390 PKOCEEDINGS OF SECTION C. 



necessarily wanting in detail. My own traverses of the area have 

 been chiefly along the main roads, and I am not, therefore, able to 

 do more than point out a few inaccuracies in the geological map. 



The granites, porphyries, crystalline schists, &c., which form the 

 chief rock masses, vary exceedingly in appearance as well as in 

 structure. Towards the southern and western boundaries of the 

 county especially the rocks present some peculiarity in almost every 

 fresh quarry opened. 



The three principal groups of eruptive rocks present in the area 

 will be taken in their order of geological sequence, beginning with 

 the most ancient. A fourth group, viz., the Newer Basalt, which 

 overspreads a great part of Normanby and has invaded the south- 

 eastern limits of Dundas, is so well-known that I will not occupy 

 the time of the section by describing it. 



PLUTONIC. See Plate XIY. 



Granite. — In the geological map of Victoria a central boss of 

 granite is shown in the county of Dundas. In reality, it extends 

 farther north than the map indicates, as for a few miles to the north 

 of the Glenelg, in the neighborhood of Harrow, the hills are com- 

 posed of this rock ; in fact for some distance the river has cut its 

 way through granite. In places to the south also, though its 

 exposures on the surface are infrequent, one is often surprised to 

 find an outcrop of granite here and there. Thus at Carapook a 

 granite outcrop is surrounded by volcanic rocks, and at Coleraine 

 it appears suddenly amongst similar strata. At Wando Vale, near 

 Casterton, a granite hill is surrounded by Mesozoic and volcanic 

 rocks. Again, to the west of the central boss, there are granite 

 outcrops of considerable extent at Tarrayoukyan and Koolomert. 

 On the eastern side the granite extends close to Balmoral, the south 

 road from this town to Harrow being mainly through granite 

 country. On the west of the Glenelg, on the Dergholm to Apsley- 

 road, a smaller boss of granite is marked on the map. This also 

 should be mixch extended, as it reaches to the river on the east, 

 and beyond Dergholm on the south. Owing to the quantity of 

 drift sand in this region, it is difficult to define the exact limits of 

 the granite. Between the Serra and Victoria Kanges a granite 

 area is also mapped, but the rock is of a different character to that 

 in the other chief localities. 



The rocks of the central area are for wide distances covered by 

 Tertiary and recent drifts, so that a detailed geological survey would 

 indicate in some of the localities only strings and apparently 

 isolated patches of granite instead of the imbroken outline of the 

 published map. In places it disappears altogether, and often 

 abruptly. Thus at Wando Dale there is granite on the east of the 

 road, but on the west the River Wando has cut a deep channel 

 through the volcanic surface rocks, and then through the under- 



