NOTES ON THE GEOLOGY AND WATER SUPPLY OF 



THE INTERIOR OF NEW SOUTH WALES. 



Plate XXV. 



By Rev. J. Milne Curran, F.G.S. 



The subject of water supply for the interior is occupying a con- 

 siderable amount of attention at present. Much of what has V)een 

 suggested on the subject is of no practical value from the fact that 

 comparisons are instituted with other countries where the existing 

 physical conditions are very different. The anomalies, (so called) 

 which we find so often in Australian Geology and Botany pi'esent 

 themselves in full force when we come to deal with the question 

 of a water supply for the interior. In other countries the rivers 

 grow and increase as they flow, while in the intex^ior of the colony 

 they (with two exceptions) grow less. When we study a map of 

 the Thames or Ganges we may mark the source of the river and 

 say that a spring or glacial stream comes to light at that place. 

 This is all changed in the country to which these notes refer. 

 When you stand at the point indicated on the map as the source 

 of any western river, you for the most part find no water-course, 

 no water, and can form no idea of where the water comes from. 

 When you do find a *' river " you soon learn that neither does it drain 

 the country it flows through, nor is there any soakage from the river. 

 The physical conditions of the interior are so exceptional that one 

 must be familiar with them before any scheme can be proposed to 

 meet all facts observed. The following notes refer to underground 

 waters only, and are made out altogether from personal observation. 



Underground Waters. — I take it as proved that the rainfall is 

 largely in excess of water accounted for by soakage, evaporation 

 or the outflow of rivers ; otherwise, or as Mr. Russell puts it, we 

 should expect to find at Bourke a river 200 yards wide, and 200 

 feet deep. The water gets away underground, and the geological 

 history of part, at least, of the interior will explain in what way. 

 By the interior I mean all the country situated west of Dubbo 

 and north of the 33rd parallel. In this country three well-marked 

 and distinct geological areas may be distinguished which for 

 convenience I name as follows : — 



