178 ALEX. L. DU TOIT. 



Firstly, it is clear that in almost every case the pressure 

 of the supply has increased with depth until the impervious 

 floor has been reached. In New South Wales a great pro- 

 portion of the bores have been sunk to bed-rock, but in the 

 other States, this is the exception, and for this reason the 

 figures for the static pressures cannot, and do not, represent 

 the truth, though in many cases no doubt they are certainly 

 but little lower. 



Secondly, the serious leakage brought about by closing 

 down bores, has prevented the taking of further periodical 

 gaugings satisfactorily in a number of cases. 



Thirdly, many private bores have never been tested, 

 either through lack of opportunity, or because of the risk 

 involved. Some idea, however, can be gathered as to their 

 static pressures, from their yield in relation to their depth 

 and diameter of casing. The friction developed during the 

 flow represents a loss of head that is very considerable in 

 the deeper holes, as shown by Table B, and by its means a 

 minimum value for the static head can be obtained ; the 

 latter will exceed this by an amount depending on the 

 porosity of, and depth into the water-bearing beds as will 

 be discussed later on. 



Fourthly, the presence of gas, as proved already, may 

 raise the pressure considerably. 



Fifthly, the data published in the two Interstate Reports 

 are frequently incomplete ; figures for the pressures are 

 given that range between two very different values — in 

 such cases the mean has been taken — while no doubt there 

 are some inaccuracies. In re-plotting the Coonamble- 

 Moree area from the data given in the Second Report, 

 totally different values were often found to those marked 

 on the Isopotential Map (plates 13 and 1 4). It is not clear, 

 whether in the preparation of the latter, any pressures not 

 in harmony with those of the adjoining bores were ignored 



