296 Charles Feiiner: 



about 200 feet deep, while on the east the Parwan tributaries run 

 steeply down to a depth of over 600 feet. The area between, less 

 than three miles wide, is almost level, and both streams have small 

 tributaries heading back to within a mile of each other. This 

 level tract is a remnant of the once more extensive newer basalt 

 sheet, and the part shaded horizontally stands above the 1400 feet 

 contour line. A shallow south-flowing valley has chosen a cen- 

 tral course, midway between the two competi^ig streams and in the 

 part left unshaded in the plaD (between 1350 feet and 1400 feet) it 

 forms a swamp in winter. (Fig. 37). 



There is no doubt that we have here a case of (geologically) immi- 

 nent capture. The southern bounding fault of the Ballan sunk- 

 land passes E.-W. through the central part of the swamp (beneath 

 the basalt sheet). South of that line the bedrock is hard Ordo- 

 vician, while to the north the basalt is underlain by the soft ter- 

 tiaries. The captuie should therefore take place to the north of 

 the swamp, probably about the point where the two hachured tribu- 

 taries most closely approach each other. The Parwan headwaters 

 here have a much, steeper grade than the Eastern Moorabool tribu- 

 taries; both sets of streams are dry for the greater part of the 

 year. Again, speaking geologically, we may look forward to the 

 capture of the Eastern Moorabool by the Parwan even earlier than 

 is suggested by Mr. Hart (ref. 22, p. 269). 



The next great expanse of plain is that of the Lower Werribee 

 (" Iramoo.") This aboriginal name was probably originally 

 applied only to the more northern portions of the plains. These 

 plains are wide and bleak, and are almost wholly volcanic, in 

 places overlain by later alluvium. Here and there are small 

 patches of timber, mainly box-trees, but these are most likely on 

 places where an area of alluvium provides the necessary depth of 

 soil. There is a general slope to the sea (see Fig. 12), and swamps 

 are fairly common, especially close to the coast-line. The drainage 

 is, of course, young, and is effected by the Werribee with the Skele- 

 ton Water Holes and Kororoit Creek to the north, and Little River, 

 etc. to the south. A chain of swamps crosses the Bacchus Marsh- 

 Geelong road, between Bald Hill and Parwan, and testifies to the 

 backward stage of the drainage system in this portion of the 

 plains. 



The idea is put forward by Kitson (ref. 37) that the sea once 

 extended over these plains, and that much of the lava was sub- 

 marine. He bases this on the thickness and extent of pebbly drift, 

 such as may be seen in exposures at Exford, etc. Examination by 



