262 N. R. .fanner: 



of a different, nature, being <letermine(l by a mass of liurnfels with 

 softer unindurated sediments upstream and downstream from the 

 hornfels. 



The rocks are usually covered by dense undergrijwtli, especially 

 so in the valleys, which ai-e often impassal)le. The soil covering- 

 is very deep in places, and hill-slip material is often abundant, 

 rendering geological mapping very difficult. Coarse bouldery 

 gravels are present in the upper reaches of all the streams, and in 

 inaccessible country of this nature they afford valuable infor- 

 mation as to the character of the rocks within the watershed of the 

 streams. 



The dacitic rocks from this area possess many features in common 

 with the dacites described from Mount Macedon by Professor 

 Gregory,! and by Professor Skeats and Dr. Sunmiers.2 Rhyolites 

 and pyroclastic rocks of (?) Devonian age are apparently absent at 

 Macedon, although they are jjresent at various points in the Heales- 

 ville district. It was with the primary purpose of studying these 

 less well-known rocks in the latter area, that the present research 

 was undertaken by the writer. 



2.— Previous Literature. 



In 1854 Sir A. R. C. Selwyn^ pi-epared a geological map of por- 

 tion of the country to the east and south-east of Melbourne. The 

 Healesville igneous rocks are roughly delineated and referred to as 

 trap. In the accompanying report Selwyn stated that hornblendlc 

 granite passed into porphyry near Mount Monda. 



In 1894 J. C. Newbery* described rocks from the Blacks' Spur 

 and Fernshaw as mica porphyrite and felspar porphyrite respec- 

 tively. 



In 1901 E. G. Hogg-'* bi-iefly described the microscopical charac- 

 teristics of a granitic rock from the Watts' river aqueduct. He 

 determined it to be a fine-grained granitite composed of felspar, 

 with plagioclase in excess of orthoclase, quartz, biotite, apotite. 

 chlorite, calcite and muscovite. 



In 1902 Professor Gregory, 6 in an important contribution deal- 

 ing with the Macedon igneous rocks, briefly described the allied 



1 Vide infra, p. 3. 



2 "The Geology and Petrology of the Macedon District." Bull. Vict. Oeol. Siirv., No. 24, 1912. 



3 " The Geology, Paleontology and Mineralogy of the Country situated between Melbourne, 

 Western Port Bay, Cape Schaiick, etc." Kep. Geol. Siu'v. \'ict., Nov. 1S54. 



4 " Descriptive Catalogue of the specimens of Rocks of \'ictoria, in the Industrial niid Techno- 

 logical Museum, Melbourne," 1894. 



5 " Petrology of Victorian Granites." Proc. Roy. Soc. Victoria, vol. xiii. (n.s.), 1001. 



6 " The Geology of Mount Macedon." Proc. Roy. Soc. Victoria, vol. .\iv. (n.s), Pt. ii., 1002. 



