824 DESCRIPTIVE GEOLOG"Y. 



Analio Island lies 3 miles from the eastern shore, and rises somewhat 

 boldly out of the water. A measurement made by Mr. J. D. Hague with 

 a pocket-level j)laces the summit at 507 feet, and the highest observed 

 deposit of tufa at 470 feet above the lake. As terrace-lines have been 

 seen nearly 500 feet above the water's edge, it seems highly probable that 

 the top of the island may at some time have been submerged beneath La 

 Hontan waters. Geologically the island consists of dark-gray trachyte, 

 possessing a fine-grained groundmass, scattered through which are large 

 crystals of feldspar and occasional fragments of hornblende, the rock 

 breaking with a rough hackly fracture. 



Prof 0. D. Allen examined the water collected from Pyramid Lake, 

 and reported the following : 



Specific gravity, 1.0027. 



Fixed matter in 1000 parts, 3.275. 



Constituents determined in 1000 parts: 



Magnesia 0.1292 



Sodium .• 0.8999 



Soda 0.4234 



Chlorine 1.3870 



Sulphuric acid 0.1400 



Carbonate of lime 0.0178 



Carbonic acid 0.2392 



3.2365 



There are present in sniall quantities, but not quantitatively estimated, 

 potassa, lithia, silica, and boracic acid. 



Virginia Eange.^- — ^Within the belt of the Fortieth Parallel Survey, the 

 Virginia Range forms the first of the great series of meridional ranges 

 lying to the eastward of the Sierra Nevada, which so characteristically 

 rib the basin, and presents, with the exception of the Pah-Ute Eange, a 

 more continuous and unbroken ridge than any of the other mountain 

 uplifts. It rises abruptly from the plain in latitude 38° 10', extending 



' lu part from notes furnished by Mr. Clarence King. 



