BY W. N. BENSON. 493 



and foothills which separate the plateau of New England from 

 the Western Plains, and their long southward extension, known as 

 the Liverpool Plains. 



The main river in the area is the Namoi, which, leaving the 

 plateau by a rugged gorge, flows directly through the foothills out 

 on to the Liverpool Plains. It receives, as tributaries, the Peel 

 River from the south, and the Manilla from the north, both of 

 which have followed a semisubsequent course in the slope, and the 

 latter of which has several markedly obsequent subtributaries. To 

 the north, the main river is the Gwydir, which also leaves the 

 plateau in a gorge, and passes directly on to the Western plain, 

 being joined by subsequent tributaries, such as the Horton River 

 and Hall's Creek. The evolution of this drainage-system is most 

 complex. 



From Warialda, in the north of the area, to Tamworth, is about 

 100 miles, and 30 miles further, in the same direction, bring one 

 to Nundle, the southermost township in the area studied. The ser- 

 pentine line extends this whole length, and has been reported, at 

 various points, for about 40 miles still further to the south. These 

 last occurrences have never been studied geologically. There can 

 be little doubt that the belt extends also north of Warialda, but 

 it is there covered by Jurassic sandstone. It may, however, be 

 stated with confidence, that this great feature is not far short of 

 200 miles in length, and runs nearly straight in a direction about 

 20° west of north. It divides the region into two sharply dis- 

 tinguished portions, there being seldom much difficulty in deciding 

 whether a particular specimen has been derived from the eastern 

 or the western side of this line. (Certain exceptional rocks and 

 localities, where confusion may arise, will be described later.) To 

 the west of the serpentine-line, the rocks consist of radiolarian, 

 banded cherts, limestones and tuffs, with bands of spilite-lava in 

 the lower horizons, of heavy agglomerates, or fine-grained mud- 

 stones in the middle horizons, passing up into very distinctive con- 

 glomerates. Near the serpentine-line, they are always steeply 

 inclined, generally with an easterly dip, but further away, i.e., from 

 five to ten miles to the west of the line, they may be less highly 



