Thomson. — Glacial Action in Otago. 327 



snows of the mountains in this district show their influence in the last month 

 of the year, by melting and flooding the torrents, so may the mountain glaciers be 

 said to have a marked epoch, special to themselves, at the end of the glacial age, 

 which epoch is recorded by the moraines now extending round or at their ancient 

 lower termini. Speaking fi-om recollection, and going back seventeen years, 

 I was struck with the immense hillocks of confused rubble, earth, and boulders 

 extending round the southei-n shores of Ohau to Pukaki, and rising near 

 300 feet in elevation. There was, now, no apparent cause for this until we 

 turned our eyes to view the receding glaciers, to be descried in the distance, 

 high up in the mountains. So, at the southern end of Lake Wakatipu, 

 similar phenomena are to be observed, leading to the same conclusions. The 

 Francis Joseph Glacier, on the West Coast, extends down to 700 feet from the 

 sea level, and those on the eastern slopes of the Southern Alps to 2,774 feet. 

 Thus, in a particular valley on the West Coast, the glacial age may be said to 

 be only 700 feet perpendicularly distant j while, horizontall}', it is, as stated 

 before, 23 degrees of latitude southward. On comparing the measurements, it 

 will be at once noted that those of the valleys of the Waitaki and the Clutha 

 are much modified ; this is owing to the Pukaki and Wanaka Lakes forming 

 portions of the valleys of the Waitaki and Molyneux. The cause of this 

 exception has been ascribed, by one class of observers, to the scooping efiects 

 of mountain glaciers, while, by another class, it has been ascribed to the 

 original depressions when the mountains and valleys assumed the geological 

 arrangement now existing. As much has been advanced on both sides of the 

 question, I will content myself by suggesting that we will not be doing much 

 violence to either theory by giving both of them weight in modelling the surface 

 of our valleys to their present form. Thus, I may ask those gentlemen who 

 adhere to this lake-scooping action alone, why the Ahuriri had not a lake as 

 well as its neighbour the Ohauj the Shotover and Arrow as well as the 

 Dart and Pees ; and the Oreti as well as its neighbour the Mararora ; all 

 flowing out of glacial mountains and under similar conditions % May we not 

 give weight to the axiom, that where there are high elevations, so must there 

 be low depressions ; and where one varies in height, so will the other in depth ? 

 Thus, may not the valley of the Wanaka have been originally lower than that 

 of the Matukituki, as their respective passes are lower ; and so, while the 

 valley of one is filled with water, the other is filled with the bed rock, overlain 

 with sand and shingle. 



Then, to revert to the influence that glaciers of probably 3,000 and more 

 feet in thickness would have in scooping action, or modification of shores and 

 bottom, we must consider the nature of the rocks acted on. 



The resisting power of the hard schists, being as hard as granite, that line 

 the Wakatipu Lake, varies from 5,5001bs. to ll,000tt)s. per square inch. Now, 



