

REPORT OF THE SECRETARY. 59 



The work of topographic party No. 2, under Mr. Benshaw, was con- 

 fined to Southwestern Utah and Southeastern Nevada, one of the most 

 rugged and barren sections in the Great Basin. The methods of survey 

 were the same as adopted by party No. 1, except that perspective pro- 

 file sketches were made by the aid of the orograph, a newly designed 

 instrument that promises to be of great use in topographic surveying. 

 The work of Mr. Benshaw and his able assistant, Mr. O. D. Wheeler, 

 was extended over about 4,000 square miles. In all this area no con- 

 siderable bodies of irrigable lands are found ; probably not one-half of 

 one per cent, possessing any value except for pasturage. 



A topographic survey of the Henry Mountains was made in 1875, and 

 a map constructed on a scale of 4 miles to the inch, but this being- 

 thought too small a scale to admit of correct representation of the details 

 of the geology, Mr. Gilbert, in addition to his geological work, made 

 a more detailed survey of the topography, carrying a complete system 

 of secondary triaugulation and a connected plane-table sketch over more 

 than 1,000 square miles. The data collected are sufficient to make a 

 topographic map of the Henry Mountains on the scale of 2 miles to the 

 inch, or 1-63000. 



The Bocky Mountain Begion of the United States, (not including 

 Alaska,) or that portion west of the meridian of 99° 30', was by a for- 

 mer Secretary of the Interior divided into districts for surveying awl 

 mapping purposes, and these districts numbered; the area of each dis- 

 trict is 2£ degrees in longitude, and 1^ degrees in latitude. The region 

 of country surveyed by the parties under the direction of Professor 

 Powell is embraced in districts numbered 75, 85, 86, 95, 96, 104, and 105, 

 the first five lying directly west of the region in which Dr. Haydeu is 

 engaged, while districts 104 and 105 lie immediately south of the other 

 districts in which he himself has been at work. During the earlier part 

 of his work, before these districts were established by the Department, 

 Professor Powell's work extended in an oblique direction from northeast 

 to southwest along the general course of the Green and Colorado Bivers 

 through the districts above designated, but the work was in such condi- 

 tion that no one district was complete. During the present season his 

 parties have been engaged in extending the survey over the unsurveyed 

 fractional districts, so that final and complete maps of each may be con- 

 structed. 



The methods of survey during the present season are essentially the 

 same as those employed during the last, being modified to a slight 

 extent as experience has suggested ; the chief improvements are in the 

 method of triangulation. In addition to the determination of geodetic 

 positions and general geographic features, the system of classifying the 

 lands inaugurated in former years has been continued during the present, 

 the object of this classification being to determine the extent and posi- 

 tion of the irrigable lands, timber lands, grass lands, mineral lands, 

 and waste lauds ; the latter being composed of rugged mountains and 



