PRESIDENTIAL ADDRESS. 19 
profitable to consider the division in which Australia occurs, 
namely, the south western portion, inasmuch as it falls 
properly within the Australian sphere. 
It is here proposed to mention merely the general arrange- 
ment of the main topographical features together with 
their age. 
(1) Disposal of Topographical Forms.—The main topo- 
graphical features of the region under discussion have an 
orderly arrangement, considered from the south west of 
Australia both to the Society Islands and to Micronesia. 
South Western Australia consists of a low and uniform 
plateau of great area! rising to a height of 2000 to 4000 
feet to the north and the north-east. The surface of this 
great plateau is regular and not broken by important radial 
gaps of a structural origin. 
The vast area lying between the Western Australian 
and the Hastern Australian plateaus consists of two well 
marked portions, namely, a western one of plains diversified 
by high and narrow plateau belts with warped and faulted 
margins, and an eastern one comprising the plains over- 
lying the great Australian Artesian Basin (650,000 square 
miles),and the Riverina, together with the Victorian Basin. 
The general trend of these features is curvilinear and sub- 
parallel to the plateaus associated with them to the Hast 
and West. 
The eastern margin of Australia forms another great 
geographical unit, in the shape of a plateau which is rela- 
tively narrow and high as compared with the Western 
Australian form and which is broken by low tectonic gaps 
arranged radially from a broad centre in South Western 
Australia. Bass’ Straits is the most pronounced of these 
* Jutson, J. T. Physiography of Western Australia, Geol. Sur. W.A., 
1917. 
