president's address. 1229 



two above mentioned ; for as these are given from such widely 

 separated localities, we may be assured that the physical conditions 

 which they indicate prevailed also over the whole country. And 

 this is furtlier supported by the occurrence of those extensive 

 plains of the interior which have been formed by the deposition of 

 the gravels and earthy sediment washed from the hills. Reference 

 was made to this subject at one of our monthly meetings when Mr. 

 J. G. Griffin, C.E., exhibited samples of the fluviatile deposits 

 of the Riverina plains near Deniliquin. 



The rainfall of the Pleistocene period must have been consider- 

 ably greater than that of the present. 



Excepting in places where the declivity of the ground is steep, 

 or where the protecting covering of vegetation has been removed 

 by traffic of stock or artificial cuttings, allowing running water 

 access to soft earths or drifts, the tendency chiefly is for the 

 alluvial debris from the hills, not to be swept away by the running 

 streams, but to accumulate and form alluvial flats in the valleys. 

 And the highest floods now experienced, though in places, as on 

 the Darling, Murrumbidgee, and other rivers, they overflow the 

 country for many miles on either side of their ordinary channels, 

 yet they do not rise so high as to cover other portions of the great 

 plains which have clearly been formed under the flood waters of 

 tlie Pleistocene period. Mr. Russell, the Government Astronomer, 

 in his pamphlet on the " Physical Geography and Climate of 

 New South Wales," after describing the Macquarie and other 

 tributaries flowing into the Darling from the south-east, says 

 '•'Beyond all these, to the N.W., the Darling at one time must 

 have been fed by very large tributaries bringing the water from 

 tropical Queensland ; the courses of several of these can still be 

 traced to the Darling, but except in great floods they never 

 contain water and cannot now be called tributaries, There are 

 many unmistakeable proofs that the Darling was at one time 

 subject to much greater floods. In addition to these now little- 

 used wacer-courses, the banks of the river are higher than the 

 back country, and have evidently been made so by alluvial 

 deposits where floods never reach now." 



