428 Mr. J. A. Phillips's Notes on the Chemical Geology 



Water lost at 212° F 048 



Water lost by subsequent ignition. 6*16 



Silica 92-64 



Alumina 0*30 



Potash 0-27 



Lime, iron, and soda .... traces 



99-85 



This veinstone, which exhibited numerous parallel bands in 

 the direction of the enclosing walls, was selected for analysis as 

 having been most recently formed. On boiling 35*18 grains of 

 this substance in a finely divided state during eight hours in 4 oz. 

 of a strong solution of caustic potash, only 2*35 grains, or 6'68 

 per cent., of the silica present was dissolved. 



A section of this substance examined under the microscope 

 showed the reniform structure of chalcedony, together with 

 patches ,of amorphous silica and small crystals of iron pyrites; 

 but no other appearance of crystallization could be detected. This 

 specimen contained a well-defined fluid-cavity, in which the va- 

 cuity occupied about one- tenth of its total volume. Another 

 portion of the deposit, which, from being further removed from 

 the sides of the fissure, must have been of older date, afforded 

 only 4*72 per cent, of water, and distinctly showed the presence 

 of crystalline silica. On carefully examining the great western 

 vein before alluded to, considerable quantities of chalcedony were 

 found ; and in one of the cavities a few small perfectly defined 

 crystals of quartz were discovered. 



Alkaline Lakes. 



In that portion of California lying on the east of the Sierra 

 Nevada are Mono Lake and Owen's Lake, both considerable 

 sheets of water highly impregnated with alkaline salts. Owen's 

 Lake, at the southern extremity of which I was for some weeks 

 encamped during the fall of 1865, lies in lat. 36° 20' south, 

 long. 118° west from Greenwich, is about twenty miles in length 

 and eight in width. Owen's Valley is a narrow basin enclosed be- 

 tween high mountains, and has a length of about 140 miles, and 

 an average width of 10 miles. On its western side it is bordered 

 by the Sierra Nevada, which opposite the lake rises in peaks 

 fourteen thousand feet in height. On the eastern side the 

 mountains are more broken, although of nearly equal height, 

 but nothing like a complete exploration of this region has yet 

 been attempted ; besides which it is so utterly barren and for- 

 bidding that the Indians, whose stronghold it still remains, are 

 not likely for some time to be much interfered with by the in- 

 defatigable mining " prospecter." These mountains are bare, 



