516 NEW SOUTH WALES. 
feet of earth of the same origin, having a brownish-black colour, and 
this is covered again by four feet of brownish-red soil. 
The syenitic basalt of the more distant portions of Prospect Hill is 
also very decomposable. It forms a brownish-yellow bed, spotted with 
decomposing crystals of augite. 
Siliceous concretions have often been observed to result from the 
decomposition of basaltic rocks; and I would attribute to this source a 
deposit of this nature occurring in the soil of the plains at the foot of 
Prospect Hill, five miles west of Paramatta, where it was pointed out 
to the writer by the Rev. W. B. Clarke, well known for his geological 
researches. ‘There are four or five layers in a section of the soil border- 
ing a small brook, alternating with the common earthy material of the 
soil; the uppermost was within twenty inches of the surface. The 
concretions are in irregular nodules, varying from the size of a hazel- 
nut to that of the fist, though in the same layer nearly uniform. 
They consist of clay concreted by silica, and have a white or grayish- 
white colour. The basalt of Prospect Hill consists largely of feldspar, 
and as it is undergoing decomposition, silica is liberated, and taken up 
by the waters, again to be deposited in the soil of the plains below. 
This deposition would necessarily take place in those layers of the soil 
which were the most compact or clayey. 
VI. CIRCUMSTANCES ATTENDING THE ORIGIN OF 
THE DEPOSITS. 
There are several striking facts in the nature and condition of the 
rocks we have described which give us some insight into the early 
history of New Holland. The first particulars that we observe are as 
follows :— 
a. The layers below the coal abound in animal fossils, and contain 
but few traces of vegetable remains. 
b. 'The coal series is profuse in vegetable remains, and offers rarely a 
species of animal. A single fish is all we are acquainted with. 
c. The layers above the coal (the Sydney sandstone series) contain 
but few traces of vegetable remains, and none of animal. 
There was therefore a disappearance of marine animal life in the 
region, after the lower layers were deposited, and a comparative ab- 
sence of vegetation after the deposition of the coal layers. 
The character of the argillaceous sandstones below the coal, and the 
