260 //. 6'. Savivier.s: 



overlain by the Maiistield sandstones. Tliere is some little (lou])t as 

 to the age of these sandstones, as McCoy (11) described tliem as 

 equivalent to the Old Red sandstone, hut latei- Woodward {2-t) has 

 placed them in the Lower Cai-boniferous. In any case, however, the 

 age of these rocks in the north-east of Victoria is confined to fairly 

 narrow limits. They are post-Silurian and pre-Lower Carbon- 

 iferous, i.e., they aie almost certainly Devonian. Enormous earth 

 movements marked tlie opening of the Devonian in Victoria, and 

 there is no evidence of intense earth movement in Middle and Upper 

 Devonian, so that the inference is that the intrusion of these igneous 

 rocks accompanied these Lower Devonian eartli movements, and 

 consequently are of Lower Devonian age. 



The closely-marked similarity between the mineralogical and 

 micro-structural features of the dacites and the quartz porphyrites 

 lead one to the conclusion that they belong to the one great period 

 of igneous activity, so that the dacites and grano-diorites of 

 Macedon, Dandenong and Healesville, in the absence of other 

 evidence, may be classed as Lower Devonian. 



Dr. Howitt (7) has shown that the Snowy River porphyries are 

 Lower Devonian in age, so that there is a strong probability that 

 the dacites and Snowy River Porphyries are genetically related. 

 Unfortunately the Snowy _River Porphyries cannot be included in 

 this discussion, as no analyses of these rocks have been made. 



In Central Victoria are numerous occurrences of granite rocks, 

 and there range from granodiorite through adamellite to normal 

 granite. 



Mr. Stillwell (20) has described the granitic rock of Broadmead<nvs 

 as adamellite, and gives an analysis by Mr. H. C. Richards of a 

 specimen from Gellibrand Hill. Professor Skeats (16) has described 

 the rock from Mount Eliza, in the Mornington Peninsula, as a 

 grano-diorite, and gives an analysis of the rock estimated by means 

 of Rosival's method. The large mass of granitic rocks extending in 

 a rude semi-circle to the north of Castlemaine and Maldon contains 

 various types, but that from the Harcourt tjuarries is on the border 

 line between the adamellites and granodiorites. An analysis of this 

 rock Avas made some few years ago by Mr. C Ampt, and is given 

 later. 



North-west of Bacchus Marsh, near Ingliston, is an intrusion of 

 adamellite (provisional name). This has been analysed by Mr. A. 

 (i. Hall at the Mines Department Laboratory, and the analysis will 

 be given later. 



