ARTESIAN WATER IN N. §. WALES AND QUEENSLAND. 413 
land is known as the Rolling Downs Formation. This formation 
covers about 62,000 square miles in New South Wales, as estimated 
by Mr. E. F. Pittman, a.n.s.m., the Government Geologist, and 
the enormous area of 376,832 square miles in Queensland, equal 
to over fifty-six per cent. of its total superficial area, as calculated 
by Mr. R. L. Jack, F.a.s., the Government Geologist. Out of 
this area of Rolling Downs Formation in Queensland 88,300 square 
were considered by Mr. Henderson in 1893 to have been proved 
to contain artesian water, and in New South Wales artesian water 
has been proved to exist at intervals over an area of about 20,000 
square miles. 
In Queensland the estimated total capacity of outflow of all the 
wells was quoted by Mr. Henderson in 1893 as 105,000,000 
gallons daily ; amounting to 38,325,000,000 gallons per annum.* 
In order to replenish this volume of water an amount of rainfall 
would need to percolate equal to twenty-nine inches per annum 
over an area of ninety-one square miles. 
Mr. Henderson estimates that the aggregate breadth of the 
outcropping edges of the water-bearing beds of the Lower Cretace_ 
ous are not likely to be more than a few chains, and on the 
assumption that the average width is ten chains, and the length 
1,600 miles (measured from the boundary between New South 
Wales and Queensland to the northern limit of the beds in about 
Lat. 18° South, and including the western edges of the Rolling 
Downs Beds on the flanks of the McKinlay Ranges) Mr. Henderson 
estimates that the total superficial area of the porous beds of the 
Cretaceous Formation in Queensland available for intake does not 
exceed perhaps two hundred square miles. He adds (Joc. cit. p. 5), 
‘“‘ Tf the basis of this simple computation is correct ; if the supply 
is not greatly supplemented by water percolating through the 
surface strata on the hill sides immediately above the several out- 
crops and by streams that cross them, and if the number of wells 
* Queensland Water Supply—Report of the Hydraulic Engineer to the 
Honourable the Colonial Treasurer, Brisbane, 25th January, 1893. 
