1854.] SELWYN — GEOLOGY OF VICTORIA. 301 



everywhere for a short distance from the granite exhibit traces of 

 alteration, being generally more crystalline, harder, and more mica- 

 ceous, but very rarely pass into true mica-schist. 



The whole mass of these sandstones, clay-slates, &c., is traversed 

 by an intense north and south cleavage, as vpell as by a system of 

 large joints, both north and south and east and west ; the former 

 generally dipping at right angles, or in an opposite direction to the 

 cleavage-planes. This system of joints and cleavage renders the true 

 line of stratification very obscure ; they [the strata] appear, however, 

 generally to coincide in strike with the cleavage, but are dipping at a 

 somewhat lower angle ; this can only be detected on a close and very 

 careful examination. 



Coincident with the cleavage, both in strike and dip, and more or 

 less numerous throughout the whole of the palaeozoic strata I have 

 examined, are veins of white and reddish quartz, from a few inches to 

 6 or 7 feet in thickness ; associated with these veins, coating the 

 joints and fissures, we often find much red heematitic iron. In the 

 quartz, occurring in nests and cavities, I have seen — 



1. Gold. 



2. Galena (sulphuret of lead). 



3. Blende (sulphuret of zinc). 



4. Arsenical iron. 



5. White iron-pyrites. 



I have heard of platina having been discovered, but have never seen 

 any. 



I have been unable, as yet, to detect any organic remains in these 

 rocks, and have, therefore, at present no good evidence as to their 

 actual geological age ; judging merely from lithological character, I 

 should, however, consider them equivalents of the Cambrian or 

 Lower Silurian strata of Great Britain, many portions of which, as 

 seen in North "Wales, they precisely resemble. 



The total thickness of these rocks in this district is somewhere 

 about 3.5,000 feet. 



Basalt. — Resting horizontally on Nos. 1 and 2, in isolated patches 

 and large tracts, forming table-lands, flat-topped rocky hills, with 

 steep escarpments, or extensive undulating plains destitute of timber, 

 are large masses of basalt, composed of augite, magnetic iron, and 

 felspar, sometimes hard, heavy, and compact, and often cellular and 

 scoriaceous, especially on the surface, having the appearance of sub- 

 aerial lava. The vesicles are filled or coated with carbonate of lime 

 and oxide of iron, in mammillated crystals. On the weathered 

 surfaces these vesicles are generally empty, the carbonate of lime and 

 the iron being decomposed, and the rock having externally a very red 

 and rusty appearance. 



This basalt is evidently the remnant of vast lava-streams, which 

 appear to have flowed down and filled up the then existing valleys of 

 the country, bringing them nearly to a level with the tops of the 

 lower ranges. Through these lava-streams the present river-courses 

 have been subsequently excavated, always exposing, when cutting 



