president's address. 23 



shed is passed at the hills above Lake George. Then descend- 

 ing along the Murrumbidgee the broad floor of the valley is 

 traversed on which the Murray is twice crossed. Not niilil 

 after six or seven hundred miles of travel is the opposite 

 watershed gained at Mt. Lofty above Adelaide. 



Perhaps the most interesting tale yet told of the physio- 

 graphy of New South Wales is the vivid story by Dr. Wool- 

 nough and Mr. T. G. Taylor* of how the Upper Shoalhaven 

 River formerly flowed into the Wollondilly, thence into the 

 Nepean and so into the Hawkesbury. Thus it reached the 

 sea after following a course of about a hundred and sixty 

 miles, roughly parallel to the coast and distant from it about 

 forty miles. A crisis in its history occurred. Not only did a 

 pirate stream, the Lower Shoalhaven, behead the former 

 Wollondilly, but a further capture of Wollondilly water is 

 imminent in the near future. In the past the Moruya and 

 the Tuross Rivers have each taken a length from the old 

 river. No marginal stream could have the power to excavate 

 and capture possessed by a radial hence the former must 

 always fall a victim to the latter. These threats and cap- 

 tures are attempts and successes to proceed from marginal 

 to radial drainage, to progress from the abnormal to the 

 normal. 



In the accompanying sketch (Fig. -t) the long valley of the 

 Shoalhawke (to coin a convenient name by connecting tlif old 

 source with the old mouth) is drawn as desci'ibed in the 

 memoir cited, but extended southward as recently suggested 

 to me by Dr. Woolnough. It is clear that this river could 

 not have pursued this eccentric course during the last pene- 

 plain period. For under peneplain conditions gravity would 

 force a stream to base level by the shortest way. Through 

 almost level country a river must take full advantage of 

 what little slope it has or it would stagnate. A river flowing, 

 for instance, into the Gulf of Carpentaria could not sfford 

 to waste its fall by setting a course parallel to the coast. 



* These Proceedings, xxxi., 1906, pp. 546-554. 



