64 
president’s ADDRESS — SECTION c. 
owing to their having been dropped in heaps from the floating roots 
of trees, but much more likely from floating ground-ice. Large 
isolated boulders of granite, &c., occur here and there in the midst of 
strata of fine sandy or muddy material. These could hardly have been 
brought to their present positions except by glacial action. Portions 
of trunks of coniferous trees are occasionally found lying horizontally 
in the strata.” 
I am informed by Mr. E-. L. Jack that some of the largest of 
these blocks are of the capacity of about two cubic feet, and they 
are for the most part angular or sub-angular. 
In 1870 Mr. C. S. Wilkinson, the late Government Geologist of 
New South Wales, recorded what he considered to be evidence of 
glacial action in the Triassic Hawkesbury series of New South 
Wales* : — 
“ In the Hawkesbury sandstones, which are over 1,000 feet in 
thickness, there are occasional intercalated beds of clay shale of a 
lenticular character, having a maximum thickness of perhaps 15 to 
20 feet. 
“ The shales contain small fragments of ferns, especially 
TJiinnJeldia odontopteroidcs Mr. Wilkinson states (op. cit. } p. 100): — 
“In the sections exposed in the quarries at Port Macquarie, 
Wooloomooloo, Flagstaff Hill, and other places, may be seen angular 
boulders of the shale of all sizes up to 20 feet in diameter, 
embedded in the sandstone in a most confused manner, some of them 
standing on end as regards their stratification, and others inclined at 
all angles. They contain the same fossil plants that are found in the 
beds of shale from which they have evidently been derived. These 
angular boulders occur nearly always immediately above the shale 
beds, and are mixed with very rounded pebbles of quartz ; they are 
sometimes slightly curved as though they had been bent while in a 
semi-plastic condition, and the shale beds occasionally terminate 
abruptly as though broken off. Had the boulders of soft shale been 
deposited in their present position by running water alone, their form 
would have been rounded instead of angular. It would appear that 
the shale beds must have been partly disturbed by some such agency 
as that of moving ice, the displaced fragments of shale becoming 
commingled with the sand and rolled pebbles, carried along by the 
currents. Occasionally in the beds above those which contain the 
angular boulders occur a few rounded pebbles of shale, showing that 
the currents had swept along for some distance a few of the angular 
fragments until they had become rounded. These pebbles are usually 
oval in shape, and are embedded in such a manner that the longer 
axis of the pebble is nearly always inclined or dips towards^ the 
S.W., thus indicating that the transporting currents had come from 
that direction, whereas the angular boulders in the beds below are, as 
before mentioned, confusedly heaped together without regard to size. 
These boulder accumulations occur in irregular patches apparently 
throughout the Hawkesbury series. Besides in the places already 
mentioned they may be well seen in the railway cuttings on the 
Blue Mountains, especially about Katoomba and Mount! ietoria,” &c. 
* Jour. Roy. Soc. N.S. Wales, vol. xiii., 1870. “Notes on the Occurrence of 
Remarkable Boulders in the Hawkesbury Rocks,” pp. 105-107. 
