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exhibited by the New Zealand hot springs are throughout similar 
to those of the hot springs upon Iceland. The interesting results, 
to which the investigations of Krug von Nidda, Sartorius von 
Waltersliausen , von Bunsen and others have led upon Iceland, 
may therefore be mostly applied also to New Zealand. As to 
the mechanical processes , the intermittent springs, or those which 
at certain periods display an increased state of ebullition , — raised 
sometimes to regular, geyser-like water eruptions, — may be dist- 
inguished from the permanent springs, the surface of which is in 
a state of constant repose, or in a uniform state of ebullition. The 
former may, as I have explained in the beginning of this chapter, 
be designated as Puias, the latter as Ngawlias. With this distinc- 
tion corresponds moreover the chemical difference of alkaline and 
acid springs. 
Both kinds of springs owe their origin to the water, permeat- 
ing the surface and sinking through fissures info the bowels of the 
earth , where it becomes heated by the still existing volcanic fires. 
High-pressure steam is thus generated, which accompanied by vol- 
canic gases, such as muriatic acid, sulphurous acid, sulphuretted 
hydrogen and carbonic acid, rises again towards the colder surface 
and is there condensed into hot water. The overheated steam 
however, and the gases decompose the rock beneath, dissolve cer- 
tain ingredients, and deposit them again on the surface. According 
to Bunsen’s ingenious observations, a chronological succession takes 
place in the cooperation of the gases. The sulphurous acid acts 
first. It must be generated there, where rising sulphur- vapour comes 
into contact with glowing masses of rock. Wherever vapours of 
sulphurous acid arc constantly formed, there acid springs or sol- 
fataras arise. Incrustations of alum are very common in such 
places, arising from the action of sulphuric acid on the alumina 
and alkali of the lavas; another produce of the decomposition of 
the lavas is gypsum (or sulphate of lime), the residuum being a 
more or less ferruginous fumarole - clay , the material of the mud- 
pools. To the sulphurous acid comes sulphuretted hydrogen pro- 
duced by the action of steam upon sulphides , and by the mutual 
