92 president's address — section c. 



ment of volcanic mountains. If, for example, the level of the 

 North Island of New Zealand were lowered by 7,000 feet, Ruapehu, 

 Ngauruhoe and Egmont alone would extend above the surface of 

 the ocean. The line connecting their summits is almost at right 

 angles to the true structural axis of the island. 



Using the arrangement of the island groups as a basis, Dana, 

 Gregory and Suess have all made statements as to the direction 

 of structural lines in the Pacific. The opinions of these authors 

 need brief recapitulation. Thus Dana makes the following state- 

 ments : — 1 See Map Plate. 



1. Over the Pacific area there are no prominent north-south 

 courses in its ranges. 



2. Ranges in the Pacific Ocean trend not far from N.W. by W. 

 One transverse range crosses the middle South Pacific — the New 

 Zealand — commencing in New Zealand and islands south of it with 

 the course N.35° E. continuing through the islands and the Tonga 

 group, the latter trending N. 22° E., and this is the nearest north- 

 south line in the ocean except towards its western border. 



3. Oceanic ranges are seldom straight, but, instead, change 

 gradually in trend through a large curve or a series of curves. 



4. There are parallelisms between the trend of the New 

 Zealand range and that of the east coast of North America, and also 

 between the trend of the foot of the New Zealand boot, with the 

 Louisiade group and New Guinea group further west. 



Later Dana defined four mountain chains in the Pacific.^ 

 Three of these belong to the north-westerly system and one to the 

 north-easterly system. 



1. Hawaiian chain, Hawaii to Kauai to 175° E. A total length 

 of 1,500 miles. 



2. Polynesian chain sweeps through the centre of the ocean 

 with a length of 5,500 miles It consists of a series of parallel 

 ranges, with a mean trend north west by north. Paumotu, Tahiti, 

 Rurutu and Hervey (Cook) Islands are parallel fines in the east of 

 the chain. Samoa, Gilbert, Radack, and Rafick to Wake's Island 

 are others in the western parts. 



3. Australasian chain (a) New Hebrides, Solomon, New 

 Ireland and Admiralty Island, 2.000 miles ; (b) North of New 

 Guinea, Louisiade, New Caledonia, and the foot of the New Zealand 

 boot. 



4. New Zealand chain, Macquarie to Vavau Island, 2,500 miles- 

 This transverse chain is at right angles to the Polynesian system, 

 where they meet. It is nearly central to the ocean. The New 

 Zealand chain has great significance. 



J. W. Gregory'^ has described the groups of Islands as arranged 

 in festoons, and of these he distinguishes five. 



1 Uana, E. S. : "Characteristics of Volcanoes," 1890, p. 361. 



2 Dana, E. S. :" Manual of Geology," 4th edition, 1895, p. 37. 



3 J. W. Gregory : "Geography, Structural, Physical, and Comparative," 1908, p. 275. 



