62 Royal Society 



IV. White Mica. 



Silica 44-40 



Fluosilieon(SiF 3 ) 0-16 



Alumina r 37*36 



Peroxide of iron 2*04 



Lime 078 



Magnesia 0*57 



Soda 0^93 



Potash 9*87 



Protoxide of manganese 0*24 



Water 1'84 



98*19 



The specimen of Mica here analyzed came from veins in the 

 Granite quarry of Rubislaw, near Aberdeen, and occurs in large 

 plates, associated with red Orthoclase. It was carefully examined 

 for lithia, but no trace of this alkali could be found in it. 



The angles of the rhombic plates were 60° and 120° exactly, and 

 the angle between its optic axes was found to be 72° 30'. 



The black Mica in large crystals is very rare, but it seems abun- 

 dantly disseminated in minute scales through most of the Scotch 

 Granites. The following analysis was made on specimens found near 

 Aberdeen by Prof. Nicol, and kindly forwarded to me by him, for 

 the purposes of this paper : — 



V. Black Mica. 



Silica 36-50 



Alumina 16-50 



Peroxide of iron 18*49 



Lime , 1*11 



Magnesia « . . 7*44 



Soda 0-92 



Potash 8-77 



Protoxide of iron 6'76 



Protoxide of manganese 1*80 



Water 1-60 



99-89 



This mica was carefully examined for fluorine, and found not to 

 contain any. 



"Researches on Vanadium."- — Part III. Preliminary Notice. By 

 Henry E. Roscoe, B.A., F.R.S. 



I. Metallic Vanadium** 



In the second part of "Researches on Vanadium," it was stated 



* Phil. Trans. 1809, p. 679. 



