248 
2. Of grey color, yielding a light reddish powder and very fine- 
grained, 
95°72 Insoluble in acid. 
80°23 SiO; (80°53—0°30) 
15:49 Bases combined with silica. 
Undissolved bases, and combined with silica. 
Al.03==9°80 
CaO =0°30 
MgO —0:32 
NaO =5-30 
15°72 These fizures agree sufficiently. 
In calculating the amount of Alumina again, required by 
the protoxides we find: 
CaO = 0°30 = Al.O; = 0°55 
MgO = 0°32 = Al.0O; = 0°82 
10°17 
agreeing closely enough with the amount found, to warrant 
the supposition of having belonged to feldspar. 
INO 325730 Seo 
CaO = 0°30) _ nae 
MgO = 0:32 fir a 
15-72 84-74 
15°72 
50:46 Albite. 
In determining the quartz in the way indicated, we find it 
to amount to 
95-72 Insoluble in acid. 
50:46 Albite. 80.23 Silica total. 
34:74 Silica of Albite. 
45°26 
0:23 45:49 Quartz. 
45°49 Quartz. 
