Fhi/siographi/ of Yarra, etc. 501 



its way baekwards in a south-easterly direction. This is the 

 jiresent lower (xardiner's Creek. At the same time the Main 

 Creek ran south-westerly across Murrumbeena, and thence 

 down to the sea in a southerly or south-westerly direction, 

 generally speaking. It was joined by the creek farther west, 

 and, possibly, by a tributary running south-easterly, this 

 tributary being now part of the present Gardiner's Creek. 



The Yarra cut its channel quickly, and so gave a rapid fall 

 for the short Gardiner's Creek. Main Creek had only a small 

 drainage area ; its erosion therefore would be much slower than 

 the Yarra, and the fall would not be so great. Gardiner's 

 Creek would tend therefore to rapidly cut backward, and 

 possibly gradually annex the western stream, and ultimately 

 Main Creek. The old stream south of Murrumbeena woula 

 thus be beheaded, and its upper waters diverted into the 

 Yarra instead of into Port Phillip Bay direct. The lower 

 valley of the old Main Creek would then be too wide for its 

 drainage, and smaller valleys within the old valley would 

 originate, some running towards the sea and others to the 

 present Gardiner's Creek. 



That some such series of changes has taken place is pos- 

 sible, but not certain. 



The direction of the present Main Creek, and the creek to 

 the west, the somewhat depressed country between Oakleigh 

 and Malvern, and the direction of Gardiner's Creek across the 

 slope of the country are explained by the suggestion made. 



On the other hand, the denudation south of Gardiner's 

 Creek has been so slight on account of the small drainage area 

 and the low elevation of the ground that it is difficult to gather 

 strong evidence of the changes. Another difficulty is Scotch- 

 man's Creek. Tliis runs north-westerly into Main Creek, near 

 the junction of the latter with Gardiner's Creek. It is possible 

 that this was originally a short tributary of the old Main 

 Creek. After capture of the heads of the latter by Gardiner's 

 Creek, it offered a favourable channel for the backward erosion 

 of the latter, and thus perhaps it has grown. 



Another difficulty is the course of the Elsternwick Creek. 

 This runs approximately parallel to Gardiner's Creek, and re- 

 quires an explanation if the changes suggested have taken 



