1854.] SELWYN— GEOLOGY OF VICTORIA. 299 



March 8, 1854. 



Neville Story Maskelyne, M.A., Dep. Professor of Mineralogy, 

 University of Oxford ; B. Waterhouse Hawkins, Esq., S. P. Wood- 

 ward, Esq., and Charles Wentworth Dilke, Esq., were elected 

 Fellows. 



The following communications were read : — 



1. On the Geology ftwc? Mineralogy oy Mount Alexander, 

 and the adjacent Country, lying between the Rivers Loddon 

 and Campaspe. By Alfred Richard Cecil Selwyn, Esq., 

 Director of the Geological Survey of Victoria. 



[Communicated by Prof. A. C. Ramsay, F.G.S.] 



The whole of the above district is occupied by four different 

 geological formations — 



1. Granite. 



2. Metamorphosed palaeozoic strata. 



3. Basalt. 



4. Auriferous drift. 



The extent of country occupied by the first three of the above for- 

 mations may be seen on referring to the accompanying map * ; [by 

 which it is shown that Mount Alexander forms part of a granitic 

 range, extending from the River Coliban, on the east, to the Loddon 

 on the west, with a breadth varying from four to twelve miles, and 

 describing an irregular semicircle, with its convexity to the north. 

 The granite is bounded on all sides by metamorphic rocks ; and at 

 its eastern extremity it is overlaid by patches of basaltic lava, amongst 

 which the Coliban runs. The basalt occurs also to the east of the 

 Coliban in still greater extent, overlying the metamorphic rocks along 

 the course of the Campaspe River. At the western limit of the 

 granite also, similar basalt forms the lava-plains on the Loddon.] 

 The fourth is more or less universally distributed over the area occu- 

 pied by the second. 



Granite. — The granite everywhere forms an open forest country, 

 consisting of high rocky ranges and undulating grassy hills ; enormous 

 blocks, standing out in bold relief, lie scattered on the summits and 

 flanks of the hills, often affording the most picturesque scenery. 

 These blocks are always in situ, and are the result of the decomposi- 

 tion of the softer portions of the rock. The rock itself is, for the 

 most part, a coarse-grained ternary granite (quartz, felspar, and 

 black and sometimes yellow mica), often very soft, friable, and easily 

 decomposed. In some few places the granite appears to pass into 

 Pegmatite, a compound of quartz and felspar. It generally possesses 

 a large spheroidal or concretionary structure, composed of concentric 



* [This map has been piil)lished in the First Report of the Geological Surveyor 

 of Victoria.] 



