jlpril — sept. 1859.] the Province of Auckland. 147 



ka-rewarewa are the most interesting. Waikite, the principal " nga- 

 wha," issues from the top of a siliceous cone some 20 feet high, 

 and is surrounded by several smaller geysers, boiling mud-pools, 

 and solfataras. At intervals of considerable length, sometimes 

 extending to many months, all these ' ngaivhas 1 begin to play toge- 

 ther and form a scene which must be most wonderful and beautiful. 



The hot springs of Ohinemutu form agreeable bathing -places, 

 the fame of which is already established. 



10. The last in the line are the great solfataras on the pumice- 

 stone plateau between Rotorua and Rotoiti — such as Tikitere and 

 Ruahine. 



I will now say a few words in explanation of these phenomena. 



All the waters of the Springs are derived from atmospheric 

 moisture, which, falling on the high volcanic plateau, permeates 

 the surface and sinks into fissures. Taupo — the axis of which 

 corresponds with the line of the Hot Springs — may also be consi- 

 dered as a vast reservoir, from which the lower springs are sup- 

 plied. The water, sinking into the fissures, becomes heated by 

 the still-existing volcanic fires. High-pressure steam is thus ge- 

 nerated, which, together with the volcanic gases, decompose the 

 trachytic rocks. The soluble substances are thus removed by the 

 water, which is forced up, by the expansive force of the steam and 

 by hydrostatic pressure, in the shape of boiling springs. The in- 

 soluble substances form a residuum of white or red fumarole clay, 

 of which the hills at Terapa round Rotomahana and the Pairoa 

 consist. 



All the New Zealand hot springs, like those of Iceland, abound 

 in Silica, and are to be divided into two distinct classes — the one 

 alkaline, and the other acid. To the latter belong the solfataras 

 characterised by deposits of sulphur, and never forming intermit- 

 tent fountains. All the intermittent springs belong to the alka- 

 line class, in which are also included the most of the ordinary 

 boiling springs. Sulphurets of Sodium and Potassium, and Car- 

 bonates of Potash and Soda, are the solvents of the Silica, which, 

 on the cooling and evaporation of the water, is deposited in such 

 quantities as to form a striking characteristic in the appearance of 

 these springs. 



