374 The Ameiican Geologist. December, i9oo 
The manganese-iron separations were made by precipitat- 
ing the iron as a basic acetate in a boiling solution ; less fre- 
quently by precipitating the iron by means of barium car- 
bonate. 
The water determinations were not made directly, but by 
loss on ignition, oxidation and reduction being avoided as far 
as practicable. They therefore include scarcely appreciable 
traces of F (or CI) in many cases, as well as occasional traces 
of CO-' and S. In the quartz gabbro the CO^ is doubtless more 
important, and may reach i.oo%. 
Results of the Analyses. The rock analyses scattered 
through the preceding pages can be grouped as follows : 
<B O 
03 = 
cs 
.a 
C 03 
c52 
It 
.5S . 
I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
VIII. 
IX. 
SiOj 
47.70 
47.90 
49.18 
49.78 
35.81 
49.06 
52.84 
56.60 
21.50 
TiOa 
1.80 
.57 
1.09 
2.30 
1.46 
Trace 
1 59 
Trace 
AUOs 
19.04 
19.92 
19.01 
29.37 
14.32 
15.33 
23.62 
17.84 
8.02 
FOaOs 
.87 
4.92 
.89 
.34 
7.38 
5.92 
.65 
2.55 
30.54 
Feb 
8.84 
9.78 
7.79 
.60 
15.25 
11.53 
10.00 
4.09 
as. 53 
MnO 
Trace 
Trace 
.51 
.08 
.18 
.61 
.43 
Trace 
.32 
MgO 
8.65 
4.55 
6.42 
• 1.01 
10.49 
2.75 
3.16 
3.16 
1.95 
CaO 
8.96 
8.56 
0.12 
11.86 
7.23 
0.80 
3.92 
6.28 
1.55 
Na,0 
2.53 
2.75 
3.32 
4.39 
2.06 
3.17 
2.64 
4.45 
.42 
K.6 
.53 
.56 
.82 
.46 
.37 
1.40 
.67 
.45 
.10 
HoO 
1.38 
.76 
2.06 
1.76 
5.23 
1.76 
1.87 
3.20 
'^.77 
P.O. 
.27 
.14 
100.30 100.27 100.21 99.65 100.62 100.06 99.80 100.35 100.70 
Sp. Gr. 2.89 2.93 2.84 2.676 3.08 2.84 2.83 2.38 4.02 
I. Olivine gabbro (1136), from a point about a half a mile west 
of the line between Sec. 31, 62-11 and Sec. 6, 61-11, in T. 61. near 
Birch lake. A trace of CO2 occurs; P2O; and Fl (or CD also pres- 
ent in apatite in very small amount. No appreciable BaO, nor 
SrO; no other elements determined. 
II. Diabase, poor in olivine (954) from the east side of Birch 
lake on N. W. ^4 Sec. 17, 61-1T. Traces of P.O5, F (or CI) .CO2. and 
S are shown by the mineralogical composition; no appreciable BaO, 
nor SrO; no other elements determined. 
III. Olivine diabase (1843), from the extremity of Pigeon point. 
Traces of PzOs, F (or CI), and the rare metals of the cerium and 
yttrium groups occur in apatite and allanite; no appreciable BaO. 
nor SrO. nor Li^O; no other elements determined. 
