Pacific from a "negative" central area, such as Sucks has 

 shown for Eurasia, then we may imagine the continental 

 margins as tiring overthrust against a great sub-oceanic 

 creep and the convexity of the continent to the Pacific is 

 understood. 



In this method the Pacilic would he considered as a sink- 

 ing mass which produced lateral thrusts at a depth towards 

 the continent, while at the same time there was a back- 

 ward superficial thrust of the continental shell over the 

 mass slowly advancing below the ocean floors. An able 

 and simple statement of the main mechanical principles 

 involved in such action is supplied by Chamberlin 1 and 

 Salisbury. This also is the principle insisted upon by Bailey 

 Willis in his later writings. 2 



But as will be shown anon, the presnt New Zealand Alps 

 and the Australasian mountains are not of the compressive 

 (folded) type, but are merely plateaus of the Arizona and 

 California!) or Tibetan types. 



There are moreover other points to be considered. The 

 centre of Australia has been a "negative" or sinking area 

 during various geological periods, while Western Australia 

 has been a horst ! during the greater part of geological time. 

 The southern periphery of Western and South Australia is 

 concave to the Southern Ocean, while the neighbouring 

 Jeffreys Deep is subparallel to this coastline. The north- 

 plateau of 4,000 feet in height (Arnheim Band and the 

 McDonnell Ranges). It must not be forgotten, moreover, 

 (see Fig. 1) that the Australian highlands make a remark- 

 able curve from the east to the north at the heads of the 

 Murray, and that Bass' Strait and the northern face of the 



.526-529. ■ Prin-ipK- t I , ;il.f..^.» i rrapi:v 



