246 
Geology of Sydney. 
McKeown’s Creek, but they do not stand out as 
we see them oftentimes in limestones. They show 
merely a dull white outline on the very dark surface 
of the rock. By following the bed of any stream 
that enters McKeown’s Creek, on one’s left going 
up stream, black radiolarian cherts will be found. 
It is hardly necessary to say that the radiolaria 
or radiolarian casts can only be detected on slicing 
the rock for the microscope. Generally, the radio- 
larian cherts occur to the west of Cave House. 
(4.) White marble limestone can be found about a 
mile-and-a-half down the Cave River. 
(5.) Basalt of Tertiary age is found covering hilltops 
more than two thousand feet above the Caves. 
The excavation of all the great valleys around was 
certainly subsequent to the eruption of this basalt. 
It has already been stated that folded and 
vertical strata may be noted in the cuttings coming 
down Cave Hill. One fold can be seen on the Cave Hill 
side of the Grand Archway. This, it will be noticed, 
is faulted. The second can be observed between here 
and InchmaiTs Creek, and portions of another fold 
are exposed about three-quarters of a mile on the 
Cave side at Pheasant’s Nest Creek. 
The belt of limestone in which the Caves occur 
measures about three hundred yards across, and runs 
in a general north and south direction, striking a 
little to the west. Standing on any one of the 
higher points of the ridge, the limestone can be 
distinguished even at a distance, as it contrasts 
markedly with the surrounding Silurian slates. The 
