REPORT OF THE SECRETARY. 85 



beeu made from time to time upon the geysers enabled Mr. Hague to 

 institute a more sj'stematic study of tbe changes and modifications. 

 Skilled observers were kept in the principal geyser basins, and as far as 

 possible the more remote and less active thermal springs were visited 

 and the phenomena connected therewith carefully noted. Two j^arties, 

 one of which was under Mr. Hague's immediate direction, made a pre- 

 liminary study of the East Gallatin Range, which forms the northwest 

 boundary of the Park Plateau, and extends from Electric Peak south- 

 ward to Mount Holmes. Geologically considered, this range is a most 

 interesting one; every i^eriod from the Silurian to the Colorado Creta- 

 ceous being represented therein. A special study was made of the 

 Obsidian cliffs, and later in the season the volcanic rocks of the west 

 shore of the Yellowstone Lake, together with its Quaternary geology, 

 glacial i)henomena, and ancient terrace-lines, were carefully worked up. 



In connection with the geologic investigations, Mr. Hague also made 

 a preliminary examination of the region named in the bill before the 

 Forty-eighth Congress for addition to the Park reservation. 



The several parties were compelled by reason of snow-storms to leave 

 the Park by the middle of October. Upon returning east the ibrce of 

 this division were removed from their quarters in the American Museum 

 of Natural History, in New York, to the Survey building, in Washing- 

 ton. 



Colorado District. — During the winter Mr. S. F, Emmons and assist- 

 ants made further study of the material collected from the Silver Cliff 

 mining district, and, as soon as the field, season opened, topographic 

 and geologic work was taken up in the Gunnison district. In connec- 

 tion therewith, and in order that a better understanding mig])t be ob- 

 tained of the Colorado Paleozoic and Mesozoic, a geologic section was 

 made along the Arkansas River, in the neighborhood of Salida. The 

 result of the season's work will enable the geologists to lay down the 

 geology of the Gunnison district upon the map of the region which 

 was prepared at the same time. As soon as the weather made further 

 research in these fields impossible, attention was turned to the geologic 

 phenomena of the Denver Basin, especial attention being given to the 

 source of the water-supply of its artesian wells. The investigations in 

 this region, dealing as they do with the mineral-bearing formations, 

 require a large amount of laboratory and microscopic work, in the course 

 of which some very interesting discoveries were -made as to the occur- 

 rence of minerals both in combinations and in localities in which they 

 were not supposed to exist. Tho results of these investigations of the 

 minerals of Colorado will appear at a future day in the form of a Bulletin. 



District of the Pacific. — At the close of the previous annual state- 

 ment, the investigations of Mr. George F. Becker and his assistants in 

 the quicksilver deposits of Sulphur Bank and New Idria, California, 

 were sufficiently near completion to permit the entering upon new 

 fields. It was decided, therefore, to take up the study of the Knoxville 



