148 E. C. ANDREWS. 



of broad shallow valleys excavated in the more basic 

 members only of the series, being connected with broad 

 upland valleys and plain-like surfaces in the less resistant 

 rocks in the vicinity. In the more acid members of the 

 granites, the Stannifer level is confined to narrow, mature 

 valleys or even to gorges at the extreme head- waters. At 

 times also this trangresses the margin of the acid granites. 

 The average height of the level is about 3,250 feet, and of 

 its more central mature valleys about 2,900 or 3,000 feet. 

 Tenterfield and Deepwaterlie on such mature valley bases 

 excavated in the general level of the Stannifer Plain. About 

 200 or 300 feet above this, say at an average height of 

 nearly 3,600 feet, distinct traces of another but dissected 

 level are common. Examples of such residuals are the 

 Main Mole Tableland, the plateau west of Bungulla Siding, 

 Poverty Point, Boonoo Boonoo, and other places. Above 

 these levels again rise other fairly large sub-horizontal 

 areas varying from 3,750 to 4,000 feet in height, and such 

 areas may be seen near Tenterfield, Bolivia, the head of 

 the Deepwater River and from the Cataract River towards 

 Wallangarra. A fine example occurs between the 9J and 

 the 11 mile pegs on the Tenterfield- Wilson's Downfall Road. 

 Another is suggested by the presence of accordant summits 

 rising above the 3,600 feet level in the neighbourhood of 

 Mount Mackenzie at Tenterfield. Above these sub-hori- 

 zontal surfaces in the larger acid masses again rise other 

 points varying in height from 4,300 to 5,000 feet. Such 

 are Mount Mackenzie (4,300 feet), Bald Rock (4,400 feet) 

 in the acid granites, and Mounts Jondel, Bajimba (5,000 

 feet), Oapoompeta (5,000 feet), Spiraby (5,100 feet), and 

 Cooloomangera in the acid porphyries, a little to the east 

 of Bolivia. Owing to their relatively small area and the 

 distortion of the vertical scale, these various levels, higher 

 than the Stannifer and the Sandon levels, are not clearly 

 shown on the model. 



