CussEN. — Thermal Activity in Piuapehu, Crater. 379 



of the lava flows, are immense beds of consolidated tuff ; on the 

 lower slopes the soil of volcanic loam is forming. 



The waters of Wangaehu have a sulphurous taste and smell. 

 Its course can be traced down the eastern side of the mountain 

 from nearly the top of the cone in which is the hot lake ; it may 

 therefore be inferred that the water receives its character from 

 this lake, through a subterranean passage in the mountain. 

 Since discovering that the crater contained hot water, I have 

 mentioned the fact to the oldest Natives in the district, and they 

 all concur m the belief that it is something new. I am, however, 

 inclined to doubt this, and to believe that a low volcanic heat 

 must have prevailed there throughout. Five years ago, when 

 engaged in triangulation on the Kaimanawa Eanges, I noticed 

 hanging over Kuapehu, in the position of the crater, what seemed 

 to be a cloud mass. This I remarked more than once, but I did 

 not know of the existence of the lake at that time, and I con- 

 sidered that it must be a cloud or fog rising through some of the 

 gorges of the mountain, although it closely resembled a column 

 of steam. I may also mention that some eighteen years ago, (1 

 am informed,) an abnormal flood occurred in the Wangaehu 

 Eiver, carrying down with it large blocks of snow and ice. 

 There had been no heavy rains at the time to account for this 

 flood : it is therefore reasonable to infer that it was caused by 

 an escape of the warm water from the lake, passing down 

 through some underground passage below the edge of the water, 

 and thawing the snow and ice on the mountain side. This, 

 however, appears certain, that before or about the beginning of 

 April, a considerable increase of volcanic heat in the Euapehu 

 crater took place, which continued to increase until towards the 

 end of May, after which time I had no opportunity to observe it. 



On the 16th of April I noticed a well-defined column of 

 steam rising fi-om the crater, several hundred feet above the 

 mountain top ; it was also visible several days subsequently. I 

 showed it to several of the Natives, who said they never had 

 known of such a thing before. If it were of common recurrence, 

 and in such volume, I think it impossible that it could have 

 escaped the notice of the Natives. 



On the 23rd May, the weather being very clear and bright, a 

 larger column than usual ascended fi-om the crater, about 300 

 feet above the mountain, spreading out horizontally into a 

 cloud-like mass, the outside portions of which descended again 

 and rolled down the mountain side. Towards noon this column 

 began gradually to decrease, until it disappeared altogether by 

 sunset. Since the end of May the dull weather prevented any 

 further observations of the mountain. Should the volcanic 

 heat so increase as to cause a sudden thaw of the ice and snow 

 which fill up the crateral hollows of the mountain and mantle 

 its sides for several thousand feet, the result must be heavy 



