74 
ANALYSES OF BOOKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
E. Feldspar separated from gabbro, southern half of sec. 14, T. 44 
N., R. 4 W., Wisconsin. 
F, G. Feldspars separated from olivine-diabase, NE. £ of sec. 13, 
T. 45 N.,R.1W., Wisconsin. 
Si0 2 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 105° . . . 
H 2 above 105 
MnO 
51. 99 
29.32 
1.23 
.63 
12.60 
2.91 
.28 
.03 
.54 
trace 
99.53 
61.65 
19.91 
2.28 
undet, 
.61 
4.12 
4.74 
5.72 
.95 
trace 
99.98 
G. 
56.15 
26.05 
1.98 
undet. 
.54 
8.70 
4.79 
1.56 
.13 
.64 
.13 
100. 67 
