GLACIAL GEOLOGY OE COIM ALAI. 
327 
slightly more easterly than in the former localities. This slight 
difference is, however, of no great moment, as we have reason to 
believe that it was due to merely local circumstances in the contour of 
the country. 
In these districts traversed by Messrs. Sweet and Brittlebank and 
ourselves, the scored rock surfaces — roches moutonnees — have now 
been observed over a distance of about fifteen miles, measured across 
the direction of the ice-flow, and it is not unreasonable to believe that 
the ice was continuous over this area. 
The well known scored rock surfaces at Hallett’s Cove, Adelaide, 
indicate that the ice causing them moved from the south to the north. 
Mr. Jack satisfied himself that such was the case in 1891, and dis- 
cussed the possibility of an Antarctic ice-sheet having reached the 
Australian shores. TTp to the present time of writing this paper, the 
age of the glacial deposits and scored surfaces at Hallett’s Cove has 
not been determined. Professor Tate inclined to the opinion that 
they were Post-Miocene, but the evidence adduced in support was not 
conclusive. We have not visited Hallett’s Cove, but we are strongly 
tempted to think that the glacial deposits in South Australia will turn 
out to be coeval with the Victorian ones. The fact of the ice having 
moved from south to north is one of the most interesting discoveries 
in Australian geology, and the honour of first noting it in the Bacchus 
Marsh district must rest with Mr. Brittlebank. 
GENERAL OBSERVATIONS. 
We are of opinion that the facts of glacial geology observed by 
us in this district point conclusively to the action of a sheet of land- 
ice, which moved in a general north-easterly direction, and probably 
reached as far north as Herrin al at least, where the motion of the 
ice-sheet, as shown by Dunn’s Rock, is from south to north. That a 
subsidence of the land surface took place when the ice-sheet- had 
reached its maximum extension seems required to account for the 
stratified beds already referred to ; in fact, there would appear to have 
been oscillations of level, phenomena similar to which obtained during 
the Pleistocene Ice Age. 
In dealing with the glacial beds of Bacchus Marsh and Coimadai, 
it must be remembered that the localities in question are probably 
very distant from the line of farthest extension of the ice-sheet, where 
the terminal moraine of greatest dimensions would iu general be 
found. Iff a terminal moraine existed, as it most probably did* traces 
of it may yet be found underlying the later formations to the north of 
Derrinal — perhaps considerably to the north. 
This absence of terminal moraines may be urged in opposition to 
tire theory of the land-ice-sheet. It should, however; be borne in mind 
that the magnitude of morainic accumulations depends upon two 
main factors: Pirst, the quantity of' material available for transport; 
and, secondly, the length off time during which the front of the ice- 
sheet remains stationary. With respect to the first’ condition nothing 
definite can be affirmed, but even supposing that a large supply of 
material available for morainic purposes did exist, yet, if the ice-front 
terminated! in water of sufficient depth to permit the icebergs to float 
off to lower latitudes with their accumulated rock-debris, the terminal 
moraine might be insignificant or even absent 
