470 
SILTJKIA. 
[Chap. XIX. 
not less than 400 miles, and over an area larger than France. As in America, 
we found gold in the granite of Ekaterinburg, in the syenite of Peschanka, and 
in the greenstones around Alexandrofsk, as well as in the debris of the quartz- 
veins which had penetrated the older deposits. Now, as the granitic and dioritic 
rocks of the Ural were unquestionably emitted at different periods, it follows 
that the data laid before geologists nearly a quarter of a century ago are so far 
in harmony with the observations of Mr. I). Forbes. At the same time, although 
we gave clear proofs of the comparative recency of the production of gold in 
the Ural Mountains, we did not prove, as he did, that the latest of these auri- 
ferous impregnations or emanations was posterior to the formation of the 
Secondary rocks. It is, however, quite possible that future observers, who have 
more time at their disposal than we possessed, may discover that the greenstones 
and porphyries which have penetrated the Jurassic rocks in the Southern Ural 
have also impregnated them with a small amount of gold. 
The newest or post- Jurassic origin of gold is also that to which attention has 
recently been attracted by Mr. Whitney, a well-known geologist of the United 
States, whose work on California * is replete with excellent observations on the 
physical geography, geology, and natural history of that country. The following 
conclusion of this author cannot, however, be allowed to pass without a comment. 
After showing that some gold is found in altered strata of Triassic, Jurassic, 
and Cretaceous age, which are in contact with, or adjacent to, auriferous granite, 
he says, " While we are fully justified in saying that a large portion of the auri- 
ferous rocks of California consist of metamorphic Triassic and Jurassic strata, 
we have not a particle of evidence to uphold the theory that has been so often 
maintained, that all, or even a portion, of the auriferous slates are older than 
the Carboniferous We are able to state, referring to the theory of the occur- 
rence of gold being chiefly limited to Silurian rocks, that this metal occurs in 
no inconsiderable quantity in metamorphic rocks belonging as high up in the 
series as the Cretaceous "f. I presume that Mr. Whitney applies this view to 
California only ; for he must be aware, without quitting his own vast continent, 
that the chief seats of gold, in North as well as in South America, are in the 
quartz-veins of slaty rocks for the most part older than the Devonian rocks, and 
that all these cases agree with the ascertained facts in Australia, New Zealand, 
Asia, and Europe, and even in all the well-examined tracts of Eastern North 
America. Denying that I have been warped by any theory in my former attempt 
at a generalization on this subject, and declaring that I was guided solely by the 
facts then known to me, I have at the same time much satisfaction in acknow- 
ledging the additions made to that knowledge, first by Mr. D. Forbes, and 
recently by Mr. Whitney and his associates. 
Yet, no one who peruses the work of our Transatlantic cotemporaries can fail 
to see that several of the phenomena are still involved in obscurity, and that 
some of them even tell against the novel portion of their conclusions. For ex- 
ample, in the early part of the volume in which the Coast Ranges are de- 
scribed, and in which cinnabar and copper are shown to be worked amongst me- 
tamorphosed Secondary and even Tertiary and eruptive rocks, it does not appear 
that gold has ever been profitably worked in these extensive ranges north and 
south of San Francisco, although many varieties of highly metamorphosed 
Secondary rocks, up to the Cretaceous inclusive, occur in them, jaspers, ser- 
* Geol. Surv. California: Geology, vol. i. 1865. me to prove most distinctly that these so-called 
t Silliman's Americ. Journ. s. 2. vol. xxxviii. ' slates ' are merely shales altered and impregnated 
p. 261. With regard to the 'auriferous slates ' of with gold and other metallic compounds in the 
California, Mr. D. Forbes has called my attention manner described by him. (See also Geological 
to a series of specimens, some of which appear to Magazine, vol. iii. Sept. 1866.) 
