1857.] 



SMYTH EXTINCT VOLCANOS OF VICTORIA. 



229 



is commonly found on the plains ; but at the base I found some 

 labourers quarrying a hard, dense, bluish-grey basalt, with included 

 crystals of quartz. The basalt through which the Saltwater River 

 has cut a channel has undoubtedly proceeded from Mount Aitkin 

 and the neighbouring peaks, and it now fills the old basin formed 

 in the palaeozoic rocks ; but it does not appear to have altered the 

 physical configuration of the country very remarkably. Indeed, 

 when we look at the Keilor Plains, and examine the thickness of 

 the basalt in many places, the fact is apparent that the surface of 

 the ancient sedimentary strata must have been moderately even and 

 uniform when it was covered by the igneous rock. 



At Keilor a fine section of the basalt may be seen. Its relation 

 to the palaeozoic rocks is shown in the section, fig. 2. 



Fig. 2. — Section at Keilor. 



1 . i . ' i ! i ! • . . ' . i , i 



a. Basalt, b. Hard quartzose conglomerate, c. Contorted Silurian rocks. 



The extinct volcano Mount Aitkin has broken through the Silu- 

 rian rocks, and these may be seen in many places in its vicinity 

 rising above the sheets of lava. 



3. Mount Boninyong is immediately adjacent to the Ballaarat 

 gold-fields. It has a distinct crater. Masses of very porous lava 

 are found in the neighbourhood, so light that it is easy to lift frag- 

 ments several feet square. The lava covers the older auriferous drift; 

 and the newer drift, also containing gold, rests on the top. 



4. Lame-bar amul* : , or Mount Franklyn, is one of a group of ex- 

 tinct volcanos which are found both to the north, south-east, and 

 west. On the steep side of the hill, the rock is in huge irregular 

 blocks. Here, as in other parts of the district, the lava has fol- 

 lowed the course of the channels which were already formed at the 

 period of eruption, and the streams have extended to a great 

 distance, much of the auriferous drift on the Loddon being covered 

 up by the igneous rock. 



5. The MS. plan given of Mount Rouse explains its general 

 character. In the vicinity of the mount there are numerous springs 

 and swamps, and caves of considerable extent have been found. 



* " Home of the Emu." Manuscript plans of Mount Franklyn, Mount Rouse, 

 Mount Leura, and of Tower Hill Lake, from recent surveys, accompanied this 

 memoir, and are deposited in the Society's Library. — Ed. 



