128 THE VICTORIAN NATURALIST. 



canite sand. Following a tributary of the Britannia Creek the 

 principal rock met with, at a height of about 900 feet above sea 

 level, was a huge mass of Granodiorite or Granitite, the typical 

 granite of the older surveyors of the colony. 



Notes on the Rock Specimens ■.^- 



Granodiorite. — In a tributary of Britannia Creek. 



This rock is characterized by the felspars being almost essen- 

 tially of the ])lagioclase types. Quartz fairly common, allotrio- 

 morphic, rarely idiomorphic. Plagioclase felspars, frequently 

 zoned. Much biotite. Apatite occurs sparingly. Tourmaline as 

 inclusions in quartz. The felspars are in many cases undergoing 

 metasomatic or internal chemical changes. 



Granulitic Diorite. — Don River Valley. 



An augite diorite, having a granulitic base or ground mass of 

 small rounded plagioclases. Porphyritic crystals of plagioclase 

 occur scattered throughout, sometimes determinable as oligoclase. 

 Also much green augite, nearly always enwrapped by a coat of 

 small platy brown hornblendes derived by dynamical metamor- 

 phism from the augites which still form a nucleus. A fine 

 rhombic pyroxene, presumably hypersthene, occurred in one 

 example. The rock has evidently suffered much deformation, 

 and is quite gneissose in hand specimens. 



Dacite. — Don River, near junction with Silurian. 



This rock somewhat resembles the Willimigongong type 

 described by Professor Gregory from Mt. Macedon, but the 

 groundmass is micro-crystalline, with evidence of fluxion structure. 

 It is crowded with phenocrysts of quartz, felspar, and mica. The 

 felspars are plagioclastic and idiomorphic (with crystalline 

 boundaries) ; they are frequently corroded, and many contain 

 inclusions. The quartz, although in idiomorphic crystals, is as a 

 rule rounded and corroded by the magma, and the crystals are 

 often fractured. Biotite common. Apatite rare. 



Although there are several quarries and cuttings in the district, 

 the locality is unfavourable for fossils, the only specimen seen 

 being the markings of a fucoid in some grey argillaceous Silurian 

 rock. — F. Chapman. 



At the Summer School for Teachers, at present being con- 

 ducted by the Education Department, nature study is taking a 

 prominent position. Messrs. J. A. Leach and H. T. Tisdall, 

 members of the Field Naturalists' Club, are lecturing on 

 zoological and botanical subjects. 



The first award of the Baron von Mueller medal for original 

 researches in Natural Science, referring especially to Australasia, 

 has been made by the Australasian Association for the Advance- 

 ment of Science, now sitting at Dunedin, to Mr. A. W. Howitt, 

 F.G.S., of this State, for distinguished work in ethnology, geology, 

 and botany, extending over forty years. 



