_ 80 ' THE HAWKESBURY SANDSTONE. 
leaves but a slight film upon the surface of the ground where it 
if this be so, one cannot but be amazed at the length 
of time required for the sub-aerial sifting of the material and for 
the transport from the dry central regions of Asia of that finest 
dust with which ‘so large a portion of China eventually became 
covered, to a depth varying from 50 to 100 feet up to 2,000 feet.” 
Perhaps it is not entirely such a formation as this with which 
we have to deal in the Hawkesbury sandstone. Oursisa 
area possibly not wholly like that of the Desert. It is no use at 
present encumbering ourselves with speculations as to whence this 
d derived. A very diligent and long continued examination 
of the constituents of the rock, taken from a very great number of 
places, and a better acquaintance with the physical characters of 
the older formations, will alone throw light on this question. We 
must not suppose either that the surface was wholly devoid of 
vegetation. If we remark how very little if any of the aren 
o man 
sll be inclined to think that the land around was a desert like 
Arabia, in which stand storms would be numerous and the accumt 
lation of dust rapid. After the upheaval of the Permian strata 
the area may have been a desert region in which a few coal plants 
survived, A dry climate caused a rapid sprees pee 
and the accumulation of aerial sands. I do not preten 
the Permian 
and may have 
plant remains 
that the upheaval took place immediately after 
period, but that it was not previous to that time, 
n as late as the Cretaceous. The evidence of the 
is as yet insufficient to establish any period. 
Stratified rocks not all aqueous.—At one time every formation 
not obviously fresh-water or intrusive was hastily concluded to have 
been. derived from the sea, whether it contained marine» remains 
out direct evidence than we are in Pier ei them ial 
any marine area where the dredge brought up only Pp pt 
and vegetable shale with sand destitute of lime and Physi 
rounded pebbles. Mr. Selwyn, in his Notes on the = 
Geography, Geology, &e., of the Colony of Victoria,* se rocks 
absence of marine fvieile from the lowest beds _ the mioce Onl characte oe 
of Reger: pay amet beds of evidently te ee pew i = 
This calls a marine gravel. It is a wid 
= rspne of the Intercolonial Exhibition Catalogues published nl a 
