Chap. XIX.] 
GOLD OF AUSTRALIA. 
463 
terrestrial surfaces, at periods posterior to those powerful subaqueous abrasions 
of the rocks which formed the chief masses of Drift *. Just as in the Ural 
Mountains (p. 456), these gold-drifts of Victoria, like others described by Mr. 
Clarke in New South Wales, contain the bones of extinct species of quadrupeds f : 
in these latter cases, however, the animals are peculiar to the Australian con- 
tinent. 
By consulting Mr. Selwyn's Reports, it will be found that he refers, as above 
stated, the auriferous Drifts to three periods of time, two of which he con- 
siders to be of Tertiary age, and the most recent of modern date and alluvial 
action. At first sight the reader might suppose that these data are in opposition 
to my previous statement, that Secondary and Tertiary rocks per se have not fur- 
nished gold ; but such is not the case ; for all I assert, particularly in re- 
ference to Australia, is, that no veinstones or original segregations of gold worthy 
of notice have been found in such Secondary or Tertiary rocks (certainly 
where they are unaltered), but are chiefly confined to the Palaeozoic rocks, and 
especially to the Silurian and their associated igneous masses. The gold-drift 
which most prevails in Siberia, as in many other countries, is truly a Post- 
pliocene accumulation, being charged with the remains of extinct Mammalia. 
The data, however, which are here contributed by the researches of Mr. Selwyn 
are new to geologists, since they appear to indicate that one of the gold-drifts of 
Victoria is of Miocene age. Still it was one of those Drifts by the medium of 
which the gold was abstracted (by what I conceive to have been a powerful de- 
nudation) from the parent rock, just as in the subsequent or Post-pliocene time. 
The peculiar features of the successive distribution of the auriferous Drifts of 
Victoria are well explained by Mr. Selwyn J, and have been beautifully illus- 
trated in his coloured maps and diagrams. 
The observations of Mr. John Phillips, a gentleman who, in the year 1847, 
called my attention to the existence of traces of gold in South Australia (in ac- 
cordance with my hypothesis), agree generally with those of Mr. Selwyn re- 
specting the rich detrital accumulations §. 
The local character of the gold-accumulation of the large Peel-River tract of 
Australia was closely examined by Mr. Odernheimer, who, uniting the practical 
habits of a German miner with an intimate knowledge of mineralogy, has shown 
that there the gold occurs in small quantities only. The thin auriferous quartz - 
veins lie usually in diorite; and he holds the opinion that the gold results 
from the decomposition of auriferous iron-pyrites diffused through hornblende- 
rock, syenite, porphyry, and breccia, as well as diorite. Chromate of iron, 
hematite, and magnetic iron-ore, as well as several precious stones, have been 
recognized in that region ||. 
that region to the Geological Society of London. 
From his own observation and experience he af- 
firmed the fact of the downward impoverishment 
of gold-bearing quartz -veins, and he demonstrated 
that the richest produce is essentially derived from 
loose superficial de'bris. 
* In addition to his determination of the age of 
the original gold-bearing rocks, and the three 
derivative sediments into which he divides their 
detritus in Victoria, Mr. Selwyn thus writes to 
Prof. Eamsay : — " A somewhat remarkable fact, in 
connexion with nearly all the great granitic 
masses which I have examined, is that, although 
they invariably alter the slate-rocks near their 
junction and send veins into them, they do not in 
the slightest degree affect the general strike or 
dip of those beds, but appear to have themselves 
partaken of the movements which placed those 
Silurian strata in their highly inclined and con- 
torted positions, and gave them their very uniform 
meridional direction." He adds, " There is very 
little slaty cleavage till we get low down into the 
Llandeilo beds." 
t See Eev. W. B. Clarke, Quart. Journ. Geol. 
Soc. vol. xi. p. 405, where much information is 
brought together by the author. 
I See Quart. J ourn. Geol. Soc. vol. x. p. 299 ; 
vol. xiv. p. 533. 
§ See also Eosales on gold-drift below basalt, 
&c, Quart. Journ. Geol. Soc. vol. xi. p. 397, also 
the vol. xiv., including valuable notes and me- 
moirs by Mr. Selwyn, Mr. Phillips, Mr. Eedaway, 
and Mr. Eosales. 
|| See Quart. Journ. Geol. Soc. vol. xi. p. 399 ; 
and vol. xii. p. 287 ; also a paper on Australian 
Gems, by Mr. G. M. Stephen, ibid. vol. x. p. 303. 
