62 



Rocks of Koyang. 



The subjoined is the quantitative analysis of the same 

 rock : — 



No. 9. — Hornfels. 









Per cent. 



Molecular 





Eatio. 









Proportions. 







p 2 o 5 





•16 



•02 







Si0 2 







61-92 



.. 20-60 = 



Si0 2 



20-60 



A1 2 3 



^ 2 3 







20-74 

 2-28 



4-03) 

 •28/ - 



E 2 3 .. 



4-31 



FeO 







3-90 



1-08^ 







MnO 

 CaO 







•17 



•42 



•05 f 

 •15 ( ~ 



RO 



2-38 



MgO 







2-19 



no; 







K o 







2-28 



•49) 

 1-13 y = 

 2-35) 







Na 2 







3-51 



R 2 



3-97 



H 2 







2-12 











99-69 



31-28 







Hygroscopic 



moisture 



•92 







Specific 



gi 



avity 



2-738 







The subjoined calculation of the mineral percentages 

 agrees with the results of the microscopic examination, with 

 the exception that the combined water is in excess, and that 

 there is a small deficiency in the alumina. These discre- 

 pancies are probably due to analytical inaccuracy. 



