448 
SILUEIA. 
[Chap. XIX. 
CHAPTER XIX. 
ON THE OEIGINAL INTEODUCTION OF GOLD INTO THE EAKTH'S 
CEUST AND ITS SUBSEQUENT DISTEIBUTION IN DEBEIS OVEE 
VARIOUS PARTS OF THE SUEEACE. 
CoNsrDEKnra the great quantity of Gold which has of late years been found 
in California and Australia, it may be expected that an author who has 
borne a part in the discussions upon this subject* should devote some 
pages to so engrossing a topic, — the more so as my chief article of belief 
has now proved to be true, viz. that the rocks which are the most aurife- 
rous belong to the Palaeozoic epochs, and especially to the Lower- Silurian 
age. At the same time I have to modify to some extent that aphorism ; 
for it will be shown that there are examples of auriferous igneous rocks and 
veinstones having been protruded into strata of Secondary age, the latter 
having become to some extent auriferous, — a fact unknown to me when the 
last edition of this work was published. The views now put forth will 
chiefly relate to the geological and mineralogical conditions under which 
gold has occurred. As a clear understanding of this point may tend, in 
some measure, to allay the fears of those who think that the metal may 
be discovered over regions vastly more enormous than the tracts to which 
it is restricted, certain geological and statistical data and arguments that 
I have advanced in greater detail in other works are here brought together. 
Let us first reflect upon the general fact that, whilst all the stratified 
formations are composed either of crystalline and Palaeozoic rocks or of 
Secondary and Tertiaiy deposits, gold has never been found in any appre- 
ciable quantity in either of the two last-mentioned classes of strata where 
they are in their natural state, i. e. where they have not been penetrated 
by igneous rocks or metamorphosed and impregnated with mineral veins. 
The vast areas, therefore, which are covered by all such younger unaltered 
formations are excluded from the general auriferous area ; and every one 
who lives in tracts the subsoil of which consists of such unaltered rocks, 
may at once be assured that he can never find gold in them. 
Having laid down this generalization, which affirms that by far the 
largest countries contain little or no gold, we proceed to consider the 
* See ' Kussia-in-Europe and the Ural Moun- 1850, vol. lxxivii., Article ' Siberia and California,' 
tains,' p. 437 et seq.; Trans. K. Geogr. Soc., Pre- p. 39. Quart. Journ. Geol. Soc. Lond. vol. viii. 
sident's Discourses, vol. xiv. 1844-1845, — in the p. 134. And, lastlv, ' Further Papers on the 
first of which the Australian rocks were compared Eecent Discovery of Gold in Australia,' presented 
with those of the Ural. Trans. Koyal Geological to Parliament Aug. 16, 1853, p. 43, including my 
Society, Cornwall, 1846, p. 324 et seq., in which correspondence, in 1848, with Her Majesty's Se- 
Cornish tin-miners were incited to emigrate and cretary for the Colonies, on the then known exist- 
work for gold in Australia. Eeport of the British ence of gold in Australia, and tendering my advice 
Association for the Advancement of Science, 1849 as to the manner of opening out useful gold-works 
(Trans, of Sections, p. 60). Proceedings of the in the Colony. 
Eoyal Institution, March 1850. Quarterly Review, 
