Te 
440 T. W. E. DAVID. 
described by Professor Tate of Adelaide as formerly occupying 
large areas of Central Australia, inasmuch as these lakes were of 
Tertiary Age, whereas the age of the strata yielding the artesian 
water was Lower Cretaceous. As Mr. Knibbs had pointed out, 
neither expansion of the artesian water nor of the associated strata 
consequent on increase of temperature at a depth, could raise the 
hydraulic grade of the artesian water. The expansion of the 
strata would be irresistibly powerful, and would force the artesian 
water once it had filled the water-bearing strata back towards the 
intake, but once the expansion had taken place it would be subject 
to fluctuations so slight as to be practically a negligible force in the 
dynamics of artesian water. If the pressure of the artesian water 
of New South Wales was hydraulic and not hydrostatic, then the 
expansion of the water as it descended to lower levels by gravita- 
tion would perhaps help towards increasing the pressure, but only 
to a slight degree. The theory that the artesian pressure was 
due to secular contraction of the earth’s crust compressing sealed 
beds of deep-seated water-bearing sands was open to the following 
objections :—(1.) The Lower Cretaceous water-bearing beds had 
been folded, only to a very limited extent, over the vast areas 
where they had hitherto been geologically examined in Australia, 
so that the segments of the earth’s crust, where they had been 
deposited, could not be held to have been materially shortened 
since the Cretaceous Period. (2.) Had the shortening and com- 
pression been material, the pressure it would have exercised on 
the water-bearing beds would again have been irresistibly strong, 
and would have come on too gradually to account for the continu- 
ous flow of water from the mud springs throughout a large portion 
of the Tertiary and probably the whole of Post-Tertiary Time. 
In his opinion the chief question at issue was, is the supply of 
artesian water hydrostatic or hydraulic? In his opinion it was 
probably hydraulic, the deep-seated water flowing sea-wards as 
already explained, as through an inverted siphon. The central 
portions however of the basin must be practically hydrostatic. No 
other hypothesis seemed to account satisfactorily for the freshness 
