596 Transactions. 



The glacier that occupied the North-east Valley formed the fine amphi- 

 theatre-like cirque between Mount Cargill and Signal Hill, and, flowing 

 southward, joined the Dunedin glacier, truncating Logan's Point spur 

 into a broad platform as it turned around the lower slopes of Signal Hill. 



Dr. Marshall supplemented his remarks with respect to the supposed 

 inability of ice-thrust to bend or break the least resistant schist with some 

 observations apparently meant to convey the meaning that the ancient 

 ice in the Wakatipu region was incompetent to cause the bending of the 

 schists. In my Bulletin on that area, speaking of the outcrop-bending 

 the weak mica-schist of the Arrow and Shotover has suffered, I stated 

 (p. 43), " The bending of the rocks is the work of the ice-sheet that covered 

 the mountains in the glacial period. It often obscures the true dip." 

 Further on I mentioned that on account of this bending it was impos- 

 sible to get trustworthy observations for dip and strike over considerable 

 areas. 



Referring to the ability of ice to crumple and disrupt rocks, Geikie* 

 says, " While the general surface of the land has been abraded by the ice- 

 sheets, more yielding portions of the rocks have been broken off, bent back, 

 or corrugated by the pressure of the advancing ice." Further on he con- 

 tinues, " The laminae of shales or slates are observed to be pushed over or 

 crumpled in the direction of ice-movement." And, again, f speaking of the 

 bending of fissile strata, he says, " Similar effects, with even proofs of 

 contortion, may be observed under boulder-clay, or in other situations 

 where the rocks have been bent over and crushed by a mass of ice." 



In many places the freshness of the glaciated slopes and hummocky 

 moraines is as conspicuous on the coast-line as it is at Wakatipu, which 

 is the more remarkable when we observe that contiguous areas of hard 

 rock have been deeply dissected by streams. This differential erosion is 

 a common feature of glaciated regions, and has been a subject of much 

 discussion and speculation in Europe and America. Mr. G. W. Lamplugh, 

 F.R.S.jJ of the British Geological Survey, in a recent paper on the " Sur- 

 face Features of Glaciated Areas," when dealing with this matter, makes 

 the following interesting statement : "In the detailed examination of 

 districts overspread by glacial deposits, I have been constantly impressed 

 by the great discrepancy between the effects of erosion on contiguous 

 tracts. On the one hand, drumlins of boulder-clay, esker-ridges and kame- 

 mounds of sand and gravel, and moraines of incoherent rubble, though all 

 composed of material yielding readily to erosion, have retained with very 

 slight impairment their original shape and position in spite of the steepness 

 of their slopes, so that one might imagine that the forces of denudation 

 had been almost in abeyance in the district since the close of the glacial 

 times. On the other hand, a neighbouring stream-channel will often show 

 in the clearest manner that during the same period the erosive agencies 

 have been particularly energetic, so that the stream may not only have 

 cut its trench through a thickness of drift, but may also have notched 

 deeply into the underlying solid rock. My attention was particularly 

 directed to these divergent conditions in Ireland, where they are every- 

 where prevalent. But I have since recognised in varying degree the same 

 anomalies in every glaciated region that I have studied." 



* A. Geikie, " Geology," vol. ii, p. 1309. 



t A. Geikie, I.e., vol. i, p. ()69. 



% (i. W. Lamplugh, Geographical Journal, July, 1909, pp. 55-56 



