MEETINGS OF SOCIETIES. | 191 
in many places by the Wainamatta beds, and by igneous rocks. 
In no place is there sign of upheaval, but at the first Zigzag are 
numerous signs of a downcast or fault. False-bedding is the 
characteristic feature of the formation in nearly every portion. 
There are two distinct forms of stratification—one which makes 
the main lines of subdivision, dividing the stone into massive 
layers of varying thickness, the spaces between the layers being 
often filled with a fine-grained dust, or by red bands of ironstone ; 
and between these are fine lines of stratification which are mostly 
inclined to the horizon. The fossils are mostly composed of the 
roots and stems of plants. As a whole, the beds are from 800 to 
tooo feet thick, and contain, in addition to the plant remains, 
patches of shale or coal, and occasionally fishes of at least two 
species. From a consideration of their whole structure and con- 
tents, the author concludes that the formation has been formed 
by wind, and he inclines to the opinion that the land from which 
it was derived was a desert like Arabia, in which sand storms 
were numerous and the accumulation of dust rapid. This view 
is strengthened by the examination and comparison of eolian 
rocks in various other parts ofthe world. Theinterior of Australia 
is now in many parts composed of a desert region, with shifting 
sand hills, tresh and salt marshes and lagoons, and when the 
waters dry up, as often happens, fish, etc., are left entombed in 
the salt. The conditions, then, requisite for the formation of 
such a deposit as the Hawkesbury sandstone are all to be found 
still in Central Australia. The appearances which have been 
attributed to ice-action are believed by the author to be the 
remains of creeks and streams which flowed among the loose 
sandy hillocks, and exercised a great denuding action, especially 
when in flood. ‘The results of the essay are summarised thus :— 
1. That the Hawkesbury sandstone is a wind-blown formation, 
interspersed with lagoons and morasses, with impure peat. 2. 
That there has been no upheaval, but rather a subsidence, 
which probably extends from the base of the range to the sea. 3. 
That the peculiar lamination of the beds is due to the angle at which 
dry sand slips and rests when blown by the wind. 4. The beds 
of ironstone represent vegetable matter destroyed in oxidizing the 
iron, and this is why so few plant remains are tound. 5. The 
irregular layers of the sandstone formation probably represent 
what was a tranquil portion of the surface for a time, on which 
there may have been a vegetable growth now represented by iron- 
stone bands. 6. The smaller gravel may be wind-blown; the 
larger may have been derived trom creeks. This is also the origin 
of the fragments of shale. The creeks have undermined them and 
broken them up. 7. Conglomerates may have been derived from 
stony deserts, such as we have in the centre of Australia. They 
represent all the stones of a sandhill district from which the sand 
has been blown away. 8. The precipitous cliffs of the Blue 
Mountains are the hard central cores of sandhills, the loose por- 
tions of which were easily blown or washed away. g. That in all 
respects the sandstone is like many desert formations otf the 
interior. 10. Thata large arid or desert region has existed in 
Australia in mesozoic times, while to the north and north-west 
there was a cretaceous sea. 11. That this desert was terminated 
by the outpouring of vast quantities of volcanic rock, which altered 
