76 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
L. Hypersthene andesite, northwest of Red Bluff. Tonalose. Contains plagioclase 
and pyroxene, with an amorphous glassy base, and sometimes olivine altered to 
chloritic matter. 
M. Peridotite, var. wehrlite, hills 3 miles northwest of Red Bluff. Wehrlose. Con- 
tains olivine, diallage, brown mica, rarely plagioclase, and secondary iron oxides. 
Sp. gr., 3.37. Analyses J, K, L, and M by Eakins, record No. 1266. P. R. C. 975 and 
976. 
The following rocks, at first supposed to be Pliocene sandstones, were also described 
by Merrill, Am. Jour. Sci., 3d ser., 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. 
Tron and alumina weighed together. The iron is mostly in the ferrous form. 
A B. Cc. 
SiO» 65. 76 68. 92 
AkO. 17.18 16. 22 
MgO trace trace 
CaO... 2. 30 1.62 
NazO 2.22 1.56 
K20 3.14 4.00 
B20 at 105° 3. 46 1.60 
H20 at red heat 5.60 6. 00 
99.66 | 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. 146. Gallatin 
Valley. P. R. C. 58. 
