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ANNIVERSARY ADDRESS. 39 
"to the interesting discussion which followed is given below. He 
contended that the Hawkesbury Sandstone was of AXolian origin, 
and analogous to the recent and Pliocene blown sands of Double 
Island Point, one hundred miles north of Cape Moreton, and the 
Pliocene sands of the southern coast of Victoria and South Aus- 
tralia. In the Queensland example the A#olian sand rock is up 
to two hundred feet thick, and the angle of dip of the current- 
bedding is stated to be frequently as high as 30°. 
Mr. C..S. Wilkinson, however, in discussing this paper, stated 
that the highest angle of dip he had ever observed in the current- 
bedding of the Hawkesbury Sandstone was 264°, and that the 
prevailing angle of dip was only 20°. This, he considered, was a 
strong argument against the AMfolian origin of the Hawkesbury 
Sandstone. Mr. Wilkinson also pointed out? that some of the 
pebbles in the Hawkesbury Sandstone were as much as six inches 
in diameter, and ‘‘may have been derived from the Hartley Ranges.” 
The Rev. J. E. Tenison-Woods considered that the rounded 
character of the sand grains was characteristic of air-worn rather 
than of water-worn sands, and he compared them with the ‘millet 
seed ” sand grains of the Triassic Rocks of Europe. He accounts 
as follows for the sparkling of the sandstone when viewed in sun- 
light®?:—‘“‘ When seen under polarised light someeof the larger 
fragments (of quartz in the Hawkesbury Sandstone.—T. W.E.D.) 
would manifest their compound character, and by watching the 
effect of the light as the nicol prisms were revolved, the forms of 
the rounded grains embedded in transparent silica could be made 
out.” He subsequently gave up the theory as to the Afolian 
origin of the Hawkesbury Sandstone in favour of a tuffaceous 
origin. The latter theory is, I think, in part correct as applicable 
to some of the Narrabeen beds in the Hawkesbury Series. 
A short popular description of the Blue Mountains has been 
written by Dr. J. E. Taylor. Although many of the statements 
are open to question, the following passage may be quoted as 
1 Op. cit., p. 94. 2 Op. cit., p. 95. 3 Op. cit., p. 65. 
