Minerals in Dacilr. 537 



by the specific gravities, jrivinj:: the Lcravinietric proportions of 

 the different minerals from whicli the percentages by weight 

 were obtained. 



A number of determinations of the felspar phenocrysts by the 

 Michel-Ldvy method resulted in the majority of them giving 

 extinction angles for A\\ Anj but an occasional one for Ab.^, 

 An.,. Tlie specific gravities of hypersthene and ilmenite were 

 determined by means of a small specific gravity bottle, while 

 that of the biotite was determined by floating flakes in any 

 position in a solution of Methylene Iodide m benzine, and then 

 determining the specific gravity of the solution by a Westphal 

 balance. 



The specific gravity of the felspar |thcnocrysts was determined 

 from a knowledge of their composition and reference to tables. 



Calcul.\tion of JMode. 



1 As Phenocrysts and in the Hypersthene. 



2 Including- 0.15 per cent. WOr, and 0.16 per cent. S(FeS2). 



