I REPOET UNITED STATES GEOLOGICAL SURVEY. 



In order that tbose wlio follow me may be able to utilize the many 

 facts already gathered, 1 have indicated in most cases the routes fol- 

 lowed, and pointed out the exact localities at which observations were 

 made. In arranging my report I have taken up a number of the more 

 important localities as topics, and treated each one as fully as possible 

 before passing on to the next. The order of succession is pretty nearly 

 such as would naturally be adopted by the observer who approaches 

 l!he Park from the north by way of the Yellowstone Valley. 



To discuss the geologic formations in the order of their age would in- 

 volve too much skipping about for convenient reference, besides such 

 treatment is not suited to the presentation of fragmentary data. 



A large collection of hand specimens of the igneous rocks of the 

 Park was made, and about 30 specimens have been submitted to Capt. 

 C E. Button for microscopic examination. I wish here to express my 

 obligations to him for the report which he has kindly furnished, as well 

 as for valuable assistance in the study of the general lithologic charac- 

 ters of the collection. 



I am under obligations to Dr. A. C. Peale for observations made in 

 the southwest corner of the Park before my arrival, as well as for other 

 notes on the geology of such localities as his study of the hot springs 

 eniabled him to visit. 



I am also under obligations to Mr. Henry Gannett, director of the 

 party, for the most generous co-oj)eration and assistance. 



XAMEATI FE. 



Shortly before leaving Washington it was definitely arranged that I 

 should join Mr. Gannett's party, and carry on the geologic work of the 

 Park Division, Dr. A. C. Peale, the regular geologist of that division, 

 having been assigned to the duty of making a detailed survey of the 

 thermal springs of that region. In order, however, that I might have 

 the opportunity of visiting the Wind Eiver and Teton Mountains for 

 the purpose of making panoramic views, I was permitted to join the 

 primary triangulation party, under Mr. Wilson, at Point of Eocks, Wyo- 

 ming, and remain with it until we should reach the east base of the 

 Teton Eange. 



From the summits of Wind Eiver and Fremont's Peaks I obtained 

 good views of the superb range to which they belong, and besides this 

 made many sketches amongst the remarkable glacial regions of the 

 western slope. ^ 



Having reached the Snake Eiver Valley, Mr. Wilson was compelled 

 to cross the Teton Eange, for the x)urpose of ascending the Grand Teton 

 from the west ; I therefore joined the photographic party under the di- 

 xection of Mr. W. H. Jacksou, and accompanied him up the broad val- 

 ley of the Snake to the base of the Upper Gros Ventre Butte. From 

 both Upper and Lower Gros Ventre Buttes I made sketches of the 

 magnificent range to the west. The hazy condition of the atmosphere 

 rendered sketching difficult and photography almost impossible, but 

 imparted to the mountains themselves additional grandeur and assisted 

 in confirming our previous impression that this range is the finest in 

 the Eocky Mountains. 



Taking leave of Mr. Jackson's party at the base of the Grand Teton, 

 I made all haste to join Mr. Gannett's party in the Yellowstone Park. 



