APPENDIX TO REPORT OF THE SECRETARY. 91 



distinct sheets have been entered. The geological maps are based upon 

 the topographical-atlas sheets, and have corresponding numbers. The 

 following sheets appear with the annual report submitted to the Chief 

 of Engineers, June 30, 1877, viz : Atlas-sheet 53 0, embracing portions 

 of Central Colorado, and showing the drainage-basin of the South Platte 

 Eiver; CI B, Central Colorado, showing portions of the drainage basin 

 of the Eio Grande, Arkansas, Gunnison, and South Platte rivers, indi- 

 cating economic features; Gl C, sub, part of Southwest Colorado, and 

 drainage-basins of the Gunnison, Eio Grande, Animas, Miguel, and Un- 

 compahgre; Gl D, embracing i)ortions of Southern Colorado, and lying 

 principally in the drainage-basin of the Eio Grande ; G5 D, embracing a 

 l)Ortion of Southeastern California, showing the interior basin of Pana- 

 mint and Death Valleys, Amargosa Eiver and Owens Lake drainage ; 

 69 B, Southern Colorado and Northern New Mexico, lying principally 

 in the drainage-basins of the Eio Grande, Conejos, Chama, and Navajo 

 rivers ; 70 A, Southern Colorado and Northern New Mexico, showing 

 the drainage-basins of the Purgatory and Canadian rivers, and Costilla 

 and Culebra creeks ; 70 C, Northern New Mexico, and drainage-basins 

 of the Canadian and Mora rivers; and 77 B, embracing portions of 

 Central New Mexico, and lying in the drainage-basins of the Eio Grande 

 and Pecos rivers. 



All these sheets except 53 C and 61 D show economic features of the 

 areas represented by arrangement of colors. 



A temporary field office has been established at Ogden, where time 

 and meteorological observations are being taken, and the further topo- 

 graphical and hydrographical survey of the Great Salt Lake basin is 

 being carried forward by a special party. 



During the year, volume IV of the quarto reports on Paleontology 

 has been published, and volume II, on Astronomy and Barometric Hyp- 

 sometry, is passing through the press; as is also a catalogue of the 

 mean declinations of 2,018 stars, which useful work will supply all the 

 needed latitude stars for the entire area west of the one hundredth me- 

 ridian from latitude 30° to 60° N. During that part of each year, i. e., 

 from May to December, in which the season is best adapted for such 

 observations, it will appear that this Survey, having at its base the sys- 

 tematic collection by the most scientific method of topographical data 

 for an accurate map of the Western mountain region, has gone on with 

 its usual vigor, having now prosecuted its labors in the States and Ter- 

 ritories of Texas, Colorado, Nebraska, California, Nevada, Oregon, New 

 Mexico, Arizona, Utah, Wyoming, Idaho, and Montana, and already 

 published original maps covering an area of 242,598 square miles. It 

 will be seen that considerable progress has been made toward the com- 

 pletion of the great topographical map, on a scale of one inch to eight 

 miles, that will embrace an approximate area of 1,413,300 square miles; 

 or an area considerably larger than that embraced by all the States lying 

 east of the Mississippi Eiver. 



