48 THE GEELONG NATURALIST. 
striated and groved pebbles and boulders, stamp the conglome- 
rate as, undoubtedly, of glacial origin. The source of the 
material must have been vast, as the conglomerate includes an 
almost infinite variety of rocks and minerals, granites, syenites, 
gneisses, schists, quartzites, metamorphic sandstones, slates, 
shales, conglomerates, breccias, porphyries, quartz, jaspers, &c., 
appear in endless confusion. Mr. Dunn also describes the beds 
of sandstone mentioned in our last issue, and is equally certain 
that they are intercalated between the several layers of the 
conglomerate. The presence of this sandstone indicates that 
the material was, in all probability, deposited from icebergs into 
water, and during the intervals of deposit currents of water had 
brought in layers of sand. The deposit is at its highest part 
at least 700 feet above the sea-level; hence, if the deposit took 
place under the sea, a very great change in the level of the 
country has occurred since. Mr. Dunn is of opinion that the 
deposition took place over level country, and before the Main 
Divide was elevated into a mountain range; and, indeed, there 
is much to support this conclusion. Similar deposits occur 
near Bacchus Marsh, and these are found in many places greatly 
faulted and disturbed, which indicates that they have been 
subjected to great pressure. Such pressure would be supplied 
by the thrusting up of the Main Divide. The probable manner 
of deposition is clearly indicated : “ Icebergs that started their 
career as glaciers alone would account for the phenomena pre- 
sented by this conglomerate. The glaciers would, while gliding 
down their native valleys, accumulate in their mass vast quanti- 
ties of earth, sand, clay, stones, pebbles, and masses of rock 
from the sides of the valley, and from the branch valleys 
running into it. As they pushed out into the ocean or lake 
they would become detached, and were then driven by wind 
and current to the site of the present conglomerate; as they 
floated over or became stranded, the melting of the ice would 
set free the included rocky or earthy matter, which would fall 
to the bottom, and just in such manner as sections of the 
conglomerate expose.” 
The presence of the erratic blocks tends to confirm this 
conjecture of the origin of the formation. 
The publication of the notes, which are accompanied by a 
map of the locality and some excellent views from photographs 
taken by Mr. A. W. Howitt, is, altogether, the most scientifically 
interesting that has been issued by the Mining Department for 
a very considerable time. 
