114: president's address — SECTION c. 



effects of aridity are in evidence, though this climatic condition 

 has been of comparatively short duration. A noteworthy feature 

 in the arid areas of mica-schist, is the occurrence of numerous tors, 

 sometimes as much as 80 feet high, bounded by joint-surfaces, and 

 resulting apparently from the removal of the surrounding 

 material, which was more disintegrated by some peculiarity of 

 differential weathering, and thus the tor-pattern has been etched 

 out. (Cotton, 1917.) A further instance may be seen in the wide 

 stretohes of sand-dunes in the rift-valley of the Clutha at Cirom- 

 well, which have resulted from the destruction by rabbits and by 

 fire of the protecting vegetation on the high terraces of the river, 

 or by removal of the sand from the river-bed itself. (Cockayne, 

 1911.) 



Even more striking is the effect of glaciation, concerning which 

 much has been written in previous decades, though but little in 

 the last one, the literature of which is immediately under review. 

 The views of Hutton (1900) and Marshall (1912) that the glacia- 

 tion was restricted to the highlands, and was rather of the nature 

 of separate glaciers, than a continuous ice-sheet, represents the 

 opinion of the majority of New Zealand geologists, though it must 

 be noted that locally, as about Lake Te Anau, the valley-glacier 

 appears to have deployed into a sheet of considerable area, filling 

 a tectonic basin. Indeed, the effects of glaciation may be more 

 restricted than even Marshall at first assumed (1912). It is at 

 least doubtful whether we may properly class as of morainic 

 origin certain great terraces at Clyde and Alexandria, and the so- 

 called " Taieri moraine," near Dunedin, has been described as of 

 fluviatile origin. (Trechmann 1918, Marshall 1918.) It is more 

 clear than before' that thei great glaciated lake-basins,* river- 

 valleys, and fiords had a pre-glacial origin, either tectonic or by 

 erosion, in areas weakened by the presence of 'extensive shatter- 

 belts ; though their form has since been profoundly modified by 

 the glaciation. Interesting examples of the combined effects of 

 structural and glacial influences in determining valley forms have 

 been described by Kitscn and Thiele (1910) in the Waitaki Valley, 

 the southern boundary of Canterbury; and by Speight (1918) in 

 the Hurunui Valley, the northern boundary. In Milford Sound 

 the preliminary observations of Cotton and the writer, indicated 

 that it may be possible subsequently to recognise several distinct 

 stages in the glaciation of that district. 



While several of the fc'atures of the North Island have be'cn 

 claimed tci be of glacial origin, tliis conclusioin appears in most 

 cases to' be open to doubt, but it may be we'll for the present to 

 refrain from accepting the general statemeait that there is no sign 

 of glaeiation in the North Island, until these and other certain 

 features (e.f/., those described by Adkin, 1912) have been more 

 fully investigated. It should be noted, however, that Moore 



* This has been pointed out by Park (1910, p. 230) in the case of Lalse Walvitipu. 



