138 ALEX. L. DU TOIT. 



sidered and plotted, figures that appeared in any way 

 doubtful having been omitted : for example, all shallow bores 

 were excluded in considering temperature increments. 



Though the writer's personal knowledge of the area is of 

 the slightest, his interest in the problem, principally by 

 reason of certain analogies with South Africa, must serve 

 as an excuse for the contribution; moreover, the magnitude 

 of some of the actions in dispute, such as the effect of gas, 

 can be closely determined, the probable rates of flow 

 through the water-bearing beds can be estimated roughly, 

 while there are particular aspects of the question dependent 

 upon pressure, temperature and salinity that deserve to be 

 set out and indicated in detail. 



The hydraulic departments of the several States con- 

 cerned are clearly alive to the importance and urgency of 

 the solution of the problem, especially in connection with 

 control of the supplies now and in the future, but, as Mr. 

 Knibbs pointed out in 1903, x our knowledge of the physics 

 of the basin in its earlier and almost untouched condition 

 is very slight. Now, though data are rapidly being col- 

 lected, the equilibrium of the reservoir has been entirely 

 upset, and this disturbance from the original condition is 

 making the solution of the problem more and more difficult 

 owing to the falling pressure in bores, to their mutual 

 interference, and to leakage, with consequent reduction of 

 yield. The potential surface is in a state of flux, the 

 accurate determination of the isopotentials over the entire 

 region for any particular short period is a practical impos- 

 sibility; accordingly deductions drawn from their position 

 and shift are likely to be only partially correct. 



In utilising the published data for the preparation of the 

 attached maps, it must be explained that considerable dis- 

 crimination had to be used and much material rejected, by 



1 G. H. Knibbs, this Journal, xxxvu, p. 24 -47. 



