GEOLOGICAL STRUCTURE. 457 
These were the only rocks of sedimentary origin examined by the 
writer; and they are the predominating rocks of the country. Clay 
slates, and limestones of older formation, with granitic and allied rocks, 
have been mentioned as occurring in some parts, especially about and 
beyond the Dividing range, and south towards the Australian Alps.* 
The igneous rocks which have come under observation are basalts 
or greenstone, of several varieties, including syenitic, porphyritic, and 
amygdaloidal basalt. ‘'hese rocks occur of all ages corresponding 
with the eras of the above sedimentary rocks, or are even anterior to 
all of them; and some may be of more recent date. 
In the following pages, we may first consider the sedimentary de- 
posits, commencing with the uppermost, dwelling in detail on their 
mineral characters and stratification, their structure, fossils and im- 
bedded minerals, which particulars comprise the original peculiarities 
of the rocks; and afterwards on the changes they have subsequently 
* We add a few facts with regard to the rocks of other parts of Australia, derived 
more especially from the accounts by Fitton, (Phil. Mag. xviii. 135,) Strzelecki (N. 8, 
Wales and Van Diemen’s Land), and J. B, Jukes, (Rep. Brit. Assoc. for 1847, p. 68.) 
North of Cape Melville, on the northeast coast, the country consists mostly of porphyritic, 
feldspathic and quartzose rocks, with basalt or trap and some granite. From Cape Mel- 
ville southward nearly to the East Cape, the prevailing rock is granite, with some talcose 
slate, and serpentine. At Port Bowen, in latitude 22° 30’, there are schists, porphyries 
and basalt; and near Port Curtis, a degree farther south, syenite and red sandstone are 
said to occur. On the southeast coast, there are paleeozoic schists and sandstones, with 
granites, mica and argillaceous slates in the mountains. Mount Kosciusko, six thousand 
five hundred feet high, consists of granite, with mica slates and siliceous and argillaceous 
slates in a vertical position. Van Diemen’s Land contains granites, syenites, mica slates, 
serpentine, quartz rock, paleozoic limestones, shales and sandstones, and the coal forma- 
tion; also basalt, showing magnificent displays of columns, in many places. In the 
district of Port Philip, there is coal at Western Port. The Grampians, four thousand 
feet high, consist of the Sydney sandstone; and south, there is a tract of volcanoes. 
From Port Philip to the Murray, tertiary covers the country along the sea. About Ade- 
laide, Cape Jervis, in South Australia, there are mica slate, gneiss, clay slate and chlorite 
slate ; and in the various ranges, veins of copper and lead abound, ‘Tertiary and sand- 
stone extend westward over the country bordering the Great Bight. At King George’s 
Sound, in this same tertiary, there are ramified concretions, formerly taken for corals, 
Granite occurs in the mountains to the north; but along the shores, from the Southwest 
Cape to Shark’s Bay and beyond, the same tertiary beds are found. About the northern 
shores, east and west of Cambridge Gulf, the rock is a red ferruginous sandstone, in hori- 
zontal layers, apparently the same as the Sydney rock. A sandstone of similar cha- 
racters, but of unascertained age, occurs around the Gulf of Carpentaria. This rock has 
been supposed to be tertiary, and to extend over Central Australia. 
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