276 Transactions. 



been washed away by the heavy rains which fail upon that side, and which 

 must have fallen for a verv long time to have produced so great an effect " 

 (5, p. 161). • 



In recent years Marshall (7, p. 98 ; but see also 11, p. 445), Park (12, 

 p. 16), and others appear to have accepted Hochstetter's explanation of 

 the structure of the Southern Alps without question. In 1908, however, 

 the writer pointed out that a series of ancient rocks designated by him the 

 Greenland series* occurs along the western margin of the Southern Alps. 

 These rocks, if Hochstetter's hypothesis were correct, should show the same 

 folding as the rocks of the Arahura series, which form almost the whole of 

 the Southern Alps ; but, instead of that being the case, it is found that they 

 are folded almost at right angles to the trend of the Alps (10, pp. 31, 36, 97). 

 This fact is completely opposed to the idea that the present alpine chain is 

 " only the eastern half of a huge geanticlinal " of which the western wing 

 has disappeared. 



The great difference in lithological character between the schists east 

 of the granitic mountains that have been supposed to represent the core 

 of the alpine anticlinal and the much less metamorphic argillites and grey- 

 wackes of the Greenland series in a corresponding position on the western 

 side of the granitic mountains is in itself strong evidence against what may 

 be called the Hochstetterian view. 



Von Haast was undoubtedly to some extent aware of the structure of 

 the Greenland rocks, and it was probably in order to avoid the difficulty 

 of reconciling this with the structure of the Arahura series, as well as to 

 obviate the difficulty caused by the difference in lithological character, that 

 he supposed his Westland formation to be (in part at least) younger than 

 the alpine folding (2, p. 244). There appears, however, to be no field evi- 

 dence of any kind in favour of this view. 



What, then, is the general structure of the Southern Alps ? As has 

 been elsewhere pointed out by the writer (10, p. 43), an exposition of the 

 principles underlying the answer to this question may be found in Eduard 

 Suess's great work, " The Face of the Earth," where it is maintained that 

 folded momitain-chains of the alpine type are due to overthrusts along lines 

 where more yielding strata are pushed against buttresses of immovable 

 rocks. In the case of the Southern Alps, Suess's main criteria are satisfied. 

 There is a gentle rise from one side — the east — and a steep descent on the 

 other. The strata on the western side are overturned schists. Along the 

 western margin are great faults, believed to be of the overthrust type (10, 

 pp. 43, 71). These faults are associated with a line of granitic mountains,! 

 which correspond to Suess's cicatrices that mark a wound in the earth's 

 crust. To the west of these, beyond the main overthrust, comes a buttress 

 of Greenland sedimentaries, folded in most places almost at right angles 

 to the alpine strike. 



Some imperfections in the field evidence that occur to the writer may 

 here be mentioned. North of the Waitaha River granite is well developed 

 along the base of the Alps, but for a hundred miles or more southward no 

 granite except a small outcrop in Mount Bonar (10, p. 132) has been observed. 

 Again, the Greenland buttress is apparently by no means continuous along 

 the western base of the Alps. It is, however, well developed from Bell 



* Equivalent to part of Von Haast's Westland series (2, p. 250), and to Bell and 

 Fraser's Kanieri series (8, p. 19). 



t In places gneiss partly covers the granite. 



