124 The Taraivera Outbreak 



in the billy bubbled, it never became heated nearly np to the 

 ordinary boiling point, and the men, struck with the strange- 

 ness of the phenomenon, concluded that it was an "uncanny" 

 omen, and so abruptly abandoned their task. 



If this story has a substratum of truth — as it well may 

 have — it would indicate an excessive barometrical fall over 

 Wairoa during the eruption. Such a fall might have been 

 due to the enormous volume of superheated steam and gas 

 which was projected into the atmosphere, and which, accu- 

 mulating round and banking up over the vent, as a dome- 

 shaped cloud, would give to the several planes of pressure 

 enveloping it, a sharp, short, qua-qua-versal dip, down 

 which the cold and dense, and therefore heavier strata of 

 superincumbent air, would quickly slide away to every point 

 of the compass, piling up at the bottom of the slope, as an 

 atmospheric talus, and so forming a peripheral ring of higher 

 pressure round the volcano, but at a little distance from it. 

 The displacement of such a volume of heavy air by an equal 

 volume of attenuated air would register itself at the earth's 

 surface below it in a fall of mercury, and it would lower 

 the boiling point of water for every altitude within the same 

 area. Thus it would render the newspaper story quite 

 possible. 



Again, it is well to remember that the abrupt creation of 

 such a disposition of the atmosphere would account for the 

 tornado blast which played such havoc near the volcanoes 

 during the second phase of the eruption. For, over the 

 fissure, the ascending vapours must have operated as an 

 atmospheric chimney, and this would create a powerful 

 indraught of low-level air, and the enclosing ring of high- 

 pressure — that is, the atmospheric talus before suggested — 

 would, if it existed, increase the indraught. 



It would be very interesting to learn all the wind 

 movements which occurred that morning round the vol- 

 canoes. 



The ofiicial reports give the changes at Wairoa and 

 Rotorua only; but these two places are situated in the 

 same quadrant of a cyclone centred over Tarawera, and the 

 absence of settlement in the surrounding region will render 

 it almost impossible to get the information desired. 



Still, we ought to get some information as to the direction 

 taken by the great tornado from the bearings of the fallen 

 trees, and some more general information from the distribu- 

 tion of the ejecta. 



