602 Mr. J. B. Jukes and the Rev. Samuel Haughton on the 



Atomic weight of margarodite = 302. 



The atomic weight of lepidomelane is thus found ; its equation in atoms 



(6), is 



9 silica. 



7 peroxides. 

 6 protoxides. 

 5 water. 



If X and y denote, as before, the atomic weights of the compound atoms of 

 peroxides and protoxides, we find from Table V. the following : — 



from which we obtain. 



40-78 = 0-624 a;, 



18-98 = 0-538 2/; ^ ' 



y=S5. 



And since the atomic weight of lepidomelane is 



9x4.5 + 7x + 6y + 5x9 ; 

 we obtain finally, 



Atomic weight of lepidomelane = 1115. 



Using the atomic weights just found, we find the following equations; 



denoting the unknown atomic weight of the felspar paste, including orthoclase, 



by 0: — 



rj =45(2, 



m = 402Jf, 



I =1115L, (B) 



f -<I>F: 



q +»n + /+/= 10005; 



the last equation being found from the consideration that all the per-centages 

 of constituent minerals, taken together, must make up the entire analysis of the 

 rock given in Tables VI. and VII. 



So far as we have hitherto gone, equations (B) add nothing to equations 

 (A), as they are five in number, and contain five unknown quantities in 

 addition to Q, F, M, L. viz., </,/, w?, /, 4>. 



