134 Scientific Intelligence. 
the soda and decrease the alumina and silica. ues would per 
haps account also by its fluorine for a loss of 11°68 per cent in 
Mr. Rand’s analysis. my samples, I. was not entirely fi 
from cryolite; II. was more so, and III. I should judge seal 
entirely. 
3. Notes on the Chemical ha! Aa se Eu, sel of es. 
nia; by RTHUR Puiiups. nica 
the Sierra Nev sth beginning in the mete bbabasea Tejou " 
and extending through the state to its northern ; 
sequence, es of visioti local citviimstniiees, different or 
Phe slates of the auriferous belt have been shown by Professor 
Whitney to belong, for a great pe to the Jurassic period, al- 
though the occurrence of numerous Triassic fossils in the gold- 
aring rocks of Plumas onatley pe elsewhere renders it more 
than probable that no inconsiderable portion of the slates in the 
heart of the gold region are of that age. . 
e rock constituting the gre at mass of the Sierra Nevadais | 
a apa bate sata onl oportion of quartz, and mM = 
viet e species of eudspar (oligos) is generally found. 
: or 
beard” mass of granite formiiniy this more elevated portions of the = 
a are found various crystalline rocks, such i syenites, diorites, | 
and porphyries veiis _ 4 
rtz Veins.—The matrix or gangue of the auriferous veins 
of California is invariabl quartz, which is generally erystalline 
in its structure, or partially vitreous and semi-transparent. In the 
majority of cases the he bg sated an auriferous veinstone 
is ribboned in such a way as to form a succession of layers parak | 
lel with the leas of the lode iteelf: and some one or more of thes®@ | 
lamin are not unfrequently far more productive than all the 
others. In some instances these parallel bands are separated from 
each other by a thin layer of quartz, slightly differing, either in 
_ color or struct hat forming the seams themselves; % 
mae may be only distinguished by a difference of color of two 
djoining members of the se ; 
many cases, however, aa of the enclosing slates avis . 
the vein into distinct ban ds; and in such instances it wil ee 
served that the thickness of the interposed fragments of slate rf 
im Ee riiiedt aper. 
uartz occur in all the 
Said veins of the coun untry; and a certain amount of eryst® 
zation "ot also not a han of wh remarked along the ge of 
ata ae. several bands of which a vein is composed. 
‘dition z,in a more or less aa ee ‘ices 
amorphous hydrated ty or semiopal, and shalocdony are occa” 
