KAWSOH MOUNTAINS. 769 



pearance, varying from a fine-grained, yellowish-brown volcanic ash, to 

 coarse, scoriaceous, brecciated beds, highly altered and decomposed, the 

 binding material being characteristic palagonite. The specimens collected 

 from Fossil Hill are of the latter kind, containing many included basic frag- 

 ments, completely surrounded by amorphous material. Portions of it, 

 treated with acid, indicate the presence of soluble carbonates. Under the 

 microscope, much of the material is clearly shown to be derived from the 

 decomposition of augite. A specimen of the palagonite tufa from Hawes 

 Station, on the Carson River, just below the southern boundary of the map, 

 has been submitted to analysis by Mr. R. W. Woodward, who reports as the 

 ultimate composition : 



Silica 50.87 50.88 



Alumina 14.86 14.37 



Ferric oxide : 13.02 13.30 



Lime... 6.08 6.18 



Magnesia .' 4.08 4.14 



Soda 1.76 1.86 



Potassa • 0.85 0.93 



Water 8.48 8.34 



100.00 100.00 



This Nevada palagonite contains a higher percentage of silica and less 

 water than the tufa found in other portions of the globe, notably Iceland, 

 Galapagos Islands, and Java. 



For the purposes of comparison, there are subjoined here three analyses 

 from these distant localities : 



1. Palagonite from Iceland, collected between Thingvellir Lake and 

 the Geyser (Bunsen). 



2. James Island, Galapagos (Bunsen)^ 



3. Dyampang-Kulon, Java (Prolss)^ 



1 Poggendorf. Annal., 1851, 219. 

 ^Neues Jahrbuch fur Mineralogie, 1864, 434. 

 49 D G 



