462 
SILURIA. 
[Chap. XIX. 
heaps of debris, or old alluvia, derived chiefly from veinstones in old slaty rocks, 
and often adjacent to or associated with eruptive rocks, whether granites, por- 
phyries, or greenstones. I also assumed that the chief auriferous slaty rocks of 
Eastern Australia are of the same age as the central masses of the Ural, viz. * 
Lower-Silurian, because, like them, they are overlain in parts by strata which 
contain Pentameri, Trilobites, and Corals, indicative of the Upper Silurian group. 
Many of these last have been identified by my friend Mr. Lonsdale, who con- 
siders some to be Upper Silurian, and others referable to the Carboniferous era. 
The shells, examined by Mr. Salter, confirm this conclusion ; and the Carbonife- 
rous strata, with European forms of life, appear to be clearly separable from the 
Devonian. Indeed the Lower Palaeozoic rocks are here followed by Devonian 
and Carboniferous strata. 
Whilst the most prolific sources in Australia seem to have been the quartzose 
veinstones which traverse the Silurian slaty rocks, we are further instructed that, 
as in the Ural Mountains, there are tracts wherein gold is diffused in small 
particles through the body of granitic rocks *, especially those (according to Mr. 
Clarke) which are hornblendic or syenitic : the limestones, however, in both 
countries are partially auriferous only. There is, besides, this striking coinci- 
dence between Australia and the Ural : both chains have a main meridional 
direction, the strike of the old slaty rocks and also of the chief gold-veins being 
from north to south. 
In respect to Victoria, which, of all the Australian Colonies, has proved to be 
much the most productive of gold f> the age of the slaty rocks containing the 
auriferous veins has been still more clearly determined. Mr. Alfred Selwyn J, 
the Director of the Geological Survey of the Colony, cites the occurrence of nu- 
merous Silurian fossils, including Trilobites, Graptolites (Didymograpsus &c), 
and Lingulse, as described by Professor M'Coy. Mr. Selwyn has further re- 
cognized, in Victoria, gold-bearing superficial Drifts of three distinct stages, 
lying above each other, the lowest or oldest of them containing the remains of 
wood and seed-vessels differing little from the present vegetation. Even the cones 
of the Banksia, a tree still prevalent in Australia, have been brought home by 
Mr. Redaway from one of the bottom Drifts, and, being examined at my request, 
identified as such by the illustrious botanist the late Robert Brown, who first 
discovered and named the genus. A local distinction in these Tertiary gold-drifts 
or detrital beds of Victoria is, that they have been overflowed and even interlaced 
by basaltic coulees, which evidently proceeded from terrestrial volcanos, inas- 
much as the vegetable matter beneath them has been charred and destroyed in 
situ by the eruption. This phenomenon, first adverted to by Mr. Selwyn and Mr. 
H. Rosales, exhibits a strong analogy to what is seen in California §, Mexico, and 
South America. In all these countries igneous eruptions have burst forth on 
tains, and to my prediction respecting the auri- 
ferous character of the Australian rocks. At the 
first Anniversary Dinner of the Australian Colo- 
nists from New South Wales, Victoria, South and 
West Austra^a, and Tasmania, which took place 
on the 26th of January 18n8, Sir Charles Nicholson, 
formerly Speaker of the House of Representatives, 
and also the head of the University of Sydney, 
asserted, from the Chair, that his brother-colonists 
agreed with him in the sentiments he expressed ; 
and this opinion he repeated at a public meeting 
in the Town Hall of Leeds, on the 29th of Sep- 
tember 1858. 
* See ' Russia and the Ural Mountains,' vol. i. 
p. 483, where it is stated, " The fact is, then, that 
though gold has frequently been, and is for the 
most part formed in quartzose and other veins 
which have either penetrated or been separated 
from the mass of the slate formation (and of these 
the Ural affords countless examples), it has also 
been diffused in some tracts throughout the whole 
body of the rock, whether of igneous or of aqueous 
origin." 
t One of the earliest notices of the gold-fields 
of Victoria is by Mr. &. H. Wathen, in the Quart. 
Journ. G-eol. Soc. vol. ix. p. 74. 
I See a reference to the successful labours of 
this geologist in North Wales, p. 82. 
§ Mr. J. S. Wilson, who, after a residence in 
South Australia, passed three years as a gold- 
miner in the Sierra Nevada of California, com- 
municated a memoir on the auriferous rocks of 
