736 



DESCRIPTIVE GEOLOGY 



Mr. R. W. Woodward, who made the analyses, reports 



Silica 



Alumina 



Ferric oxide. 



Lime 



Magnesia . . . 



Soda 



Potassa 



Lithia 



Water 



1. 



1. 



2. 



2. 



76.80 



77.00 



74.62 



75.34 



11.64 



11.54 



11.96 



11.68 



1.10 



1.04 



1.09 



1.32 



0.43 



0.43 



0.36 



0.49 



trace 



trace 



trace 



trace 



2 53 



2.45 



2.26 



2.20 



6.69 



6.72 



7.76 



7.35 



trace 



trace 



trace 



trace 



0.77 



0.77 



1.02 



0.97 



99.96 



99.95 



99.07 



99.35 



Specific gravity. No. 1, 2.5 ; No. 2, 2.23. 



Both of these analyses are remarkably alike, and chemically vary but 

 slightly from the physically different rhyolites from the Pah-Ute Range, 

 of which analyses are given on pages 695 and 698. At the extreme south- 

 ern point of the Mopung -Hills, basalts again break out, overlying the 

 rhyolite, but occupying a very limited area. 



Resume. — Roughly the structure and dynamics of the West Humboldt 

 Range may be summed up in a few words. Its anticlinal fold strikes diag- 

 onally across the topographical trend, the axis of the fold being more or 

 less influenced by the Archaean mass of Wright's Caiion, in the region of 

 which there is some local displacement. The eastern side of the fold is 

 faulted down on the plane of the axis, and is for the most part wanting, the 

 position of the overlying limestone indicating that the northern continua- 

 tion has suffered a powerful depression, leaving the western half high in the 

 air. A further remarkable peculiarity is the similar absence of the southern 

 extension of the eastern side of the fold, the high summits in the region of 

 Buffalo Peak falling off rapidly to the southwest without change of strike 

 until they meet the line of the supposed northwest and southeast fault, and 

 are there abruptly cut off, and do not re-appear on the southerly continua- 

 tion of their strike. This cross-fault divides the rano-e into the north and 

 south halves just south of Sacramento Canon, moved the southern end in 



