504 NEW SOUTH WALES. 
In contact with the basalt it is horizontally slivered, or broken into thin 
chips, for an inch or two, and the surface of the layer is much exca- 
vated or honeycombed. It is a striking fact that the sandstone at one 
place should have a gray colour near the middle of a cliff, though 
red above and below. In Mount Coolomgata there is red sandstone 
under the basalt, and this rests upon the usual gray rock. 
The change of colour here indicated must depend on the iron in the 
rock ; and where, under similar circumstances as to position, the heat 
has not produced it, we may infer that the iron was too sparingly 
disseminated. The distribution of heat required for the effect would 
take place readily by means of the water penetrating the rock under 
the pressure of the sea above. ‘The extent to which the necessary 
heat operated is shown by the usual thickness of the red layer. 
The reverse effect of the sandstone on the basalt is also distinct in 
some places. At Rocky Cove, the basalt, for two or three inches 
above the sandstone, breaks into small fragments as large as a walnut. 
In one of the bluffs north of Kiama, the prevailing dull grayish-green 
colour of the basalt, gradually changes to dirty olive-green six feet 
from the sandstone, and nearer the sandstone is almost black,—a 
change which may be attributable perhaps to iron from the sandstone. 
The rock, moreover, is very much fissured horizontally. Six inches 
of basaltic conglomerate separate the basalt and sandstone. 
From the facts stated, especially the occurrence of the basaltic con- 
olomerate with the basalt, and this graduating into the sandstone, it 
is evident that the basaltic beds were overflowings of the rock in 
fusion before the upper sandstone layers were deposited, and were 
not the result of intrusion. The same conclusion is deduced from 
the red colour of much of the sandstone below the basalt, and the 
breaking of it immediately adjacent. The occurrence also of peb- 
bles and masses of basalt in the Wollongong rock indicates the exis- 
tence of other beds of still earlier age, though probably of the same 
epoch. 
A few narrow seams of baked conglomerate occur in basalt at an 
elevation of one thousand two hundred feet on the Illawarra range, 
just to the south of Broughton’s Head, on the road leading from the 
Kangaroo Grounds. The surface of the basalt was exposed for a few 
square yards, and through it run irregular seams half an inch to three 
inches wide, which were filled with this conglomerate. The seams 
appeared to occupy fissures produced by contraction on cooling; but 
when or how filled and baked, we could not conjecture, without a 
