With regard to the altitude at which this peneplain was 

 formed, we know that wherever one now finds a plain near 

 the seaboard in eastern Australia elevated even a few 

 hundred feet above sea level, one may also find ravines 

 traversing that low plateau. It is a safe conclusion then 

 that the peneplain of eastern Australia which existed 

 immediately prior to the Kosciusko Period was formed at 

 a height not much above sea level. 



As to the age of the present mountain systems of eastern 

 Australia one can see at a glance that they are only as old 

 as the gorges which dissect them. From paheontological 

 and mechanical considerations these are almost certainly 

 not older than the close of the Tertiary or the commence- 

 ment of the Pleistocene Period. 



By the faulting and Hexing action of the Kosciusko 

 Period certain streams were forced to take up meridional 

 courses. The movement was slow because strong streams 

 were able to hold their own against the uplift. In the 

 Human Period ;i general submergence of eastern Australian 

 coasts took place and by this movement a series of mag- 

 nificent harbours came into being. 



(B) The evidence of the Leads of the " Newer Volcanics." 

 Under the previous sub-heading a general statement of the 

 topography of the plateaus was supplied. Nevertheless 

 there are many important details which modify this general 

 description. Thus it has been shown that the main outlines 

 of the upland topography have been formed out of Pre- 

 Tertiary rock structures. The old plateau surface, how- 

 ever, is capped in places with wide sheets of basaltic lava, 

 which in turn overlie "deep leads" (that is buried river 

 deposits). These deep leads occupy definite channels, and 

 they belong to two distinct periods of deposition. 



"Deep leads " of still more recent age occur under thick, 

 masses of alluvium formed in the embaymentsof the Great 



