282 



hydrochloric acid present in the water of the lake, of which it is the most 

 charactei'istic constituent, would indicate that the decomposition of sea water 

 is one result of the chemical action that is in progress. 



These characters, and the absence of silica from the incrustations, obviously 

 distinguish the thermal waters of White Island from the Puias and Ngawhas 

 of the Rotorua and Taiipo Districts, where the chief agent in prodvicing 

 chemical change must be rain and lake waters, which hold a comparatively 

 small amount of mineral matter in solution. It therefore forms one of a 

 third class of hot springs in New Zealand, in addition to the alkaline and acid 

 springs which are so well described in Professor Hochstetter's admirable work 

 on New Zealand {Chap. 18). 



Samples were obtained of the water of the lake, and of the semi-fluid 

 mud from the fumaroles, which have been analyzed for me by Mr. Skey, 

 and the results compared with the composition of similar samples previously 

 forwarded. 



The water taken from the lake at a part clear from any incrustation, after 

 standing for some time, deposited a slight sediment consisting wholly of gypsum 

 in minute crystals. The transparent water then had a specific gravity of 

 1 "088, and possessed the following composition : — 



COMPOSITION OF ONE GALLON, IN GRAINS. 



Hydrochloric acid . . , . . . 



11,642-4 



Sulphuric acid ..... 



1,405-6 



Sulphurous acid ..... 



traces. 



Alumina . ..... 



627-2 



Protoxide of iron, with a little sesquioxide 



546-0 



Soda ....... 



313-6 



Potash ....... 



162-4 



Lime ...,.,. 



106-4 



Magnesia ...... 



022-4 



Silica and siliceous matter 



023-8 



"Water .,,.,.. 



. 61,366-2 



76,216-0 

 Also contains traces of phosphoric acid and ammonia. 



This proximate composition of the water may therefore be rendered 



centesimally as follows : — 



Su-lphate of iron . . , . . , 1-514 



Sulphate of soda ...... -941 



Sulphate of potash ...... -394 



Sulphate of lime . . . . . . -337 



Sulphate of magnesia . . . . . -087 



Sulphate of alumina . . . . . -115 



Sesquichloride of aluminum , . . . 2-433 



Siliceous matters . . . , . . "031 



Hydrochloric acid, y?'ee . . . . . 13-631 



Water 80-517 



100 



