PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 191 



shown that the falling off of B would have been much higher 

 had A been overdrawing the supply, one must conclude 

 that interference is not yet marked, and that the falling 

 off in yield is due rather to a universal lowering of potential 

 over the region. 



Calculations based on underground velocities of 4 and 6 

 inches per day, give the volume passing into A as between 

 30 and 40 millions daily, and that into B as from 16 to 20; 

 although only approximations, these figures serve to give 

 a general idea of the magnitude of the quantities involved, 

 and fit well with the conclusion stated above. Upon tabu- 

 lating the results within a square degree of country around 

 Blackall in Queensland, similar conclusions were reached. 



That the lowering of head is general rather than local is 

 indicated by the fact, that the hydraulic gradient calculated 

 from bores now sub-artesian but originally flowing, may 

 correspond exactly with that obtained from the still flowing 

 wells, for example at Winton (II, §246); therefore the 

 duplication of bores is generally no remedy for loss of head 

 not due to leakage or obstruction. 



The increases in yield of a few bores, e.g., Neargo and 

 Oollymongle in the Moree district, are in strong contrast 

 to the almost universal reduction as shown by the records 

 of the several Hydraulic Departments, and which the Inter- 

 state Conference has found to be proceeding at a progressive 

 rate — in New South Wales between 1903-8 at about 5J-% 

 per annum, and for 1913-4 at about 8% — thus bearing out 

 Gregory's 1 contention for the necessity of the restriction 

 of flows by legislation or otherwise. In view of the import- 

 ance of the recommendations made by the members of the 

 Conference, 2 it is needless to say more, except to express a 

 hope that they may be given effect to as soon as possible. 



' J. W. Gregory, Journ. Roy. Geogr. Soc, Vol. 38, p. 88, 1911. 

 2 II, pp.. xii- xv. 



