58 APPENDIX TO REPORT OF THE SECRETARY. 



of arable land are at hand. Areas of pasture and timber land are also 

 noted. 



During tlie whole season, of four mouths' duration, the weather was 

 unexceptiouably favorable for the prosecution of the work ; scarcely a 

 day was lost from bad weather by any of the parties. 



The total area surveyed during the season, and to be mapped during 

 the winter, was about 29,000 square miles, a very considerable addition 

 to our knowledge of the Western country. 



In succeeding years the work is to be extended toward the north, 

 east, and west. 



Geologi/.— The geological field-work of the survey for 1877 was as- 

 signed to Dr. F. M. Endlich, Prof. Orestes H. St. John, and Dr. A. C. 

 Peale, in the Sweetwater, Teton, and Green Eiver districts respectively. 

 Many interesting geological facts were observed which will be detailed 

 in the annual report of the survey. 



The Sweetwater district comprised a well diversified country. The 

 eastern portion of the Green River Basin was found to be underlaid 

 with Tertiary formations, with isolated volcanic eruptions at several 

 points. The prevailing westerly winds of the region have resulted in 

 the formation of sand dunes wherever the configuration of the country 

 has offered an obstacle to the progress of the sand that is formed from 

 the readily disintegrating Tertiary sandstones. On the eastern side of 

 the Wind River Mountains a full series of the sedimentary formations 

 was noted, beginning with the Silurian, and numerous stratigraphical 

 phenomena were observed and studied with a view to the determina- 

 tion of the age of the mountain-range. 



Camp Stambaugh, at the south end of the range, is located within 

 the area of the oldest metamorphic rocks of the district In these, gold 

 has been found in varying quantities for the last ten years, and, at one 

 time, the region was the scene of considerable mining excitement. 



The western side of the Wind River Mountains was found to be very 

 interesting on account of the remains of enormous ancient glaciers. 

 Moraines, covering many square miles, and often a thousand feet in 

 thickness, extend downward through narrow valleys that now contain 

 rushing streams. Striation, grooving, and mirror-like polish of rock in 

 sitUj denote the course taken by the moving ice-fields that have left 

 these marks of their former existence. From all indications, the cessa- 

 tion of glacial activity must have occurred within a comparatively recent 

 time. Scarcely any vegetation has sprung up on the light glacial soil, 

 and the characteristic distribution of erratic material bears every evi- 

 dence of " freshness." 



All along the Sweetwater River the characteristic Sweetwater group 

 of the Tertiary was found, continuing northward to the hills opposite 

 Semiuoe Pass. These hills were found to be projections of granite that 

 during the Tertiary epoch, and probably long before, existed as islands 

 in a widely extended sea. 



On the south side of the Sweetwater, in the Seminoe Hills, the older 



