GEOGRAPHICAL REPORT OF HENRY GANNETT, M. E. 



SiE : I have the honor to submit to you herewith my geographical 

 report on the field-work of 1873. 



The party in my charge was composed as follows : Dr. A. 0. Peale, 

 geologist; W. R. Taggart, assistant geologist; Henry W. Sfcuckle, as- 

 sistant topographer, and J. H. Batty, naturalist, with two packers and a 

 cook. 



The party left the depot camp near Denver on May 29, afid spent the 

 following six weeks in the country east and north of South Park. At 

 Fairplay, in the middle of July, we met your party, and together crossed 

 the Arkansas Valley, the Sawatch Range, and the Elk Mountains, work- 

 ing a belt of the country through the middle of the district as far 

 ■west as the one hundred and seventh meridian. After separating from 

 your party on August 10, we finished the southern jjart of the district, 

 then crossed the Elk Mountain divide and finished the northern part, 

 reaching the Arkansas Valley again about the middle of September. 

 The remainder of the season was used in finishing up work which had 

 previously been left partially done, in the country south and east of 

 South Park. 



The plan of the topographical work was as follows : It was all, with 

 slight exceptions, carried on from commanding points, usually the high- 

 est peaks in the neighborhood. A connected system of secondary 

 triaugulation, within the primary system, was carried on with the grad- 

 ienter. In this system all three angles of the triangles were observed 

 whenever possible. The number of stations was 96, and the average 

 distance between them was eight and a half miles. At each station a 

 drainage and a profile sketch were made of the country within the range 

 of vision, and all prominent points were located. Elevations were 

 measured by barometers and dip-angles with the gradienter. The more 

 important streams were meandered. 



The party reached Denver on October 23, and immediately disbanded. 



The notes in the accompanying report concerning the common mam- 

 malia and birds of Colorado were furnished me by Mr. J. H. Batty, nat- 

 uralist of this division. 



The botanical notes, giving a list of the most valuable trees and 

 herbs of the Territory, were given me by Mr. J. M. Coulter, botanist 

 of the survey. 



Very respectfully, yours, 



HENRY GANNETT. 



Dr. F. V. Hayden, 



United States Geologist, in charge United States 



Geological and Geographical Survey of the Territories. 



REPORT. 



The district assigned to the middle division is bounded in latitude by 

 the parallels of 38° 45' and 39° 30', and in longitude by the eighth guide- 



