536 



Proceedings. 



Mr. McKay pointed out that the evidence derived from the thickness of the silt 

 deposit at the mouth of the Pahau Eiver, instanced by the author, was only proof of the 

 extent to which it had been dammed back by the flood in the Hizrunui, and that the flood 

 was not due to landslips amongst the mountains in which the larger rivers take their rise, 

 as streams such as the Pahau, which rise much nearer to the east coast, were relatively as 

 much flooded as the Hurunui and the Waiau-ua. He was of the opinion that the new 

 shingle-fans formed by some of the creeks in the Waiau-ua Gorge were not necessarily 

 evidence that the flood was of a wholly unprecedented character, and endeavoured to show 

 how circumstances irrespective of the mere amount of rainfall might have brought about 

 the results mentioned by Mr. Travers. Viewed as a geological fact, he thought it likely 

 that greater floods had occurred within the recent period, or since the gravel terraces were 

 formed within the Waiau-ua Gorge. 



The President, before calling on Mr. Travers to reply, remarked that he thought the 

 paper was one of great importance to those in charge of public works that were proposed, 

 especially in this particular district. He had since last meeting looked up the meteoro- 

 logical records for the period when this flood took place. These early records were not so 

 complete as those now made, but he had obtained sufiicient proof of the passage over the 

 middle part of New Zealand of a great atmospheric depression, from the 2nd to 4th Feb- 

 ruary, 1868, and that the centre passed N.E. of that part of the islands which suffered 

 most, which fully accounted for the unusual direction of the wet wind, which on this oc- 

 casion came from the eastward. The depression revolved round a low pressure of 28-6, and 

 by means of the accompanying diagram of the isobaric lines he showed reasons for believing 



30-6 



,-30- 





lel.ShSGS. 



that it reached New Zealand from the tropical parts of the Pacific Ocean lying to the N.E. 

 of New Zealand, instead of having had the more common course from the westward. At 

 the period referred to an extensive anticyclonic area prevailed over Australia, producing 

 a diiierence of pressure of no less than two inches between there and New Zealand. The 

 cyclonic disturbance that produced the floods was revolving along the eastern edge of this 

 area of high pressure as it did not affect Australia. The translation of a mass of warm 

 and moisture-laden tropical air to higher latitudes, and its impingement on the eastern 

 flanks of the New Zealand mountains, sufficiently accounts for the extraordinary character 

 of this flood. 



