On the physiograpby of Northeastern Ausfcralia. 13 



Mr. Hedley himself is of the opinion that in the tinie of the 

 tertiary peneplain the continent extended further to the east than 

 now and that the rivers had in that stage naturally a slighter slope 

 than now, „of necessity the peneplain-rivers were longer, slower, and 

 straighter than these (présent marginal rivers). They had no fall to 

 waste in that long journey to the sea. On a peneplain, circuitous 

 courses would mean final stagnation." 



Cau such rivers with a very slight slope possess so much erosive 

 activity as to eut through a rising range? I think such a supposition 

 un proved even in other more plausible cases, but in the case of Bur- 

 dekin and Fitzroy I thiük it an impossibility, especially so under 

 the gênerai climatic conditions of that part of Australia, however they 

 may hâve been différent from the présent in the late tertiary times! 



IV. 



AU three excellent studies we hâve been considering in the 

 previous lines agrée that the Australian contiuent extended in the 

 late tertiary time — before the great tectonical events set in further to 

 the east and that its surface was worn down to an almost level pe- 

 neplain rising only imperceptibly to the low watershed. As to that 

 watershed there is a serious divergence between the opinions of Mr. 

 Hedley and Mr. Taylor, which seems to me to be justified, though 

 not to the extent as both authors suppose. 



Before we shall try a reconstruction of the Australian hydro- 

 graphy duriog the peneplain stage — before the commencement of 

 the new cycle — , we must take into considération the probable 

 conditions of the relief and of the climate of that time. 



The country was a peneplain worn down to an almost level 

 country with hère and there some monadnock of hard rocks, partly 

 arrangea in belts more or less parallel to the présent pacifie shore. 

 The extensive areas of the granitic rocks and other older eruptivs 

 certaioly belonged to those monadnocks and Mr. Taylor considers 

 them as forming the former continental divide. The divides were cer- 

 tainly very low, the rivers sluggishly flowing over extensive, almost 

 level plains without much heavy load to transport, of small erosive 

 capacity, tending to divagation, moving only slowly and greatly eva- 

 porating in shallow almost imperceptible beds. Do rivers under such 

 conditions usually flow very far, do they succeed to carry their wa- 

 ters as far as the sea, to break through some hard obstacle — except 

 under most favourable climatic conditions? 



