president's address. SECTION 0. 177 



gence has varied at different times — the sea alternately 

 receding and encroaching by repeated pulsations of the 

 earth's crust.* In each of these recent transgressions 

 of the sea all the included species are existing forms, 

 but there is a difference of facies between the older and 

 newer encroachments, and a few species found in the 

 older deposits are no longer occupants of our local waters. 

 The present tendency of the coast line is in the direction 

 of uplift. The earth movements, being of an oscillating 

 kind, point to the conclusion that the movements are 

 due to something more than a simple slipping-down 

 along a fault plane, and are, in part at least, the result 

 of deep-seated causes with regional effects. 

 3. The evidences establish the fact that the present aridity of 

 the climate of South Australia is also of comparatively 

 recent origin. South Australia is a land of lost rivers — 

 mighty rivers that had a perennial flow and were at all 

 times fresh. At no very distant date Central Australia 

 possessed a hydrographic connexion with the Southern 

 Ocean, and, to a large extent, must have been one of 

 the best-watered regions of Australia. The recent 

 existence in Central Australia of large herbivores, as well 

 as such aquatic animals as ceratodus, chelonians, alli- 

 gators, and other forms of fluviatile life, demands an 

 abundant rainfall and permanently flowing waters. The 

 remains of such a fauna, occurring amidst sandy deserts 

 and waterless wadies, supply convincing proofs that the 

 climate of Central and South-central Australia has changed 

 very much for the worse within recent times. This con- 

 clusion is confirmed by the fact that the existing topo- 

 graphical features stand related, not so much to the 

 present, as to an extinct system of drainage, the loss of 

 which involved the extinction of a great variety of life 

 that was dependent on such fluviatile conditions. 



4. A study of the physiographical features of South Australia 

 enables us to define the primary cause of this momentous 

 change in the evolution of the country. The develop- 

 ment of a new water-parting within a short distance of 

 the southern coast, and thereby intercepting the former 

 lines of drainage, had far-reaching effects, and supplies 

 an adequate explanation of those hydrographic and 



* " Remarks on a Geological Section at the New Graving Dock, Glanville, with Special 

 Reference to a supposed Old Land Surface now bplow Soa-level." Trans. Roy. Sec. S. Aus., 

 Vol. X, pp. 31-35. " Notes on Recurrent Transgressions of the Sea at Dry Creek." Ibid., 

 Vol. XXXVI, pp. 34-39. 



