PhysiograpJiy of Yarra, etc. 471 



East of this line is the basin of the Middle Yarra, Kooweerup 

 Swamp and AVesteni Port, which were probably once part of 

 a connected basin. 



In the same work (pp. 106-107) Prof. Gregory points out 

 tliat the Yarra does not cross from its middle basin to its 

 lower basin by what appears to be the natural course — viz., 

 through the gap at Mooroolbark used by the railway, but after 

 meandering through the Yarra Flats the river suddenly turns 

 off into the hilly countiy known as the Christmas Hills. It 

 flows in a deep gorge through them till it reaches the plains 

 again near its junction with the Plenty River. Its course he 

 maintains is therefore clearly antecedent to the present topo- 

 graphy of the country : but its narrow gorge and rocky cata- 

 ract broken course show that it has here the characters of a 

 young as well as an antecedent river, and is, in fact, a revived 

 river. 



Tlie possible peneplain of which the tops of Mt. Macedon 

 and the Dandenong Ranges are the remnants, as suggested by 

 Prof. Skeats (3, p. 188), will not be discussed in this paper. 



Genepai Descpiption. 



Tlie principal physical features of the areas in question are 

 fairly well known, so that a brief description will be sufficient 

 for the purposes of this paper. 



Treating the Yarra first, this river rises near Mt. Baw Baw, 

 and thence passes westward, developing into a fairly open, 

 matured valley, with well-developed tributaries, until it reaches 

 Warburton. Here, as noted by Mr. F. G. A. Barnard (4, p. 

 245), it is confined to a deep and somewhat narrow gorge, after 

 passing which its valley gi-adually widens until it turns to the 

 north near Killara, and meanders through broad alluvial flats 

 as far us Healesville, where it savings away again to the west- 

 ward through similar flats as far as Yarra Glen. It then turns 

 to the south-west, still bordered by flats, but now principally 

 on the left bank only. Tlie right bank rises steeply to a con- 

 siderable height above the river, and these features are main- 

 tained, with the exception noticed below, until Brushy Creek 

 (a southern tributary) is met. 



