518 NOTES ON THE RECENT ERUPTIONS IN THE TAUPO ZONE, N.Z., 



rhyolite are hurled high into the air and relieved from even 

 ordinary atmospheric pressure, forms a froth which is so im- 

 mediately cooled and solidified as to retain its spongy character 

 for ever. Of these materials the whole surface of the Taupo 

 Zone is composed. No wonder then if heated alkaline waters 

 percolating through very hot and soluble rocks of this kind in the 

 Rotomahana country should become heavily impregnated with 

 silica, to be deposited as their temperature falls, and upon exposure 

 to the air, in those beautiful Sinter Terraces which have made the 

 name of an otherwise insignificant little lake famous throughout 

 the world. (1) 



If we follow the Waikato from its sources on the N.E. flanks 

 of Ruapehu and Tongariro, we shall see that it leaves upon the 

 left the dormant volcanoes of the Kuharua District, rising from 

 their more ancient base of trachytic lava, and still maintaining in 

 their innumerable hot springs very sufficient evidence that their 

 energies are not even now quite worn out. Thence it flows into 

 the now tranquil basin of Lake Taupo, sunk as it were into the 

 tertiary pumice beds, but revealing in its shores the almost 

 unbroken rim of rhyolitic lava which underlies them. 



From this lake the river itself and its tributaries, beset with 

 boiling springs and geysers, leaves the Lake District on the right, 

 and turning sharply to the north-west, cuts its way through the 

 plateau to the broad expanse of the Middle Waikato. 



It is remarkable that the very margins of the Lake District 

 drain outwards to the Waikato, and not inwards to the lakes, 

 though these lie at a lower level. And this seems to indicate 

 that the water supplies for the hot springs of Rotomahana and its 

 neighbourhood must travel by subterranean channels, and in an 

 opposite direction to the surface drainage, in their course to 

 ultimate emergence. 



(1) Dr. Hector has observed that the Sinter of the Lake District, 

 deposited by heated landwaters, is represented in White Island, where sea- 

 water alone has been concerned in the decomposition of the mother rock, by 

 Sulphate of Lime. 



