BY H. I. JENSEN. 567 



■east of Coonabarabraii it swings round and flows south, first in 

 a narrow deep trough, later, about 10 miles south of Coonabara- 

 bran, in a shallow bed little below the level of the plain (Rivers- 

 dale). Later, at Mundooran, the course swings to the west, and, 

 still further on at Breelong, it takes a north-westerly direction 

 which it preserves till the Darling is reached. Thus this river 

 describes a spiral course round the Warrumbungles. 



There can be little doubt that the drainage was more direct 

 prior to the volcanic outbursts. There was probably a conse- 

 quent stream draining the Liverpool Plains in the same direction 

 as the Naraoi and Macquarie. The great effusive pile of the 

 Warrumbungles, however, effectively blocked it, and a new, 

 more circuitous drainage-system had to develop. This accounts 

 for the youthful appearance of the Castlereagh as compared with 

 the Namoi. The poorness of the water-supply in the Castle- 

 reagh, and the development of monkeys (aboriginal '^ moongies") 

 in its course I have already touched upon in my preliminary note.* 

 Here, too, I mentioned how the creeks flowing westward from 

 the Warrumbungles dry up, and have beds so little depressed 

 below the general level that the traveller hardly notices when 

 he crosses a creek. The drying up of streams on reaching the 

 level country was also noticed in the Pilliga country. The water 

 coming down from the mountain springs may be absorbed by the 

 outcrop of porous artesian strata at a level of about 1,400 feet. 

 Oertain it is that the rainfall at the present day is insufficient to 

 enable the streams to erode beds, but the existence of dry water- 

 jcourses infilled with sand shows that at a remote period there 

 was a better rainfall. 



The watershed known as the Warrumbungle Range divides 

 the drainage-areas of the Castlereagh and the Namoi. It com- 

 mences as an offshoot of the Liverpool Range, east of Coolah, 

 iirst runs N.W., then W., losing itself in the Warrumbungle 

 Mountains to the N.W. of Coonabarabran; then it re-emerges as 

 the Kalga Range at Bulloway Mountain. The Kalga Range 



* These Proceedings, 190G, p.231. 



