ARTESIAN WATER IN N. S. WALES AND QUEENSLAND. 435 
statement that there were wells at a higher level than the intake 
or source of the supply had not been proved. If the pressure of 
the water was caused by the shrinkage of the surrounding earth 
or by the generating of carbonic acid gas, the supply of water 
would be driven back towards the intake, and the pressure would 
not exceed the hydrostatic pressure, except in cases where the 
intake got blocked, in which cases the supply could not be 
replenished and would be intermittent and not continuous as in 
most artesian wells. Oil was not artesian water and the hydro- 
static pressure theory was not applied to it. The pressure was 
probably due to chemical action, that was the generating of gas. 
In most cases the pressure of oil wells was found to decrease after 
atime. The experiment shown by Professor David was very 
instructive, especially as the results were too often overlooked, 
although it was well known that where the velocity of water 
flowing through a conduit was checked (in this case by sand), the 
pressure would rise, and where the velocity increased the pressure 
would fall ; the explanation of this could be obtained from text 
books on hydraulics. 
Mr. H. G. McKinney remarked that the apparatus exhibited 
by Professor David to illustrate the flow of artesian water, made 
clear not only the ordinary features of the underground flow, but 
also the cause of the rise of artesian water under certain conditions 
to a greater height than might have been anticipated. He pointed 
out that popular opinions regarding the extent of land likely to 
be irrigated from artesian bores were generally wide of the mark. 
If the flow froma successful artesian bore were expressed in cubic 
- feet per second instead of gallons per day, exaggerated anticipa- 
tions would often be avoided. Among the highly successful bores 
there are very few which yield more than five cubic feet per 
second—that is 2,700,000 gallons per day. The area which a flow 
of a cubic foot per second will irrigate depends on a variety of 
conditions; but taking average circumstances and high class 
management, it is unlikely that that area would exceed one 
hundred and fifty acres. Hence an artesian well with the flow 
