60 T. W. E. DAVID. 



accurate gravity survey made across the rift valley of 

 South Australia, across the islands of Bass Strait, and 

 across the islands of Torres Straits and the mainland. The 

 Government Astronomer at Melbourne, Mr. Baracchi, has 

 the necessary instruments for such a survey. 



8. While, as already stated, the dominant crust creep in 

 Australia has been westerly, there has also been a tendency, 

 in accordance with the principle enunciated by Suess, for 

 subsidence areas to be overthrust, or, perhaps as others 

 state it, for the subsidence areas to underthrust adjacent 

 regions, or for overthrusting above and underthrusting 

 beneath. 



9. The wide gaps in our knowledge of the trend lines of 

 Australia emphasize the urgent need for a vastly extended 

 series of observations, both on land and sea, before any 

 satisfactory theory can be advanced as to the plan upon 

 which this island continent has been built. 1 



Acknowledgments. — In addition to those whose help has 

 already been acknowledged at the beginning of this address, 

 I desire to express my gratitude to Mr. W. S. Dun for 

 numerous references, and to JDr. W. G. Woolnough, Messrs. 

 Leo A. Cotton, b.sc, W. R. Browne, b.sc, and A. B.Walkom, 

 b.sc, for assistance in correlating trend lines. Further I am 

 much indebted to Messrs. E. C. Andrews, b.a., C. Hedley, 

 and O. A. Siissmilch, f.g.s., for much useful information in 

 the preparation of the relief model forming Plates 1 and 3. 



1 Subsequent to the reading of the above address, the following valu- 

 able papers have been published, containing much additional information 

 on the evolution of Australia : — " Physiography of Eastern Australia," 

 by T. Griffith Taylor, b.sc, b.e., b.a., f.g.s., Commonwealth Bureau of 

 Meteorology, Melbourne, Bulletin 8, May, 1911. An able summary of 

 trend lines and earth movements in areas adjacent to Australia is given 

 by Professor P. Marshall, m.a., d.sc, f.g.s., Eept. Austr. Assoc. Adv. Sci., 

 Brisbane, 1910. " Ocean Contours and Earth Movements in the South 

 West Pacific/' pp. 432 - 449, with four maps. 



