a 
402 . W. E. DAVID, W. F. SMEETH, AND J. A. WATT. 
by the sedimentary rocks, which it has intruded. No distinct 
evidence however was obtained to prove that the eruptive rock 
was shut off in every direction by sedimentary rock, and it is 
probable that it is prolonged in the form of tongue-like apophyses 
or as dykes, in one or more directions. This supposition is con- 
firmed by the statement made to us by a local observer to the 
effect that at a distance of about one and a-half miles from the 
Pennant Hills Quarry a rock occurred, which he considered similar 
to the chromite-bearing rock, which forms the subject of this 
paper. The sedimentary rocks seen at the quarry belong to the 
Wianamatta Shales, the uppermost division of the Hawkesbury 
Series, and are admitted to be probably of Triassic Age. The 
junction line however of the under surface of the Wianamatta 
Shale with the top of the underlying Hawkesbury Sandstone 
cannot be far below the level of the bottom of the quarry, as a 
comparison of the latter level with that of the junction line 
between these two formations, as seen in the neighbouring road 
cuttings proves. It is possible that the deepest portion of this 
quarry is already below the junction line of the Wianamatta Shale 
with the Hawkesbury Sandstone, but as this portion of the quarry 
is situated wholly in the eruptive rock, this question cannot be 
settled at present. The section on the east side of the quarry 
shows that the eruptive mass of basalt has distinctly intruded the 
Wianamatta Shales, the line of junction between the two rocks 
being almost invariably characterised by the presence of a “crush- 
breccia,” composed of angular fragments of Wianamatta Shale, 
bleached to a light grey colour, and otherwise altered by the dark 
grey to black eruptive rock, in which they are imbedded. 
In addition to the angular fragments of Wianamatta Shale, 
forming the crush-breccias, there are numerous enclosures in the 
basalt (upon the eastern and south-eastern faces of the quarry), 
of other rocks, including lumps of clay shale, pieces of Hawkes- 
bury Sandstone conyerted into quartzite, and two varieties of 
eruptive rocks, both of which are foreign to the district, and one 
of which at least is not known to occur elsewhere in New South 
