BAS AMNIC AND ALL BD ‘ROCKS. 499 
a dirty black to a dirty green, and the feldspar crystals have usually 
the latter colour. The porphyritic rock of Keelhogue passes into the 
amygdaloid of the same region (K). 
Position of the Basalt—The basaltic rock occurs both in layers in- 
terstratified with sandstone, and in dikes. By its occurrence, both 
underlying some layers below the coal, and also protruding through 
the Sydney sandstone, it appears to be of different ages. 
In Layers alternating with Sandstone.—The alternation of sandstone 
and basalt may be seen in many of the cliffs from Black Head to 
Point Bass, six miles north of Kiama, as shown in the line of cliffs 
represented on the map of New South Wales. At Black Head, the 
basalt does not occur in the cliff itself, but may be seen overlying the 
argillaceous sandstone a few hundred yards back. Going to the 
northward from this cape, the basalt soon appears capping the bluffs, 
and dipping with the sandstone below to the northward and west- 
ward. ‘This layer of basalt, farther north, dips to the water just north 
of Stony Cove, three miles south of Kiama, where the lower sandstone 
layer is no longer in sight. ‘The next bluff north is wholly basaltic. 
The next beyond is capped with red sandstone; this rock does not 
appear on the following cliff (at Kiama), which is very low, but com- 
poses the whole of the next one, with the exception of a small basaltic 
portion near the water’s surface at the south end. The basalt thus 
dips beneath the water like the layer of sandstone before mentioned. 
Continuing our course northward, in the next cliff, the sandstone be- 
comes capped with a second layer of basalt. Farther on, the sand- 
stone disappears, and leaves the basalt alone. 
There are hence, in this coast section, two distinct layers of sand- 
stone, and two of basalt interstratified with them; and they disappear 
in succession as we go northward from Black Head, excepting the 
upper basalt. The following is a general view of them, with the 
thickness of each. 
Upper basalt, - - - - - 80 feet. 
Red sandstone, - = 2 - - - 60 « 
Second layer of basalt, - - - - 100 «“ 
Blue argillaceous sandstone of Wollongong and Black Head, 
150 feet thick in Coolomgata,. 
The first of the following figures represents the north cliff of Gerin- 
gong Boat Harbour, and the second the corresponding one on the 
