36 T. W. E. DAVID. 
The Rev. W. B. Clarke, F.r.s., ascribes a thickness of from 
eight hundred to one thousand feet to the Hawkesbury Sandstone, 
and states that on the summit of the Blue Mountains, and along 
the Grose River, the thickness of the series is very much greater 
than near the sea.’ 
The following statements by Mr. C. 8. Wilkinson, the late 
Government Geologist of New South Wales,* bear directly upon 
the subject under discussion :—‘ It would appear that the coal 
measures had been upheaved and partly denuded, and that in the 
shallow freshwater lakes which filled the depressions, the shale 
beds were deposited. Then succeeded a subsidence of the land to 
sea-level, and the area in which the Hawkesbury Sandstones were 
laid down became a tidal estuary, mostly of freshwater. 
The current bedding dips in various directions, but it is chiefly 
so the north-north-east, as thovgh the prevailing currents came 
from the south-south-west. After the Hawkesbury deposits had 
attained a thickness of about 1,000 feet, they were upheaved and 
a freshwater lake was formed, in which accumulated the muddy 
sediment of the Wianamatta series. Thus, from the Middle 
Coal Measures to the Wianamatta series inclusive, the strata 
amounting to about 5,000 feet in thickness, are of freshwater or 
estuarine origin; and with the exception of the upheavals or 
oscillations of level referred to, this part of Australia must have 
presented land features from the Carboniferous period of the 
Paleozoic era to the Wianamatta of the Mesozoic. 
Mr. ©. S. Wilkinson, also states in another place,® ‘ The vast- 
ness of the depth and extent of the precipitous gorges and valleys 
of the Blue Mountains inspire one with feelings of silent awe and 
wonder, and impress the minds of some persons with the notion 
we hear so frequently expressed, that such enormous ravines in 
1 Remarks on the Sedimentary Formations of New South Wales, by 
the Rev. W. B. Clarke. | Fourth Edition, Sydney, 1878, pp. 70 - 71. 
2 Mineral Products ete. of New South Wales, Sydney 1887, p. 79. 
3 The Guinn’ Guide of New South Wales, ‘Third Edition, ». 127. BY 
Autbority, “ydaey, 1886. 
Resnick 
