PRSIDENTIAL ADDRESS. 57 



the old Divide to the east of Cairns was hereby sunk 

 beneath the sea, leaving merely the sources of the rivers 

 perched high up on the top side of the fault scarp as is the 

 case with the Barron River at the Barron Falls. Profound 

 fractures like those of Broadsound and Curtis Island are 

 ample proof of the heavy crust foundering in this area. 

 The Snowy-Murrumbidgee Rift, and the faults on either side 

 of the Main Divide in New South Wales and Victoria, on 

 the whole tend to throw down the crust on either side of 

 the main axis of elevation. The fact that the old trough 

 of the great coal-field, so long a sinking region, was warped 

 up before the end of Tertiary time, suggests, that, on the 

 isostatic theory of crustal equilibrium, compensation had 

 by this time been established. At the same time the fact 

 must not be overlooked that in Post-Tertiary time the 

 dominant movement along the east coast of Australia has 

 been one of submergence rather than emergence, the sub- 

 mergence amounting to fully 200 feet. Bass Strait was 

 formed by further sag of the E. to W. trough, and develop- 

 ment of the Bacchus Marsh and Point Nepean etc. E. to 

 W. faults. 



Another great subsidence area developed itself west of 

 the Mount Lofty Range near Adelaide, trending northwards 

 through St. Vincent and Spencer Gulfs to the Lakes Torrens 

 and Eyre regions. This downward warping in the Lake 

 Eyre neighbourhood was probably preceded by a slight tilt 

 of the Cretaceous basin from N. to S., which started the 

 Darling River on its S.W. course : in Cretaceous time the 

 drainage from the N.W. part of New South Wales had gone 

 to the N.W. The 'boathook' junction of the Macquarie, 

 Castlereagh etc. rivers with the Darling is proof of this 

 reversal of the drainage in Post-Cretaceous time. 



The interesting case recorded by Mr. Charles Hedley 1 

 of an extensive change in the position of the Continental 



1 Proc. Linn. Soc. N.S. Wales, Vol. xxxvi, pt. 1, pp. 17 and 18. 



