284 • T. S. Hart: 



or sidewise. As the slopes which stand are soiiietiiues about 10 

 degrees on the surface, it would probably want a steeper slope than 

 this. It might possibly occur at a time of ground movements or 

 warping or elevation, but would ))e exceptional. Wind action 

 would tend rather to fill than to excavate, as the moist bottom of 

 the hollow must be less acted on even if the wind blew up the 

 valley. The existing closed hollows may then be regarded as mostly 

 newly closed. 



General Summary. 



The detail of the drainage system is not to })e regarded as 

 developed on a simple sloping surface. A south-westerly fall is 

 noticeable across the Gardiner's Greek, and, to a less marked 

 degree, tlie Elsternwick Greek area. Slight indications of it are seen 

 even in tlie iJrighton district. A south-Avesterly and sf»utlierly fall 

 is also seen in the Springvale area; and the parish of Mordialloc 

 (i.e., from near Clayton to the main <lrain of the Dandenong 

 (.'rei'k) is under the influence of the southerly fall to the Garruiu 

 Swam]). I)ut the drainage system is largely controlled by tlie 

 dotting Hill-('heltenham axis, i>arallel to which is a subordinate 

 axis through East Camberwell. An easterly tilt from the latter and 

 other late warping movements are probable. iJut primarily the Nottiiig 

 llill-Gheltenliam axis divided the noith-western from the south- 

 eastern streams. The south-westerly tributaries, though important, 

 in many cases seem to be definitely blocked at certain lines, 

 especially that on the south-west sides of Gardiner's Greek and the 

 Springvale \ alley. This feature, combined with tlie extreme re- 

 gularity of the Brighton system, and the structures of the rocks 

 so fai' as seen, favours the idea that the streams are guided or 

 St lengthened on theii' south-east or north-west courses by lines of 

 wt-akness or by structural featmes. and that there may even have 

 been original reversals of .slojte against the south-west fall in some 

 cases. 



.\11 the valleys in their earliei- stages weie in the weak and 

 ab.soij)tive tertiary sandy beds. On reaching impermeable beds 

 siu^h a valley would leceive additions from springs, and weak 

 jdaces would be produced on the lines of springs which might 

 It-suit in a great power of widening the valley or cutting a tributary 

 valley. 



(Tosed hollows are of fiequcnt occurrence, and are easily pro- 

 duce<l owing to the extreme weakness of the upper juirts of the 

 Rtreams. Small local causes may have possibly produced some, but; 



