I 4 JT. VOLCANIC PHENOMENA IN NEW ZEALAND. 99 



country for several miles, is studded with lakes and pools, 

 and fountains of hot and boiling water ; and groups of mud 

 ponds, or stufas, occur in considerable numbers. Some of 

 the boiling torrents of the mountain find their way to 

 the delta of the river TTaikato, and cover a space of 

 two miles square with an assemblage of thermal springs. 

 The surface of this area appears to be only a thin crust 

 of pumice and a friable sulphureous earth, with chalce- 

 donic and siliceous incrustations, spread over volcanic 

 caverns. 



The most stupendous of these boiling pools is partly 

 surrounded by a cliff sixty feet high, which is oxidized, 

 corroded, and undermined from the effects of the heated 

 vapours, which are continually issuing forth in jets. At 

 the base of this cliff the pond is constantly boiling with a 

 white foam, and throwing up fountains eight or ten feet 

 high, with great noise and violence. Silex is thrown down 

 by the boiling waters in the state of stalagmitic concretions, 

 and this deposit resembles in colour and solidity the flint 

 of the English chalk. This generally insoluble mineral is 

 here held in solution by the alkaline elements and very high 

 temperature of the water. 



" Another and still more striking example of a thermal 

 lake," observes Dr. Dieffenbach, from whose interesting 

 work on New Zealand the preceding notice is taken, "is 

 that of Rotu-Mahanu. Imagine a deep lake of a blue colour 

 surrounded by verdant hills, and in this lake several islets, 

 some showing the bare rocks, while others are covered 

 with shrubs : while on all of them steam issues from a 

 hundred openings between the green foliage without im- 

 pairing its freshness. On the opposite side is a flight of 

 broad steps of the colour and aspect of white marble with 

 a rosy tint from siliceous incrustations, over which flow T ed 

 a cascade of boiling water into the lake. A part of this 

 lake is separated from the rest by a ledge of rocks forming 

 h 2 * 



