F. GEOGRArilY. 257 



and deep, narrow caiions with vertical walls, both present- 

 ing well-nigh impassable barriers to travel. The only con- 

 siderable bodies of irrigable lands found are along the valleys 

 of the Green and San Rafael Rivers. The only timber lands 

 are on the Sevier plateau, at an elevation of from 8000 to 

 11,500 feet. 



Tiie work of topographic party No. 2, under Mr. Ren- 

 shaw, was confined to Southwestern Utah and Southeast- 

 ern Nevada, one of the most ruo'oed and barren sections in 

 the Great Basin. The methods of survev were the same as 

 those adopted by party No. 1, except that j^erspective profile 

 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. Renshaw and his 

 able assistant, Mr. O. D. Wheeler, was extended over about 

 4000 square miles. In all this area no considerable 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 four miles to 

 the inch ; but this being thought too small a scale to admit 

 of correct representation of the details of the geology. 

 Professor Gilbert, in addition to his geological work, made 

 a more detailed survey of the topography, carrying a com- 

 plete system of secondary triangulation, and a connected 

 plane-table sketch, over more than 1000 square miles. The 

 data collected are sufficient to make a topographic map of 

 the Henry Mountains on the scale of two miles to the inch, 



^^ 6 3 0* 



The Rocky Mountain region of the United States (not in- 

 cluding Alaska), or tliat portion west of the meridian of 99 

 30', was by a former Secretary of the Interior divided into 

 districts for surveying and mapping purposes, and these dis- 

 tricts numbered; the area of each district is 2^ in longitude, 

 1 ^ in latitude. The region of country surveyed by the parties 

 under the direction of Professor Powell is embraced in dis- 

 tricts numbered 75, 85, 86, 95, 96, 104, and 105, tlie first five 

 lying directly west of the region in which Dr. Hayden is en- 

 gaged, while districts 104 and 105 lie immediately soutli of 

 the other districts in which lie himself has been at work. 

 During the earlier part of his work, before these districts 



