770 DESCRIPTIVE GEOLOGY. 



1. 

 Silica 41.28 



Alumina - .* - . 1 1 .03 



Ferric oxide - 13.82 



Lime 8.75 



Magnesia - 6.49 



Soda 0.62 



Potassa - 0.65 



Water 1 7.36 ' 



2. 



36.93 



3. 



37.57 



11.56 • 



15.18 



10.71 



13.07 



7.95 



6.02 



6.28 



5.58 



0.55 



0.79 



0.78 



2.17 



25 24 



19.61 



100.00 100.00 100.00 



It is worthy of note that the palagonite from Java is described by 

 Junghuhn as forming a stratum in the Tertiary sedimentary hills. 



South of Mirage Station, there is a bold, conical hill that rises as an 

 outlier on the northwest flank of the group. This is seen to be composed 

 of infusorial silica, having a dip of about 18° to the northwest ; basalt lying- 

 in the eroded edges of the strata. At this point, the upper part of the infu- 

 sorial beds consists of yellow sandy strata, which are underlaid by the clear 

 white silica, and that again underlaid by a gritty sandstone, in which beds 

 of more or less thickness of palagonite tufa begin to appear. The local ero- 

 sion does not display the rock sufficiently to get at the solid beds of palago- 

 nite below. On the north side of the valley, at White Plains, the infusorial 

 series outcrop in a ravine,- striking northeast true, and dipping southeast. 

 In a ravine east of White Plains, at the bottom of the infusorial series, is 

 again seen the uppermost limits of the palagonite. In the middle of the plain, 

 a little west of Mirage Station, a well has been sunk, which cuts the lower 

 beds of the infusorial silica, passing down into the palagonite. 



Following northwest across the strike of these infusorial beds in the 

 region of the sunken well, and rising constantly in the series of strata,, 

 there appear the coarse, gritty sandstones and the saccharoidal limestones, 

 developed very thinly, and next above these a great series, attaining cer- 

 tainly 1,200 feet in thickness, of gray, vesicular, volcanic tufas, which are 

 undoubtedly of the same age as the beds found in Indian Pass, Montezuma 

 Range. Throughout the palagonite tufas are more or less infusorial beds. 



