BY H. I. JENSEN. 57 1 



or other noxious herb, which completely monopolises the plains 

 for the season, and only dies out to give the monopoly to a plague 

 of something else. The winds bring the seeds from the west. 

 The rabbit also helps the invader by shunning it for a while, and 

 feeding on the diet he is used to. It is due to the rabbit 

 that prickly species of thistles, unsuited for feed, are getting the 

 upper hand .on the plains. 



The sandy soils of the Pilliga Scrub are, I am told, very deep 

 in places, and must have been deposited partly by the aid of 

 water in the rainy period, and partly by wind-action in the 

 present arid cycle. 



A striking instance of natural pruning is seen, throughout the 

 Pilliga Scrub, in the uniform height above ground of the lowest 

 branches of the pine forests. 



Black soil plains are often devoid of forest trees. This is due 

 mainly to the fact that they tend to become swampy in wet 

 weather, and to scorch up, cake and crack in dry weather. 

 Where the black soil is loamy, such trees as box {Eucalyptus 

 Woollsiana T), silver-leaved ironbark {Eucalyptus melanoiyhloia), 

 kurrajong, wattles and myalls are common. 



4. Geomorphogeny. 



(a) F re-Cretaceous Configuration. — The Warrumbungle area 

 was probably submerged in Carboniferous times, being the 

 western margin of a sea which stretched across to the New Eng- 

 land border. Elevation followed. In late Permo-Carboniferous 

 times parts of it, especially the eastern and southern quartants, 

 were depressed, and received sandy and gritty sediments (the 

 Upper Coal Measures) probably from the west. In Triassic 

 times the whole area was again submerged. The subsidence 

 continued, with interruptions, until in Cretaceous time a move- 

 ment of elevation or negative movement of the sea, probably 

 connected with a general uplift in the Liverpool Range and New 

 England, again made the area dry land. This uplift gave the 

 Triassic sediments a N.N.W. dip, just as the uplift of the New 



