CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
115 
The following rocks, at first supposed to be Pliocene sandstones, were 
also described by Merrill, Amer. Journ. Sci., 3d series, vol. 32, p. 119. 
All consist of pumiceous volcanic glass. C, from Idaho, is included 
here for convenience. Analyses by J. E. Whitfield, record No. 382. 
A. Little Sage Creek. 
B. Devils Pathway. 
C. Marsh Creek Valley, Idaho. 
Iron and alumina weighed together. The iron is mostly in the fer- 
rous form. 
Si0 2 
A1 2 3 , Fe 2 8 -~ 
MgO 
CaO 
Na 2 
K 2 
H 2 Oat 105° 
FLO at red heat 
65.56 
18.24 
.72 
2.58 
2.08 
3.94 
1.12 
6.50 
100. 74 
65.76 
17. 18 
trace 
2.30 
2.22 
3.14 
3.46 
5.60 
68.92 
16.22 
trace 
1.62 
1.56 
4.00 
1.60 
6.00 
99.92 
The following examples of volcanic dust or sand, from the Gallatin 
Valley, were collected by A. C. Peale. Analyses A, B, C, and D by 
F. W. Clarke, record No. 379. Analysis E by H. N. Stokes, record 
No. 1314. 
A. Dry Creek Valley, above the mouth of Pass Creek. 
B, C. Near Bozeman. 
D. Near Fort Ellis. 
E. Essentially rhyolitic glass, described by Iddings in Bull. 150, 
p. 116. Gallatin Valley. 
A. 
B. 
c. 
D. 
E. 
Si0 2 
46.09 
| 14. 35 
61.82 
| 19. 86 
71.01 
| 15.17 
60.98 
j 21. 69 
68.68 
12.69 
1.14. 
1.17 
1.14 
1.11 
1.23 
5.58 
7.99 
tract 
A1 2 3 
Fe 2 3 
FeO . 
MgO 
1.29 
1.61 
| 1.47 
6.45 
.51 
1.78 
2.38 
1.31 
11.47 
.34 
1.19 
2.77 
2.97 
6.34 
1.33 
1.83 
.80 
1.23 
11.96 
CaO 
Na 2 
K 2 
Ignition 
MnO 
CaCO, 
28.72 
99.98 
99.13 
99.79 
99.82 
100. 73 
