338 Transactions. 



must be accepted that there is no positive evidence in regard to this. No 

 appeal can be made to the blotting effect of weathering if the statement 

 is true that " a striking feature of this great glaciation is the remarkable 

 freshness of the ice-grooved surfaces." 



In the coastal ranges near the Nuggets the development of the many 

 subsequent or strike stream- valleys, eroded to a great depth in hard rocks, 

 is an undoubted proof that those hills have been submitted to uninterrupted 

 stream erosion for a great lapse of time. I have failed to see any effect of 

 glacial erosion in the coastal hills near Dunedin, Timaru, Oamaru, Taieri 

 Mouth, or between the Nuggets and Waikawa, or in the Hokonui Hills. 



Mr. Hardcastle has cited the north-west face of Moimt Horrible, near 

 Timaru, as an example of glacial erosion. The form of this slope and that 

 of the valley of which it forms one of the sides are, however, quite different 

 from those found in glacial areas, and appear to me to be those of a typical 

 valley and escarpment formed by stream erosion. The typical glacial topo- 

 graphy is unknown in the coastal regions, and has not been described in two 

 Geological Survey Bulletins dealing with Central Otago.* 



(Jr.) Glacial pavements : There have been no descriptions of ice-striated 

 surfaces of rock or of boulders. Hutton mentions some that had been 

 stated to be ice-worn. He was, however, able to convince contemporary 

 opinion that the grooves were not due to ice, but to unequal weathering 

 of the rock. Actual experiments with artificially polished rock-surfaces of 

 the same kind of rock as that which he mentions have convinced me that 

 these irregular, curved, and branching grooves are produced by chemical 

 reagents, which decompose certain of the rock-constituents. 



(5.) Erratic boulders : No foreign boulders have yet been discovered on 

 the Dunedin hills or elsewhere on the coast. It is absolutely impossible 

 that bouldeis of schist should be entirely absent if the country had been 

 covered by an ice-sheet that radiated from Wakatipu or from some other 

 point on the main divide, for the whole country is formed of schist to within 

 a very few miles of Dunedin. The importance of this is realised when the 

 results of the late Antarctic expeditions are recalled. In South Victoria 

 Land the coastal country round the bases of the great volcanic cones and 

 well up on their flanks is strewn with granite blocks and other rocks brought 

 apparently from great distances. At the Gaussberg, where the ice com- 

 pletely covers the mainland, so that all the coast and even the mountain- 

 tops are invisible, it is still found that the Gaussberg itself is strewn with 

 boulders of much variety brought from the hidden continent. Similar 

 results were obtained in Graham Land by Arctowski. The Swedish ex- 

 pedition in Louis Philippe Land also found numbers of erratic blocks in that 

 ice-bound area. 



Much emphasis has lately been laid upon the thickness of the ice in the 

 Lake Wakatipu basin, f and upon its effect in removing and transporting 

 material. In general it is well to acknowledge the great extent to which these 

 descriptions have added to our knowledge of the dettiils of glaciation of the 

 district. There are a few matters to which exception may be taken. It is 

 perhaps iinfortunate that the Arrow basin should be called a " cirque," for 



* Smce the above was wi-itten, Saddle Hill, Mount Watkins, and other points have 

 been called roches moutonnees. The absence of polished and grooved rock-surfaces, 

 and the large number of loose boulders on the summits, ai)pear sxifficient to disprove 

 this. These hills are volcanic |)lugs. 



t Bulletin No- 7, N.Z. Geological Survey (New Series), ]). 3(i. 



