102 



E. F. PITTMAN. 



Professor C. S. Slichter, has suggested 1 that Chamberlin's 

 condition VII should be amended to read "an absence of 

 any easy escape for the water at a lower level than the 

 surface of the well." 



The necessity for some such amendment is apparent when 

 it is remembered that some Artesian basins have leakage to 

 the sea, while in others the porous water-bearing beds are 

 intersected by valleys of denudation, thus providing an 

 escape for the water at a level which is lower than the 

 surface of the flowing wells. In these cases it is clear 

 that the resistance which the porous beds offer to the 

 lateral flow of the water is sufficient to preserve the 

 necessary head. 



With the slight amendments just referred to the conditions 

 prescribed by Chamberlin in 1885 may be accepted as 

 governing tlie occurrence of Artesian water. 



In the great Australian Artesian basin which comprises 

 considerable portions of the States of Queensland, New 

 South Wales, and South Australia, the observations of local 

 geologists have established the fact that the conditions 

 just referred to prevail. There are the porous sandstones 

 of the Triassic Coal Measures (and in places the overlying 

 Blythesdale Braystones) outcropping at considerable 

 altitudes in Queensland and New South Wales, on the flanks 

 of the Main Dividing Range, and clipping westward under 

 the central Australian plains: there are the underlying 

 impervious rocks (granites, and altered palaeozoic sediments) 

 which form the floor of the basin: there are the overlying 

 impervious strata which cover the porous sandstones to a 

 depth of several thousand feet: and, lastly, there is an 

 adequate rainfall, averaging about twenty-five inches per 

 annum, in those districts where the porous beds are exposed 



1 Water Supply and Irrigation Papers No. 67, U. S. Geol. Survey, The 

 Motions of Underground Waters, (Slichter) 1902, p. 82. 



