262 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
In the New-South-Wales Catalogue of the International Exhibi- 
~~ tion, T. Dalton, Esq., remarks, on the Rocky-River district, that 
vegetable remains were found in a silicified state amongst the lowest 
strata of sand, resting upon the granites, beneath the basalt on all 
parts of this gold-field. Respecting the clays that intervene between 
the basalts and drifts of quartzose sand, he says, ‘ In some cases 
these clays alternate with sand-drifts. There is no sheet or stratum 
of clay extending over the entire Flat at any given depth beneath 
the basalts; on the contrary, they vary in colour and thickness in 
almost every claim; on the southern part of the Flat, buff, black, 
and pure white predominate. All these sands and clays appear to 
have been derived from the decomposition of the neighbouring gra- 
nites and their quartz-veins.” 
“Sydney Flat is a depression situated just beneath the basaltic 
plains that form the summit of the main range. It is bounded on 
the south by Mount Jones, and on the north by Dogherty’s Hill. 
The granite under Mount Jones crosses Sydney Flat, and, passing 
under Dogherty’s Hill, maintains a general level, with the exception 
of bars trending north or north-east, the channels between which 
are full of now soft granite, which falls to pieces at the touch.” 
I have already pointed out* that the surface of the Australian con- 
tinent appears to have been subject to great denudation, the Sydney 
Flat district being another evidence of the fact, in which thick 
drifts and dense conglomerates have to be passed through, with occa- 
sional beds of clay or marl, to reach the auriferous deposits of the 
granitic basin below; whilst these are, in their turn, covered up by 
basalts of probably Tertiary or Posttertiary age. 
It would appear, at first view, that drifts of such great thickness, 
and covering so large an area, must have been attended by pheno- 
mena altogether unfavourable to the preservation of the more deli- 
cate organisms of the period when they were deposited; but, on 
the contrary, it will be seen that not only the vegetation but the 
most fragile insect-life of the period may be found in the marls and 
clays intercalated with the auriferous drifts of the Rocky-River 
district. It is probable from this that the drifts have been depo- 
sited at varying intervals, and that there have been periods of repose 
within which the laminated marls and clays, which are associated 
with them, were slowly accumulated in the basins in which they 
are now found, whilst often these may have again been partially 
denuded by the recurrence of the phenomena which produced the 
drifts above them, and with which they are associated. 
On proceeding to examine the piece of laminated marl, I detected 
the presence of vegetable remains, and soon succeeded in opening 
up a tolerably perfect leaf, though wanting its apex, of some dicoty- 
ledonous plant. This was followed by a second leaf, belonging to 
the same order, but to a different plant; whilst a third genus is 
shown by the upper part of a flat narrow leaf, evidently allied to 
the Coniferee. The last appears to be abundant, as three or four 
examples were present, one or two of which were sufficiently well 
* Vide supra, p. 233. 
