68 
Geology and Physical Geography: 
Considering that the materials constituting the Upper Palaeo- 
zoic sedimentary deposits must have been derived from the waste 
of a land surface, and that that land surface was evidently, 
especially in the case of the eastern group, at no great distance* 
it appears far more likely that the mountain masses in the central 
and eastern parts of the colony, between the heads of the 
Macalister and Mount Ararat, between Snowy Bluff and Mount 
Tambo, and eastward from Mount Tambo, were very much 
higher than now, and projected above the ocean, by whose waters 
the Upper Palaeozoic layers were deposited in the open sea or iu 
the deep inlets thereof. 
I do not, therefore, believe that the present Main Divide in its 
central portion, between the head of the Macalister and the 
meridian of Melbourne, was ever covered by the Upper Pataozoic 
rocks, but it is nevertheless most likely that they flanked the 
southern slopes of the mountain mass, and overspread the entire 
area from the Grampians round to near Wilson’s Promontory. 
Possibly Australia and Tasmania were then separated by the 
ocean, and the Upper Palaeozoic layors overlaid Wilson’s* Pro- 
montory and the South Gippslaud country, and thus formed a 
continuous flanking deposit from the Grampians to the Macalister, 
but I am nevertheless inclined to believe that a great elevated 
ridge of granite and Silurian rocks still existed, either above 
water or only slightly submerged, extending from the Main 
Divide approximately on the direct course of the Southern Spur 
from Mount Baw Baw to W i Ison’s Promontory, and thence to 
Tasmania. This ridge may have been already somewhat lowered 
by denudation in the region now occupied by the South Gippsland 
Ranges, and over that portion, if anywhere, flowed the waters of 
any strait that may then have separated Australia from Tasmania. 
Whatever their geological relation, and that is very close, if not 
identical, the Grampian sandstones and (he rocks of the eastern 
area are geographically distinct groups, and show very clear 
evidence of a difference in (he conditions of their modes of deposit. 
The fine to moderately coarse arenaceous character of the 
Grampian sandstones, (he scarcity of conglomerate hands, and the 
well water-worn character aud comparatively small size of the 
pebbles, where they do occur, coupled with the geographical rela- 
tions of their beds to the older rock masses, all tend to indicate 
that they were deposited at some distance from the coast line of 
the period iu a wide open sea, which then covered a vast area to 
the north, south, and west. They were deposited against the 
western, southern, and, possibly, also the northern, flanks of the 
great central Lower Palaeozoic mountain mass, which had not 
been then so much denuded as we now see it, and which projected 
above the ocean of the period. The eastern edges of the Gram- 
pian beds, which rested immediately against the older rocks, and 
