THE VOLCANIC lloCKS OF ICELAND. 49 



Reddish-brown Rock from the summit of the Kasbeck, 



54. 



Found. Calculated. 



Silica 70-97 70*97 



Alumina and protoxide of iron . 18*13 17*45 



Lime 4*24 3*55 



Magnesia 1*54 1*62 



Potash and Soda 5*12 6*41 



100-00 100-00 



* ^ / 



I trachyte and 0*2533 pyroxenic mass. 



Rock from the summit of the Elbruz, 



55. 

 Found. Calculated, 



Silica . 69-65 6963 



Alumina and protoxide of iron . 19-85 18*25 



Lime 4-40 4*02 



Magnesia 2-27 1*92 



Potash and Soda 383 6-18 



100-00 10000 



1 trachyte and 0*3314 pyroxenic mass. 



Rock from Ararat, 



56. 

 Found. Calculated. 



Silica 65-96 65-96 



Alumina and protoxide of iron . 22*18 20*28 



Lime 4*27 5 39 



Magnesia 2*13 2*79 



Potash 1*34 2-23 



Soda 4*12 3*34 



10000 10000 



*. ^ ' 



1 trachyte and 0*6124 pyroxenic mass. 



Compact Porphyritic Rock from Ai'arat, 



57. 



Found. Calculated. 



Silica 65-27 65*27 



Alumina and protoxide of iron . 20*88 20-67 



Lime 657 565 



Magnesia 3-47 2*96 



Potash and Soda ...... 3*81 5*45 



100*00 100-00 



V I 



1 trachyte and 0*6786 pyroxenic mass. 

 SCIEN. UEM.^Nat. Phil Vol. I. Part I. E 



