462 NEW SOUTH WALES. 
The argillaceous deposits, though generally thin, (being often but 
a few inches, and of little lateral extent,) are also at times largely 
developed. On the river opposite Paramatta, there is a perpendicular 
bank, one hundred and ten feet thick, resting on the sandstone which 
crops out below, a short distance up the stream. ‘The upper portion 
of the bed shows a gradual passage vertically into the sandstone layers, 
as it changes the blue-black colour for a whitish sandy tint several 
feet from the top, and becomes less perfectly schistose and more are- 
naceous. A similar bed occurs along the road two miles south of 
Appin. The rock is white and crumbling, resembling the upper 
portion of the deposit at Paramatta. In a section of this formation 
at the waterfall of two hundred and fifty feet, visited on the elevated 
plain between Illawarra and the Kangaroo Grounds, (page 451,) a 
similar argillaceous layer, about thirty feet thick, lies below twenty- 
five feet of sandstone; and the same is seen seven miles beyond, on 
the descent of the mountain into the Kangaroo Valley. We have no 
reason to believe that these different beds are in any way connected, 
excepting possibly those of the two last-mentioned localities. 
Structure.—The layers of sandstone average eight feet in thickness, 
but vary much even at short intervals. ‘Iwo layers, quite distinct 
from one another, unite so as to leave no trace of their former line of 
separation. Again, a new place of disjunction appears a foot or so 
above the other, and after running on for a few rods loses itself in the 
sandstone layer. ‘This remarkable irregularity, which is exhibited 
even in the subordinate parts of a layer, may be seen at any of the 
quarries or in exposed natural sections. ‘The annexed figure repre- 
sents a section on the borders of a cove half a mile east from Port 
Jackson, near the bathing houses. The layers are constituted as 
follows :— 
A. 10 feet.—Grayish-white sandstone, in part clouded with red; layers of deposition 
thin. Increases in width to the right encroaching on that below. 
