IGNEOUS ROCKS OF SOUTH-WESTERN VICTORIA. 393 



uncertain." The first hypothesis is probably the correct one. 

 Close to the quartz prophyries on the Balmoral-road there are 

 altered sandstones, but they are quite unlike the crystalline schists. 

 That the latter have no essential connection with either the 

 granites or porphyries is evidenced by their occurrence in localities 

 where the plutonic rocks are unknown. 



Qnartz-porphi/ry. — Large porphyritic crystals of orthoclase and 

 quartz occur in this rock, scattered through a very fine-grained 

 matrix. T'here is also a quantity of fine dusty matter, which 

 remains opaque in thin slides. In color the rock varies from 

 almost white to brown. Its sp. gr. is 2*58, and the percentage 

 of silica is 74-7. Usually the porphyry is found in a fresh con- 

 dition, but near Cavendish the surface rocks are much de- 

 composed. Towards the northern boundary of the outcrop a 

 rock of a light greenish color, quarried for road metal, is, 

 I think, also a highly decomposed portion of the general mass. 

 In this the porphyritic crystals of felspar have mostly become 

 kaolinised, but in hand specimens a few specks of unaltered 

 quartz are still visible. 



The town of Cavendish is built on a blackish-looking rock, of 

 so close-grained a texture that the thinnest possible slides remain 

 to the last quite opaque. It is almost, but not quite, destitute of 

 porphyritic structure. By close observation small crystals of both 

 felspar and quartz may be detected. Though so diiferent in 

 appearance from the porphyries of the neighborhood, it should 

 doubtless be classed as a compact variety of them. 



About four miles south-east of Cavendish, on the Dunkeld- 

 road, a small rounded hill, dignified by the name of Mount 

 Cavendish, and marked as basaltic on the geological map, is 

 composed of unaltered typical quartz-porphyry. I have not 

 visited the hills on the east of the Balmoral-road, just north of 

 Cavendish, but from their appearance, as seen at a distance, I have 

 little doubt of their being composed of the same rock. 



On the eastern flank of the Dundas Range the porphyries show 

 in a small creek, and present a laminated appearance as if they 

 had been poured forth in sheets. This creek is on land belonging 

 to a selector, who, though he aided me most willingly in my 

 search for outcrops of the rock, has a very poor opinion of it, as 

 he concludes from bitter experience that its occurrence indicates 

 a most unproductive soil. 



The boundaries assigned to the Dundas quartz-porphyries on 

 the geological survey map must be considerably extended. 

 Commencing on the north at a point about ten miles south-east of 

 Balmoral, they continue along the syncline of the Victoria and 

 Dundas Ranges do\NTi to Cavendish, and for some distance to the 

 south of that township, when they pass under basalt. 



Turning to the south and south-west, the outcrop crosses the 

 Wannon at Nigretta Falls, and continues through Bochara, and on 



