WEST HUMBOLDT RANGE. 731 



mainly of the products of decomposition derived from the oxidation of sul- 

 phurets. Here, however, although scarcely any study has been made of 

 the vein products, good specimens have been obtained of native silver, 

 argentite, stephanite, pyrargyrite, kerargyrite, galena, blende, jamesonite, 

 bournonite, tetrahedrite, stibnite, anglesite, cerusite, malachite, azurite, 

 calcite, quartz, iron pyrites, copper pyrites. Xanthocone in .small crj^stals 

 is said to have been found in the Manitowoc mine, on the ridge between 

 Buena Vista and Cottonwood Canons. 



East of Buffalo Peak, and occupying the middle of the Quaternary 

 plain, is an alkali flat, about 12 miles in length by 4 miles in breadth, 

 formed of horizontal clay beds of the Lower Quaternary, which, along the 

 edges and over a greater part of the surface, are covered by a heavy ef&o- 

 rescence of sulphates and chlorides. 



Prof. 0. D. Allen, of Yale College, who analyzed this salt, collected 

 from near Buffalo Spring, found the following admixture : 



Chloride of sodium 70.81 



Sulphate of soda 26.38 



Sulphate of potassa . . . . 1.94 



99.13 



The aqueous solution was feebly alkaline, contained slight traces of 

 lithium and calcium, and gave, after concentration, a reaction for boracic 

 acid. 



SouTHERisr Region. — The southern half of the range has been much 

 less studied than the northern end, and it is even still more difficult to 

 obtain definite ideas of its structure. Unlike the northern end, however, 

 the geographical and geological axes approximately agree, the uplift, as 

 before mentioned, having a northeast and southwest trend. In general, it 

 seems to be a prolongation southward of the west side of the main anticlinal 

 axis, made up for a distance of 20 miles of highly inclined and much meta- 

 morphosed strata, and plunging suddenly downward near the line of the For- 

 tieth Parallel. 



It consists of quartzitic schists as the lowest member, which only in 

 the deepest points are laid bare by erosion. Over this, a heavy bod}^ of lime- 



