72 APPENDIX TO EEPORT OF THE SECRETARY. 



have been determined by their angular relations, and the scenic char- 

 acteristics necessary to give proper effect to the maps have been out- 

 lined by instrumental means. In this manner the subsequent construc- 

 tion of maps at the office, ready for the engraver, is reduced to a 

 minimum of labor, while for the proper accuracy the topographer is not 

 necessitated to resort to his memory for the appearance of the land- 

 scape, but only to the definite record. 



Barometers. — The instruments used in the hypsometric work are Green's 

 mercurial mountain barometers, Green's psychrometers, and aneroid bar- 

 ometers of the usual construction. 



Cartography . — Much attention has been given to this subject for the 

 purpose of determining the best method of representing the topography 

 of the region surveyed, taking into consideration the character of the 

 country, the more important facts to be embodied, and the scale adopted 

 for the physical atlas of the Interior Department. The systems of car- 

 tography in use in this country and many of those of Europe have been 

 examined and studied, and many experiments have been made in the 

 office for the purpose of determining the best methods adapted to these 

 circumstances and conditions. 



For the physical atlas heretofore mentioned it is proposed to represent 

 the topography by contour lines with auxiliary hatchings to indicate 

 rock surface and shading for general reliefs, these so applied as not to 

 obscure the contours. For special purposes hatched maps are used, for 

 others contour maps, and for purposes relating to the discussion of geo- 

 logical structure maps are made by photographing or lithographing 

 models or relief maps in plaster. 



Classification of lands hy Mr. Gilbert. — The survey under the direction 

 of Professor Powell has been extended over the northern portion of 

 Arizona and the greater part of Utah, but a broad strip along the north- 

 ern end of the latter Territory was embraced in the survey made by Mr. 

 Clarence King, under the War Department. It seemed desirable, how- 

 ever, to extend the classification of lands over this latter region, and 

 this duty was assigned to Mr. G. K. Gilbert. 



Mr. Gilbert took the field at Salt Lake City and traversed all of the 

 Territory lying west, north, and northeast of that point, a tract compri- 

 sing so much of the drainage basin of Great Salt Lake as lies in Utah. In 

 this area is included the most valuable portion of the Territory, as well 

 as the most sterile. A very small part of it will repay cultivation 

 without irrigation, but this is exceptional, and in general the possibility 

 of agriculture depends upon the possibility of artificial watering. The 

 Bear Eiver, the Weber, and the Jordan carry as much water as can 

 profitably be used upon all the lands to which it is practicable to convey 

 them by canals, and those lands were measured, in order to determine 

 the agricultural capacities of the river valleys. The smaller streams, on 

 the contrary, are inadequate to serve the arable lands through which 

 they severally run, and the agricultural capacities of their valleys were as- 



