Chap. XIX.] 
GOLD OF CALIFOENIA. 
471 
pentines, and mica-schists abounding in beds of the age of the Chalk. In the 
only situation, however, where gold-mining had been carried on to some extent 
in connexion with presumed Cretaceous rocks, the author avows that the age of 
these (metamorphic) rocks has been referred to the Cretaceous rather from general 
(lithological) analogy than from any direct evidence of fossils (p. 196). In the 
Genessee Valley, however, there are placer- workings on rocks containing Jurassic 
fossils (pp. 308 & 482) ; and in the Mariposa County a large quartz-vein, forming 
the Mount Bullion Ridge, and containing at some points gold enough to pay for 
working, crops out among hard shales and sandstones judged to be of Jurassic 
age from the Belemnites and other fossils found in them* (pp. xx, 226, & 482). 
Nevertheless it is only when the geologist traverses the wide longitudinal valley 
which separates the above-mentioned Coast Ranges from the great and much 
loftier Sierra Nevada, that he meets with those richly auriferous slates from 
which the great wealth of California has been derived f. Now several passages 
in Mr. Whitney's work clearly show that the chief body of these auriferous slates 
is of Palaeozoic age ; he even exhibits sectional diagrams representing the Creta- 
ceous and other Secondary conglomerates, shales, and sandstones as lying quite 
unconformably upon the edges of the vertical slaty gold-rocks (see pp. 211 & 354). 
Again, all the fossils found in the massive limestones which are intercalated in 
the upper portions of these auriferous slates being well known Carboniferous 
types, must not the inferior slates be of Devonian and Silurian age ? In various 
other passages descriptive of the highly metamorphosed sedimentary strata of 
various ages in California, up to the Miocene Tertiary inclusive, we perceive 
what vast difficulties any geologist must have had to encounter in drawing dis- 
tinct conclusions as to the age of many parts of these rocks ; but we do learn 
that in most cases the igneous rocks of the region, particularly the granites and 
diorites, are in themselves auriferous. Respecting the difficulties the author 
himself candidly says, "It was not possible to find any locality where these 
metamorphic rocks and the unaltered Cretaceous could be seen in contact ; and 
some difficulty was met with in clearly making out whether the metamorphic 
rocks might not themselves be of Cretaceous age. The weight of evidence, 
however, seemed to be decidedly in favour of the auriferous rocks being older 
than the Cretaceous " (p. 322). 
Seeing, therefore, that no other fossils have been detected in the richly auri- 
ferous slates of the Sierra Nevada save those of Palaeozoic age in the limestones, 
and that the association of gold-quartz with the Jurassic rocks of California is 
very rare, I can as yet see no valid reason to induce me to alter materially the 
generalization I adopted in my former editions, as derived from evidences in 
various parts of the world, viz. that the Silurian and associated Palaeozoic strata, 
together with the igneous rocks which penetrated them, have been the main re- 
cipients of gold. At the same time, I admit that small quantities of gold have, 
in "Western America, been eliminated during the Secondary period ; but these I 
consider to be exceptions to a general though not universal rule. 
The chief facts remain, therefore, as stated in my former edition. The general 
axiom which I would now further lay down is, that as no aqueous deposit of 
Primary, Secondary, or older Tertiary date has been ever found to contain gold 
* The Jurassic fossils at the gold-diggings of from the American Eiver, where gold-quartz- 
the Genessee Valley, California, were found in mining has been carried on : see his ' Catalogue of 
1863 by Messrs. Brewer and King. In the Mari- the Minerals of California,' 8vo, Sacramento, 
posa County, Jurassic fossils were found by Miss 1866. 
Errington in 1864, and others by Messrs. King and t Mr. D. Forbes has expressed to me the opinion 
Gabb. Professor Blake, who noticed Miss Erring- that not one-tenth part of the gold of South Ame- 
ton's fossils in 1864, had already in 1863 recog- rica is found in the Teinstones which have been 
nized an Ammonite (in Mr. Spear's Collection) intruded among the Secondary rocks. 
