8 Coal Basin of New South Wales. 
denudation of silurian rocks, or of their contained quartz 
veins, could possibly take place ; and the miocene rocks 
generally bear strong evidence of being derived rather from 
the mesozoic—that is, the carboniferous shales and sand- 
stones, than from the older rocks. The pliocene beds, on the 
other hand, contain the refuse of silurian rocks in great | 
abundance. Hence the non-auriferous character of the 
former, and the rich gold deposits found exclusively in the 
latter. You cannot very well divest a man of his shirt 
whilst he is still wrapped up in his overcoat. The older 
rocks of Victoria probably enjoyed an immunity from 
denudation in the miocene period from a somewhat similar 
reason ; they were at that time covered to a thickness of 
many hundred feet by the lower mesozoic and the upper 
palzeozoic deposits. I put forward this bit of theorizing 
with the utmost diffidence—a diffidence which would be 
still greater only that I find my own views upon the subject 
are identical with those of more than one geologist, whose 
acquaintance with Victorian strata is by no means con- 
temptible. 
But then again it must be conceded that there are some 
few places, as on the beach near St. Kilda, where patches of 
what seem to be miocene repose immediately upon silurian 
strata—a fact somewhat militating the theory just laid 
down of the older rocks being covered by carboniferous beds 
during the earlier tertiary period. 
I trust that this attempt to illustrate a fact in Victorian 
geology, by the phenomena observed in an adjacent colony, 
will not be deemed an unpardonable digression. I trust. 
also that I have stated the case with all fairness, for I assure 
you that, equally with Mr. Selwyn and your Society, 1 am 
only desirous of eliciting the truth. 
DENUDATION. 
I come, in the last place, to what is perhaps the most 
interesting feature of the sandstone formation of New South 
Wales—viz., the very remarkable manner in which the 
strata have been worn into deep valleys and gorges, pre- 
senting phenomena unparalleled in any other portion of the 
world. 
The denudation that has taken place near Newcastle, 
where the surface has been literally planed down by aqueous 
agency, presents but few difficulties. The phenomena wit- 
