The Rev. Samuel Haughton on the Granites of Scotland. 61 

 The oxygen ratios of the Oligoclase are as follow : — 



No. 1. No. 2. 



Silica 32-191 32-128 



Alumina 10-843 11-590 



Lime 1-339 1*400 



Soda 2-360 2-082 



Potash 0-072 0-16.5 



46-805 47-365 



Hence we obtain : — 



No. 1. No. 2. 



Silica 8-54 8-82 



Peroxides 2'88 3'18 



Protoxides l'OO l'OO 



These oxygen ratios prove the felspars to be Oligoclase. 



III. Albite. 



Silica 68-00 



Alumina 20'00 



Lime 035 



Magnesia » . trace. 



Soda 10-88 



Potash 0-68 



99-91 



This Albite occurs at Stirling Hill, near Peterhead, in eruptive 

 Granite, and is found associated with red Orthoclase in veins ; it 

 encrusts the large crystals of Orthoclase, and is semitranslucent, and 

 is generally stained on the surface by peroxide of iron. 



Oxygen Ratios. 



Silica 35-306 11 77 



Alumina 9*348 311 



Lime 0-099 



Soda 2-790 \.> 1-00 



Potash 0-114 



This mineral is evidently a typical Albite. 



There are two kinds of Mica found in the Scotch Granites, and 

 both Micas resemble very closely the corresponding minerals of the 

 Donegal Granites. 



