1118 The Geology of Central Australia, [ November, 3 
pressed interior. The highest border is on the east, facing the 
largest ocean, and it averages about 2000 feet in height. The 
south side is either level with the ocean or abuts upon it in cliffs 
varying from 300 to 600 feet in height. The western is about 
1000 feet above the sea, and the northern a little higher, Aus 
tralia is thus in the form of an immense table-land. The seaward 
side is generally precipitous, but narrow tracts of lowland some 
times intervene between the elevated region and the sea. The. 
continent slopes gradually inland from the elevated borders to the 
central depression at Lake Eyre, which is south-east of the topo- 
graphical center. The main cordillera of the continent forms the 
eastern border. It consists essentially of a central granitic axis 
with doleritic or dioritic dykes flanked by highly inclined Arch- 
æan and Silurian schists, Devonian rocks less inclined and altered, 
and the upper and lower coal measures. Over these lie the al- 
most horizontal beds of the Hawkesbury series (Lower Meso- A 
zoic). It is generally conceded that this cordillera is of Palao- 
zoic age, and was elevated at the close of that period. 
western border, as far as is known, resembles the eastern. ae 
Throughout the table-land are various isolated mountat — 
ranges which do not extend for any distance. These range 
trend either nearly north and south or east and west. The largest 4 
of them is the Flinders, which begins at Cape Jervis on the south 4 
coast and extends to the south end of the Lake Eyre basi re T 
it ends abruptly. West of Lake Eyre is a chain trending we : 
north-north-east, consisting of two ranges, the Peake and 
Margaret. North-west of these, on the 26th parallel, 1S pict 
range, the Musgrave, which trends about east-north-east. + ihe 
of this is another, the MacDonald, parallel to it. These are’ a 
main ranges, but isolated mountains of granitic base crop out a 
various places. eee 
The south side of the continent is formed, with but little i ] 
ruption, by a series of Tertiary rocks, representing probei 
the formations from the Eocene upwards. They °x 
ste sea it : 
the Australian Bight are Miocene. The Murray Rivet 
also formed by Tertiary rocks of various formations. — . 
eastern and south-eastern coasts these deposits are overl; : from q 
by volcanic emanations or by sands, clays and marls rel: spi 
the sub-aérial weathering of the Paleozoic rocks. “°°” 
