130 
Geology and Physical Geography ; 
2. River, Creek, and Gully Workings. — The deposits of gravel, 
drift, &c., resting on the Silurian rocks in the bods or on the banks 
of -water-courses. These deposits vary from a few inches to 
many feet in thickness ; the gold is usually found low down in the 
gravel, on the bed-rock or deep in its crevices; in river valleys, 
terraces of auriferous gravel are sometimes met with on the rocky 
slopes high above the river beds. These appear to he vestiges of 
deposits formed before the water-courses had eroded their channels 
to so groat a depth in the bed-rock as they have since reached. 
The gold in all these deposits has been either derived directly 
from the disintegration of the qiiartziferous Silurian rocks, or 
from the denudation and re-distribution of pre-existing drifts. 
3. Leads. — Gravels, conglomerates, &c., of Middle or Upper 
Tertiary age, deposited in the beds of ancient rivers, in some places 
only covered by recent accumulations, and in others by one, two, 
three, or four distinct layers of basalt. To such may bo added 
some “ reef-washes,” which have been formed during intervals 
between the outpouring of two different lava-flows. The beds of 
these ancient rivers are in some localities above, and in others 
below, those of existing streams, and are worked by tunnels or 
shafts accordingly. 
4. Gravels, conglomerates, &c., apparently duo to marine 
littoral action ; these are generally more -widely spread than the 
lead gravels ; the gold is more “patchy* in its occurrence, though 
sometimes found in defined “runs,” not necessarily in the deepest 
hollows of the bed-rock, but often on the ridges or slopes thereof. 
Some of these deposits cap hills of Silurian rock ; others consti- 
tute “ reef-washes ” beneath the basalt, but at higher levels than 
the deep lead gutters. Though the above embrace the chief forms 
of auriferous alluvial deposits, there is an infinite variety of 
combinations to he met with, but all attributable to the same prin- 
cipal cause — denudation by atmospheric aiul aqueous action of the 
Silurian rocks and their accompanying quartz-veins. It is not to 
be supposed, however, that all our alluvial gold was disintegrated 
from its matrices only since the commencement of Tertiary times. 
We have such irrefragable proof that denunciation has been acting 
on the Silurian rocks from their first appearance as a land surface, 
that it is only reasonable to believe that considerable proportions 
of the gold found in, and the materials composing, the various 
auriferous gravels, w ere disintegrated from the matrices and rock- 
masses during Upper Palaeozoic and Mesozoic times. 
The water-worn character of the pebbles and boulders, and also 
the gold itself in the gravels quite close to the apparent sources 
whence their materials were derived, indicate that the fragments 
were broken from the rocks and rounded by forces acting prior to 
the agencies which finally deposited the gravels, and that these 
are for a great part re-distributions of pre-existing deposits 
