BY E. C. ANDREWS. 511 



The undercuttings of banks and spurs would be incomprehensible 

 except as products of weathering and landslips. The shriekings 

 and crashings of the boulders under the influence of a flood along 

 a torrent track would be altogether denied, since it would be 

 carefully noted that even the Amazon — the greatest of river 

 streams, as the Arctic and Antarctic glaciers are amongst ice- 

 streams — under the normal conditions perceptible only to them, 

 fails to rouse to action its load of flood debris, but loiters and 

 babbles only amongst the pebbles and boulders. 



And the one thing needful to clear away the doubt would be 

 an apprehension of the fact that a drought-stream cannot reduce a 

 grade along which the mightiest floods have acted so as to approxi- 

 mate their channel bases to, if not to actually reach, that transi- 

 tional grade when they themselves even have parted with most of 

 their efficiency as vertical corraders. 



(4) Streams of Eastern New South Wales. 



These are weak streams, and nowhere possessed of a greater 

 length than 330 miles. 



The Hawkesbury (Wollondilly). — The Upper Hawkesbury or 

 Wollondilly near Wombeyan flows through the dense granites in 

 a profound gorge 2,100 feet in depth (PL xxxix.). It is evident at 

 a glance that it is still actively downcutting, having, as yet, found 

 no opportunity for lateral cutting in the acid igneous series 

 through which it flows. Yet here, more than 200 miles from its 

 mouth, and not far removed from its source, it is 625 feet only 

 above main base-level; while the enormous upland valley, 15 to 20 

 miles in width, through which it has cut its way is some 2.700 

 feet above the same level. The canon, the far stretching upland 

 valley, and the still higher and older enveloping plateau, are 

 alike carved, in places, out of fairly homogeneous Palaeozoic 

 granites 



The Wollondilly has then not attained to its transitional grade. 



The Macleay (New England). — The headwaters of this stream 

 wind sluggishly for distances of from 20 to 50 miles in the 

 matured valleys (3,200 feet above sea-level) of the Upland Level. 



