Geological History in Palaeozoic Times. 
65 
With the appearance of land surfaces commenced littoral and 
terrestrial denudation ; the uptilted edges of the rock-bands were 
abraded and worn down ; their entire removal in places caused the 
first appearances of granite at the surface ; and the formation of 
new rocks began to take place in the sea beds. 
The next great geological development, as far as Victoria is con- 
cerned, appears to have been the appearance of the great chain of 
terrestrial volcanoes, which, as shown by Mr. A. W. Howitt, marked 
the Lower Devonian period in this country, and the ejected lava 
and ashes of which, though in an altered form, as well as the sites 
of eruption, are recognisable in the belt of igneous rocks known as 
the Snowy River porphyries. As already stated, the evidence 
obtained by Mr. Howitt indicates purely terrestrial conditions as 
having accompanied the development of this group, and it may in 
consequence bo inferred that the land was more elevated above sea- 
level then than it is now, as the terrestrially-formed felsitic ash 
beds of the Snowy River group can bo traced to within a very 
slight vertical height above the existing sea-level. That the 
mountains atlaincd a far greater altitude than now and have been 
subsequently worn away is evident, if such points as the Cobberas, 
6,000 feet high, be hut the denuded stumps of the ancient volcanic 
cones. This volcanic chain probably resembled, on a smaller scale, 
that now in action in the Andes of South America. Its position 
is, worthy of notice, aS it includes portion of the present Cordillera, 
and extends southward from where the latter now diverges sud- 
denly to the west at Forest Hill directly in the line of prolongation 
of the general course of the Cordillera through New South Wales 
from Mount Kosciusko to Forest Hill, and the general bearing of 
the chain from Forest Hill to the mouth of the Snowy would, if 
produced, run through Tasmania. Whether the crest of the land- 
surface which once couuected Australia with Tasmania was on 
this line or further to the westward is a matter of speculation, but 
it does not appear unlikely that the igneous belt extended to Tas- 
mania, either as a wholly terrestrial or partially marine chain of 
volcanoes. If t ho former, the connexion as a land surface was 
probably severed by denudation early in Middle Devonian times. 
It would be interesting to ascertain whether, in the older igneous 
rocks of Tasmania, the same evidences are observable as -those 
which justify the conclusions arrived at by Mr. Howitt as to the 
origin of the Snowy River belt of porphyries. 
The development of this group must have been the work of an 
immense lapse of time, and it is very likely that, durin" that 
period, none of the existing area of Victorian land surface was 
under water, so that there was no contemporaneous marine deposit 
in process of formation within that area, but rather a removal of 
material by the action of littoral, tluviatile, and very likely, 
terrestrial glacial denudation, and the erosion of deep troughs and 
