688 DESCRIPTrVE GEOLOGY. 



Two springs, situated side by side, differed from the others observed, 

 in having a thin incrustation of hydrated oxide of iron upon the rock. 

 About 8 miles to the southward, on the summit of the low divide separating 

 Pleasant from Grass Valley, and closely related to the broad basaltic field 

 stretching eastward from the Pah-Ute Range, are two small mud springs, 

 which send out considerable water to the northward. The ground imme- 

 diately surrounding the springs is quite soft, and shakes and trembles under 

 the weight of a horse or mule. The mud from the springs has the composi- 

 tion of common clay. 



Pah-Ute Range. — This range lies directly westward of the Havallah 

 and Augusta Mountains, and forms one of the most prominent uplifts that 

 rib the Great Basin of Nevada. It extends from the valley of the Humboldt 

 River southward, with an unbroken persistent ridge for nearly 100 miles, 

 passing beyond the limits of this exploration. Owing to the large masses 

 of volcanic materialof Tertiary age, which, in so many places, have either 

 broken through the older Mesozoic strata or filled up the breaks in their con- 

 tinuity, the range varies considerably in width, but for the greater part of the 

 distance rarely measures more than 8 to 10 miles from base to base. From the 

 southern boundary of the map to Granite Mountain, in latitude 40° 15', the 

 trend is nearly northeast and southwest, beyond which it turns abruptly, be- 

 coming approximately north and south, parallel with the Havallah and West 

 Humboldt Ranges. Below Table Mountain, the range rises abruptly on the 

 west side, forming the eastern barrier of the ancient fresh-water lake-basin 

 of Nevada, which stretched across the dreary Carson and Humboldt Desert 

 westward to the Sierra Nevada Range of California, the elevation of the 

 desert in the region of Carson Lake being about 3,800 feet above sea-level. 

 Nowhere do the culminating points of the range reach any great elevation; 

 but inasmuch as the adjoining valleys are relatively depressed, the difference 

 in altitude is quite as well marked as in most of the Basin ranges, and the 

 more rugged summits, owing to the limited lateral extent of the uplift, 

 stand out even more boldly than in many other localities. Tarogqua Peak, 

 the highest point in the Pah-Ute uplift, nearly opposite the lowest depressions 

 of the adjoining valleys, has an altitude of 8,751 feet above sea-level and 

 4,800 feet above the Quaternary plains. Chataya Peak reaches an eleva- 



