feY R, H. CAMBAGE. 681 



roomba, the Gudgenby River, in places alternating with slate, on 

 the range separating the Upper Gudgenby waters from those of 

 the Cotter, and on the summit of Birnberi Peak or Mountain. 



No evidence of glaciation was noticed on Birnberi, but it was 

 not specially searched for. The absence of a suitable gathering 

 ground, however, would alone probably be sufficient to account 

 for its absence. 



The valley of the Cotter, in the vicinity of Bimberi, and the 

 side of Bimberi, up to at least the 5,000 feet level, are of slate 

 formation, probably Upper Silurian, and this accounts for the 

 great denudation which has been effected by the Cotter River 

 operating on the softer rocks, for it was noticed that the highest 

 hills in the locality are granite. 



The summit of Tidbinbilla was found to consist of quartzite 

 and slate, the former supplying the resisting qualities. 



The central-eastern portion of the Territory consists largely 

 of quartz-porphyries, and produces an open forest vegetation. 



Mount Coree is composed of igneous rocks, a specimen from 

 the summit being considered by Mr. G. W. Card, A.R.S.M., 

 without critical examination, as of the rhyolite or rhyolite-tuft' 

 class. This rock splinters in a remarkable manner, and under 

 the bluff at the south-west end, narrow strips may be seen up to 

 10 feet long. 



A few miles south of Coree, and also where the main road 

 crosses Coree Creek, the forn)ation is slate. 



A good example of the effect of geological formations on the 

 vegetation may be seen from the City site. To the north east 

 are the slopes of Mount Ainslie (2,762 feet), composed largely of 

 volcanic tuffs, and clothed with open forest, while to the north- 

 west is the coarse sandstone-hill known as Black Mountain 

 (2,658 feet). The name of the latter was suggested by the dark 

 appearance of the more dense foliage of this hill as compared 

 with that on the surrounding elevations, but this mass of vege- 

 tation is a direct response to the more siliceous sandstones of 

 wliich the eminence is composed. 



