On the Occurrence of Trachyte in Victoria. 95 



described; they show a tendency to fray out; there are some 

 signs of flow structure. The felspar phenocrysts are sanidine, 

 for the most part idiomorphic : inclusions of apatite and opaque 

 matter are numerous. Small crystals of augite occur with 

 eroded edges ; apatite is present in well formed crystals, and 

 there are traces of mica and epidote. 



Mount Diogenes (Camel's Hump) — the highest point of the 

 range — is a dome-shaped boss, rising to an altitude of 3500 feet 

 above sea-level. The main mass is composed of a rock very 

 similar in outward appearance to the one first described from 

 Turritable Creek. Under the microscope it is seen that the 

 resemblance extends to the internal structure as well. There is 

 the same fluxion arrangement of felspar microliths around well 

 marked sanidine crystals. Zircon and mica are sparingly 

 developed, and there is some chlorite — probably pseudomorph 

 after hornblende. Between the summit of Mount Diogenes and 

 the augite-felspar rock which forms the western extremity of the 

 range, there is a small outcrop of a rather porous rock showing 

 glassy felspar crystals. The base is an irregular mass of grains 

 and ill-formed crystals of felspar ; there is no trace of flow 

 structure. The felspar phenocrysts appear to be sanidine, but 

 they have undergone some alteration ; hornblende, zircon, and 

 needles and crystals of apatite are visible in the slide. The 

 rock is an altered trachyte ; it has some aflSnity to the second 

 specimen from Turritable Creek, and may afibrd a clue to the 

 relation of the trachyte to the other igneous rocks of this part of 

 the range. 



Dry den's Alount. — This is the most northerly point of the 

 " trap " area at which I have found trachyte. Dry den's Mount 

 — better known as the Hanging Rock — rises abruptly from the 

 Woodend plateau. It shows a rude columnar structure in 

 places and its shape suggests the remnant of the pipe or neck of 

 an eroded volcano. It is so much weathered that it was a 

 matter of some difficulty to get fresh specimens. The rock has 

 a light-coloured matrix containing black specks and crystals of 

 glassy felspar. The base is mainly composed of grains and 

 minute crystals of felspar having straight extinction and showing 

 only slight flow structure. As in the slides previously described, 

 the base contains numerous specks of mica and opaque material. 



