REPORT UNITED STATES GEOLOGICAL SURVEY. KV 
eeeded from Point of Rocks Station northward, along the west side of 
the Wind River Mountains, and up the Snake River Valley to the Yel- 
lowstone Park, where he joined the second division. In the mean time 
he was engaged in making sketches, panoramic views, and geological 
sections of the intermediate country, all of which will prove of the 
highest importance in illustrating the geological structure of this most 
interesting and complicated region. 
The latter part of the sammer was spent in making detailed geological 
examinations in the district that includes the National Park. The greater 
portion of the park was found to be covered with somewhat uniform 
flows of the ordinary voleanie rocks. Features of more than ordinary 
geologic interest occur, however, along the northern border of the park 
district. Here a small belt, not more than 15 by 30 miles in extent, con- 
tains a fair epitome of the geology of the Rocky Mountain region. The 
whole series of formations from the earliest to the most recent are almost 
typically developed. The only marked irregularity in the succession of 
geologic events occurred during the great mountain-building period of 
the Middle Tertiary. After that followed a number of inferior oscillations 
of the surface, during which an extensive series of recent Tertiary and 
volcanic rocks were deposited. Connecting this period with the present 
are the deposits of a number of great lakes, which at the present time 
have their chief representative in Yellowstone Lake. Detailed inves- 
tigations were made at many points of interest, and a fine mineralogical 
collectien was made. 
In the mean time Mr. Holmes made sketches covering every square 
mile of the Park, an area of 3,500 square miles. In such minute detail 
was the work done that the economic resources, as well as all the minor 
features of the geology, can be laid down on a map on a scale of one 
mile to an inch with the greatest care and minuteness. The great variety 
of forms which the mountains in and around the park assume can be 
presented to the eye by panoramic views with wonderful distinctness. 
The third division, under Mr. I. A. Clark, surveyed the Wind River 
Mountains, a portion of the Wyoming Range, the Gros Ventre Range, 
with a large area in the Snake River Valley. Mr. Clark made 31 gradi- 
enter stations and 15 compass Stations. The area lies between latitude 
43° and 44° and longitude 109° 15’ and 111°. This includes the upper 
portion of the Wind River Mountains, with portions of the Wyoming 
Kange, the Gros Ventre Range, and portions of the Shoshone Mount- 
ains and the Owl Creek Range; also the sources of Green River, Hoback 
Basin, and upper waters of Wind River. Mr. St. John acted as geolo- 
gist and Mr. N. W. Perry as mineralogist to this party. Their reports 
will prove of general interest. Mines of gold, silver, iron, and vast 
beds of gypsum, as well as many other minerals, were found. 
In the prosecution of the field-work of the Survey during the past 
season a photographie division was again put in operation, after an 
interval of two years, under the leadership of Mr. W. H. Jackson, who 
