Lower Palaeozoic Rocks of the South-East of Ireland. 



605 



the felspar in the analysis of the granite ; we have the following equations from 

 Tables III., V. and VI., to determine these eight unknown magnitudes: — 



7207 = 100 ? + 44-58 m + 35-55 I +f^ 



1481 = 32-13 TO + 17-08 l+f„i 



222 = 4-57 m + 29-81 I +f 



163 = 0-78 VI + 0-61 I +f 



33 = 0-76 711 + 3-07 I +/„ 



511= 10-67 m+ 9-45 l+f, 



279 = 0-95 m + 0-35 I +f. 



109 = 5-34 m + 4-30 I +/; 



(21) 



From these equations we may find the following Table, containing the 

 distribution of the various chemical elements of the granite rock among its 

 component minerals : — 



Table VIII. 

 Distribution of Elements among the Granite Minerals. 



Converting the column of felspar into per-centages, we find the following 

 Table, which contains the calculated felspar of the granite, including its ortho- 

 clase, which we promised (page 593) to compare with the average result of 

 the various direct experiments made on the felspar of the granite of the Three 

 Rock Mountain. The present calculation gives a slight preponderance of 

 potash over soda in the ratio of 8 : 7, while the direct experiments gave, for 



VOL. XXIII. 4 K 



