284
PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .April 9,
The coal- shales of the Hunter River district are full of fossil
leaves, and some of them consist of a mixture of coal and clay, and
contam such an amount of hituminous matter that Mr. Beaumont
(Mineralogist to the Australian Agricultural Company) has expressed
an opinion that gas might be manufactured from them. Two seams
of coal only are being worked in this district ; a third is known to
exist, but is supposed to be too thin to pay for working at present.
It is two feet thick where seen, and is situated considerably below
the sea-level. The other two seams are from four to six feet thick,
but contain seams of carbonaceous shale which deteriorate the quality
of the coal.
At the entrance of Newcastle Harbour is a perpendicular rock
(called Nobby' s Island), once separated from the main land, but
now united by a breakwater that has been thrown across for the
protection of the harbour. The island exhibits a good section of
the rocks of the coal-field. The accompanying section shows the
arrangement of the strata.
Section of Nobby^s Island, Newcastle Harbour,
1. Mould.
2. Trap-conglomerate.
3. Shales with plant-remains.
4. Coal.
5. Earthy sandstones and shales.
6. Chert.
7. Imperfect sandstones and shales.
8. Coal.
9. Trap-dyke.
The island is intersected by a trap-dyke, 9 feet thick, running in
a direction nearly S.E. and N.W., and completely decomposed from
the top down to the sea-level, presenting only a greenish-white
greasy clay ; but beneath the water the dyke is perfectly sound and
hard ; about low-water-level it crops up through the beach, and may
be seen at some little distance running out into the sea. A bed of
coal (the second in the series), that formerly extended far beyond the
present limits of the island, and through which the dyke passes, has
been washed away by the waves, with the exception of a few feet on