54 



tated by ammonia ; and after the remaining sulphates had been con- 

 verted into carbonates by acetate of lead, and the carbonates of soda 

 and potassa into chlorides, the joint weight of these two chlorides was 

 ascertained, and the chloride of potassium afterwards separated by 

 chloroplatinatc of sodium and alcohol. The results thus obtained 

 were as follows : 

 Felspar, from the granitic vein at Tucker 's quarry, six miles N. 

 W. of Wilmington. 

 1st variety. (Orthoclas.) 



Colour white; lustre vitreous, inclining to pearly; translucent. 

 Fracture distinctly rhomboidal, traversed by innumerous parallel 

 cracks or fissures, which impart to it a milky or opaque appearance. 

 Specific gravity in piece, 2.562, in powder, 2.585, at temperature 

 69° F. 



Composition in 100 parts. 



Silica .... 



. 65.24 



Alumina . 



. 19.02 



Peroxide of Iron 



a trace 



Magnesia . 



0.13 



Lime .... 



. 0.33 



Soda .... 



3.06 



Potassa . . . 



. 11.94 



Oxygen. 

 33.89 



0.050 1 

 0-092 ! 2q4R | 

 0.782 f 2 ' 948 J 

 2.024 j 



^ 11.83 



99.72 



2d variety. (Albite.) 



Colour white, transparent ; lustre pearly, inclined to vitreous. Frac- 

 ture more irregular; the surface of the fracture striated, curved, or 

 exhibiting obtuse angles. Hardness slightly inferior to the former. 

 It fuses with great difficulty before the blow-pipe, but is slightly more 

 fusible than the preceding. Specific gravity in piece 2.612, at 71° F. 



Composition in 100 parts. 



Silica .... 



. . 65.46 . . 



Alumina 



. 20.74 . . 



Peroxide of Iron . 



. 0.54 . . 



Magnesia . . . 



0.74 . . 



Lime .... 



0.71 . . 



Soda .... 



. 8.98 . . 



Potassa . . . . 



1.80 . . 



Oxygen 

 34.01 

 9.685 

 0.165 

 0.286-) 



2:552 f 3 - 87 J 



0.305 J 



\ 9.85 1 



} 13.22 



99.97 



Mr. Boye remarked, that felspar being a double oxysalt of two 



