Physiography of Yarra, etc. 503 



hard rocks of which it is composed. Tlie surrounding rocks 

 are soft silurian sediments. The geology of this hill presents 

 some interesting features, and is being worked out by Mr. F. 

 Chapman and myself. 



" Pineniont," Croydon Hill and Burt's Hill. 



'■ Pinemont " and Burt's Hill are on the line of the Mitcham 

 Axis. This is rather a striking coincidence, but whether 

 actually climbed, or viewed from a distance, as from near 

 Kangaroo Ground, they appear to be undoubted monadnocks. 

 Their occurrence on the Mitcham Axis suggests the possibility 

 that this axis was perhaps in existence at the time of ujDlift of 

 the Nillumbik Peneplain, due to being the old water-parting 

 between the old Yarra and Dandenong Creek Basins. The 

 antecedent character of these streams would permit of this con- 

 clusion being drawn, and as the water-parting is generally 

 least denuded, monadnocks would naturally occur there. 



In addition, even when reduced to a peneplain, gentle slopes 

 on either side of the water-parting would exist, and might be 

 preserved on uplift. If this be the true history of the case, 

 then the sviggested tilting to the north and south of the 

 Mitcham Axis might not hold good. To some extent therefore 

 this question must be left open. 



Mr. Thiele (7, p. 103) has referred to "Pinemont" as a con- 

 spicuous conical hill rising to about 600 feet above sea level, 

 and marking the position of the old water parting. This hill 

 is a conspicuous landmark from many parts of the country. 

 PerhajDS the best view of it is from the Surrey Hills Reservoir, 

 from which its residual character is clearly seen. It rises 

 about 100 feet above the level of the peneplain at its base. It 

 is difficult to account for the projection of " Pinemont '' from 

 the nature of its component rocks. These so far as visible are 

 not appreciably different in their hardness from those of the 

 surrounding country. 



Croydon Hill occurs a little to the south of Burt's Hill. 

 They both rise about 100 feet above the level of the Nillumbik 

 Peneplain at their bases. The peneplain is here about 560 feet 

 above sea-level. Thev are rather elongated conical hills. Their 



