314 Rev. Samuel Haughton on the Granites of Scotland. [Apr. 7, 



it is greyish white, semitranslucent, in large striated crystals, and re- 

 sembles the Oligoclase of Ytterby, in Sweden. 



The oxygen ratios of the Oligoclase are as follow : — 





No. 1. 



No. 2. 





, 32-191 



32-128 





; 10-843 



11-590 







1-400 



Soda 



2-360 



2-082 





0-072 



0-165 





46-805 



47-365 



Hence we obtain : — 









No. 1. 



No. 2. 







8-82 





2-88 



3-18 





, 1*00 



i'oo 



These oxygen ratios prove the felspars to be Oligoclase. 



III. Albite. 



Silica 68-00 



Alumina 20*00 



Lime 0*35 



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 3- 11 



Lime 0"099 \ 



Soda 2-790 L. 1*00 



Potash 0-114 J 



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. 



