266 Charles Fenner : 



-middle tertiary sands, clays, etc. — all largely covered by the later 

 volcanic lava sheet. 



It is deeply cut into by the Parwan, the Werribee, and minor 

 .streams in the east, and by the Moorabool in the west. These 

 streams however have not carved the area into a maze of ridges, 

 as is the case in the Blackwood and Brisbane ranges; a result 

 largely due to the preserving influence of the newer basalt sheets. 

 An isolated patch of extensively dissected Ordovician and granite 

 occurs to the south of Werribee Gorge, where small tributaries of 

 the Werribee and Parwan have done a vast amount of work; this 

 area was never covered by the new^er basalt sheet. The nature of 

 this locality is strikingly seen from the railway line between Bac- 

 'Chus Marsh and Ingliston, since the line travels along somewhat 

 .^bove the general level of the isolated patch of timbered ranges. 



(d) The Gishorne Highlands, — The western portion of this high 

 area is Ordovician, and that rock also probably underlies the whole 

 of the eastern part, the present surface of which is newer volcanic. 

 The Ordovician at the head of Pyrete Creek stands at a distinctly 

 lower level (2-300 feet) than the ranges immediately to the west 

 .(block A), but they are some 7-800 feet higher, on the average, than 

 the volcanic portion of the Gisborne highlands further eastward. 

 The general levels of this ** block " are much less as we go east- 

 ward, grading down to that generally lower portion of the Vic- 

 torian Highlands that marks the '' Melbourne-Echuca line'' 

 referred to by Taylor (ref. 52) as the Kilmore geocol. 



(iii.) Residual Hills. 



(a) The You Yangs. — The name of this impressive range is evi- 

 dently a corruption from the recorded aboriginal name of Wurdi- 

 youan. It is historically the most interesting point in the area, 

 on account of its ascent by Matthew Flinders in 1802. 



Fig. 19 shows the outline of this very familiar landmark, drawn 

 to true scale and projected from the contours of the Military Sur- 

 vey. The mass is wholly granitic, although a small outcrop of the 

 intruded Ordovician slates occurs at one place. The You Yangs 

 must have formed a striking monadnock on the ancient peneplain; 

 there is no doubt that it owes its origin to the highly resistant 

 nature of the rock of which it isi formed. Alluvium and lava flows 

 surround the base, and the apparent height of the mount is 

 exaggerated by the extremely level nature of the surrounding 

 -plains. These hills have already lieen dealt with in complete 



