94 CALIFORNIA ACADEMY OF SCIENCES [Proc. 41TH Ser. 
A sample of similar material taken from near the same place 
was analyzed by Dr. A. S. Eakle, of the University of Califor- 
nia, and was found to correspond very closely in composition to 
a true volcanic ash with an admixture of quartz sand and some 
other foreign minerals. His analysis, given below, differs 
from the foregoing in a manner that may be largely accounted 
for in this way. With a good magnifier nearly all of the 
samples showed clastic matter of this sort mingled with the 
ashy products, and the sample analyzed was not exceptional, 
but fairly representative of the great mass of this rock. It 
was taken from an old mine a few miles north of Poso station 
on the road to Granite. Dr. Eakle’s analysis follows: 
Silica SI @s yh ata eo ae ken ener ere 64.23 
Aliermmmiria (CAT E@ EN (Ce ne A IWRSS 
Berricroxiden(e,O3) ie eae gn ae 4.25 
Dire (CAO) ee! Sic MATS uakel 4.01 
Magnesia (Mic@) a ean Trace 
Potash K(REO tints et ee ar en: 158 
SodaviGNas Oy hac Ae eee ee eee 1.98 
LS UN ea iis aa A LARA mI MMA 1 hw) A 5), 68) 
SONS 
In the rock opened by mining there are casts of marine 
invertebrates, bones of marine vertebrates and the teeth of 
sharks. The lens reveals many minute scales of dark mica, 
and the confused granular surface of decayed felspathic matter 
and quartz sand. Several beds of this or similar material 
occur in this member of the Temblor, especially north of 
Poso Creek, where they form prominent outcrops at the sur- 
face, which are easily followed along their strike. 
A few outcrops of sand are sufficiently bituminous to induce 
drilling for oil, which has been done in different parts of the 
district, but thus far without satisfactory results. 
The fresh-water or brackish-water facies of the Neocene 
which was described some pages back, forms a local phase of 
the Temblor group. The difficulties to be overcome in making 
any division of the Temblor group upon the basis of litho- 
logical character become apparent when attempted in this 
quarter of the field. The more shaly portion is nearest the 
base, and the beds become coarser toward the top, though 
clays are distributed throughout the column. 
