340 il/or/-;.s Morris: 



The high percentage of silica (OS per ct-nt.), ainl of alkalis (().*.)8 

 per cent.), constitute this i-ock a tdscaiiite. aocnnling to HatrlTs 

 classitication. 



I'he Giolof/lcal Map. — This series is coloured Silurian on Sehvvn's 

 sketch map, and on the geological map of Victoria, having been 

 regarded as altered sediments by Murray (7) and Stirling (8). The 

 latter coloured this and the succeeding series (b) Silurian in his 

 map of Lilydale, and shows in his section a hypothetical trappean 

 mass under the township to account foi- their alteration. 



h. The Upper Tat'caiiitf Sfr/'eg. 



The visible distribution of this series lesenibles a sliepherd's 

 crook, the crook bending east at Lilydale. and enclosing the succeed- 

 ing series of the system. From Lilydale, where it forms part of the 

 surface rock, it runs south for seven miles, forming a narrow stiip 

 between the Silurians and the Lower Daeite series (c). 



Petrolor/ical Cliaracfer. — The whole series is characteristically 

 homogeneous. The only variations are due to the alteration of 

 effusive and explosive phases. The explosive types, varying from 

 lapilli to agglomerate, are generally preserved in the form of 

 hills, and some of these are probably close to, if not on the sites 

 of, the volcanic vents. They are well developed opposite the Sal- 

 vation Army farm, near Bayswater, and near Montrose. In the 

 extreme northern part of its distribution, these fragmental types 

 occur almost continuously over a large area, and they appear to 

 become increasingly coarse towards a pair of high conical hills as 

 centre, where the agglomerate contains fragments as big as a man's 

 head. I, therefore, regard these two hills as denuded necks of 

 Devonian toscanite volcanoes, and have marked them as such on the 

 map. 



The following is a description of the normal effusive rock when 

 fresh : — 



Macroscopic. — A blue-black, non-vesicular, compact, exceedingly 

 fine-grained, brittle rock, intricately traversed by joint planes, 

 and showing rather sparingly lustrous phenocrysts of felspar. 



Microscopic. — Phenocrysts consist of plagioclase, .some of which is 

 determined to be oligoclase and andesine, idiomorplic, but some- 

 times corroded; glassy sanidine subordinate; biotite occasionally in 

 small flakes ; apatite, zircon, rutile, and rectangular crystals of 

 iron oxide. The ground mass is microcrystalline. It contains a 



