204 



"For the past ten years, upon the assumption just referred to 

 the discharge of the Darling River (at Bourke) has been taken 

 .as a percentage of the rainfall, and the yearly amount has varied 

 from 5-81 to 0-09 per cent., the mean for the ten years being 

 1'46 per cent., a startling result, and one which I believe to be 

 without parallel in any country in the world. ... In 

 Europe 20 to 50 per cent, of the rain flows away in the rivers, 

 in England about 30 per cent., and here in a river— the Murray, 

 with similar basin and rainfall to the Darling — 25 per cent, of 

 the rain flows down the river. . . . When we go into figures 

 to see how much it is, we get a surprising result, viz., that it is 

 not less than ten times, and probably 16 times what the river now 

 ■ carries away." — Journal of Royal Society, N.S.W., 1889, part 1, 



Vol. XX ni. 



I propose to deal in this paper with the vv^estern portion of 

 the basin, as delineated roughly on the chart, which for purposes 

 of reference, I subdivide into the Menindie basin, the Topar 

 basin and the Cuthawarra basin. My deductions of an unlimited 

 supply of water are based on an examination of the wells sunk 

 within these areas. Beginning with the Menindie basin, as 

 nearest to Broken Hill, of its southern extension it is difficult to 

 say more than already described, but the wells Middle Camp, 

 Eaglehawk, North Ita on the Netley Run, and AVanga on the 

 Burta Run, are all of the same general character, 200 feet and 

 over before reaching the diift-sand which contains the w^ater ; 

 of these the Wanga Well is the most western within the 

 basin. The other wells Jiitherto sunk on Burta have been in the 

 southern projection of the older rocks, where they gradually sink 

 under the more recent formation, towards the Older Tertiaries as 

 represented by the Murray clifls. Speaking of the Menindie 

 basin generally we may expect to find the centre of the depres- 

 sion, or rather its greatest depth, somewhere about the great 

 lakes, not only because they occupy the lowest part of the present 

 plain, but also because of their distance from the ancient rocks. 

 On the other hand, the two semi-detached areas, whether viewed 

 as separate from or as extensions of tlie main area, are probably 

 the shallowest ; for our purposes this does not much matter, as 

 the Menindie basin measures 140 miles across, and from the 

 absence of any outliers of the Archyean rocks whatever (cer- 

 tainly no traces have yet been found), we are justified in treating 

 it as a whole, within whose boundary unlimited supplies of sub- 

 terranean water exist. 



The accompanying map, which sketches in approximately the 

 boundary of the Arch&ean rocks and the Tertiary basin, is com- 

 piled from the official geological map of ISTew South Wales, 

 published by the DejDartment of Mines in 1877, and from 



