Plnjalograi^hy of Werribee Area. 267 



by aneroid records taken bv the writer. The idea of plottinj? the 

 grades thus was suggested by a similar piece of work by Nussl>aum 

 (ref. 32j, Nussbaum's diagram lias been carefully re-plotted on a 

 larger scale, and turned in the opposite direction (Fig. 23), to 

 afford easier comparison with the profiles of the Werribee River and 

 tributaries (Plate XllB.). 



The great variety of river types in the Werribee area is due to 

 four outstanding facts. The first of these is the variety of the rock 

 types, which has already been referred to, and the other three 

 include the two important periods of differential uplift, and the 

 great newer volcanic period. Each factor has left its impress on 

 the present river system. 



Before proceeding to discuss these factors, the question arises : 

 Which is the dominant stream, tiie " name-stream," of aiTy river? 

 The matter is important from the physiographic and cartographic 

 standpoints. A physiographer, regarding a map of any river, may 

 conceive it as lopsided, receiving most of its truljutaries from one 

 side only, when perhaps the fact may be that a minor or tributary 

 stream has been given the " name-dominance," by an error of 

 judgment. Similarly cartographers doing small scale maps only 

 include the main stream, according to the name thereof, ar.d if that 

 has been badly selected, the map does not truly represent the facts. 



The writer conceives this to be the case in the Werribee area. It 

 may be shown that from the point of view of depth, age, length and 

 volume the Lerderderg is the most important branch of the Wer- 

 I'ibce System. Economically, however, early settlement of the area 

 tren<led inore along the present day upper Werribee. In 1845-6, 

 when Hoddle, Darke and Urqiihart surveyed the Werribee, etc., as 

 part of the boundary of the country of Bourke, this was therefore 

 the stream surveyed. (See original plans. Lands Department, Mel- 

 bourne.) 



Reference to Figure 23 will show that Nussbauni's "charac- 

 teristic longitudinal sections " place the* main stream always at the 

 lower grade, and, as explained by Hobbs (ref. 32) in the context : 

 ** Lateral streams, from the fact that they are tributaries, likewise 

 descend upon somewhat steeper grades." If now we refer to the 

 actual grades of the Werribee and its tributaries, we find a complex 

 of apparent anomalies — each of wliich may be explained. (Plate 

 XTTB). The point that might be stressed here, however, is that 

 the '' main or trunk stream " — the Upper Werribee— is ever>^vhere 

 at a higher level than the Lerderderg, and may l>e truthfully said 

 to " How into " the latter. It would seem that the comnioiiseiise 



