require the 

 time of at least one entire season, so that data may be obtained as to 

 the influence the different portions of the year may liave upon the 

 geysers. Then, also, more could be definitely learned in regard to their 

 regularity or irregularity. As far as the time permitted, I have endeav- 

 ored to make the observations as complete as possible. 



At this point I wish to express my thanks to Dr. F. M. Endlich, of 

 the Smithsonian, for assistance rendered in analysis. That I am able 

 to present so many analyses, especially of specimens from the geysers, 

 is due largely to his assistance. I wish also to refer to Mr. W. B. Piatt, 

 of the expedition, who also assisted in analysis. 



My fifth and sixth chapters I have devoted to the consideration of the 

 Madison and Gallatin Valleys. Appended to the report are catalogues 

 of the rocks and minerals collected during the summer. I have incor- 

 porated in them the specimens collected by both branches of the expe- 

 dition. I have also done the same in the catalogue of thermal springs, 

 which is appended to the report. In the latter catalogue I have, for the 

 sake of comparison, included observations of some of the springs taken 

 in previous years (principally by Long and by Fremont) wherever there 

 was no doubt as to the localities being the same. 



The collections of geyserite this year are particularly large, and pre- 

 sent all the varieties in form and texture to be found in the region. 



In conclusion I wish to express my thanks to all the members of the 

 expedition for their uniform kindness and co-operation. I would refer 

 particularly to Mr. T. O'C. Sloane, who for a while acted as my assistant, 

 and who, by his zeal and activity, contributed largely to the collections. 



To the editors of the " aSTew York Illustrated Christian Weekly " I am 

 indebted for some of the best wood-cuts illustrating my report. 



Trusting this report may prove satisfactory, I have the honor to be 

 your obedient servant, 



A. C. PEALE. 



Dr. F. V. Hayden, 



United ^States Geologist. 



