460 
SILURIA. 
[Chap. XIX. 
As the phenomena described are common to many countries, the accompany- 
ing diagram is annexed, to convey, as far as possible at one view, a popular idea 
of the chief conditions under which gold has been formed and afterwards distri- 
buted over the surface, so as to be profitably collected by mankind. At the same 
time, it is not to be accepted as an accurate view of the relations of the vein- 
stones to the strata in which they occur. 
Ideal Representation op Gold as formed in Veinstones in Original Rocks, 
and its subsequent transport into heaps of debris. 
a. Slaty rocks : the metamorphosed Pakeozoic rocks, chiefly of Lower-Silurian age, 
now in the condition of talcose, micaceous, chloritic, felspathic, or siliceous slates, tra- 
versed by igneous auriferous rocks (b) and auriferous veinstones, chiefly quartzose, c. 
Above their present dark-lined summits is seen a more lightly tinted outline (d), 
which represents the condition of the auriferous ridges before their former tops were 
subjected to abrasion, by which great heaps of drifted gravel (e, e) were transported 
from them, covering the adjacent slopes and filling up the gorges and depressions. 
The highest of these Drifts constitute the ' dry diggings ' of the miner, — the lower 
heaps, in which streams meander, being the ' wet diggings.' As it is impossible to 
represent in one diagram all the conditions under which gold was originally formed in 
the rocks, I have merely selected the usual case of veinstones (c), the higher (de- 
stroyed) portions of which were richer than the veinstones deep in the solid rock. 
Gold of Australia. — The extraordinary quantity of gold which has been poured 
into Britain from her Australian Colonies during the last few years has been 
chiefly procured, like most of the gold in the other tracts described, from super- 
ficial accumulations of shingle, gravel, sand, and clay, derived from the wearing 
away of adjacent hard rocks, whether of aqueous or of igneous origin. 
Having, in the year 1844, recently returned from the auriferous Ural Moun- 
tains, I had the advantage of examining the numerous specimens collected by 
my friend Count Strzelecki along the eastern chain of Australia. Seeing the 
great similarity of the rocks of those two distant countries, I had little difficulty 
in drawing a parallel between them ; in doing which I was naturally struck by 
the circumstance that no gold "had yet been found " in the meridional Austra- 
lian ridge, which in anticipation I termed the ' Cordillera ' *. Impressed with 
the subsequent operations having been paralyzed 
chiefly by the political revolutions which have oc- 
curred in those countries. If the former trials of 
Spaniards to procure gold with profit from deep 
mines in the solid rock, and which were proverbi- 
ally failures, do not satisfy living speculators, let 
me refer them to similar results in our day, and 
trials by our own countrymen. Among these, I 
would specially allude to the well-known mine of 
G-uadalupe y Calvo, near Durango in Mexico, 
worked by British skill and capital, where, accord- 
ing to information I received from one of its ablest 
directors (my friend the late Col. Colquhoun, 
E.A.), the works, which afforded a moderate profit 
near the surface, became less productive as the 
mine deepened, and finally failed altogether — the 
gold having thinned out, and its place being en- 
tirely taken by argentiferous galena. See Quar- 
terly Review, art. 4 Siberia and California,' vol. 
lxxxvii. p. 410. 
* The announcement that "no gold had yet 
been detected," which was printed in my Presi- 
dential Discourse, Trans. Eoy. Geogr. Soc. 1844, is 
the clearest proof of my ignorance of a trace of 
the metal having been discovered by any one. 
Some time after the practical opening out of the 
gold mines, however, facts transpired which were 
totally unknown to me when I ventured upon my 
comparison. Thus it appeared that Count Strze- 
lecki himself discovered traces of gold in 1839; 
but, on relating the fact to some friends and to 
the G-overnor of New South Wales, Sir G-. Gipps, 
secrecy was enjoined, and the Count never more 
reverted to the subject, not even in his own work 
