THE GEOLOGY OE NEW ZEALAND. 
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are well worth being noticed. The lava has, in many places, 
flowed under ground at such an inconsiderable depth as to 
bake all the superincumbent earth to the consistency of brick, 
which frequently contains beautiful impressions of the leaves 
of trees, which formerly grew on the surface. 
The next centre appears to be Waka-ari, White or Sulphur 
Island, which with its neighbour Moutohora, Whale Island, is 
still in action; the latter indeed is chiefly filled with solfatara and 
hot springs; but the former is a volcano rising out of the sea, 
from the crater of which a volume of smoke is always ascending, 
which is visible at a great distance. Large masses of sulphur 
are there produced, and the varied form and character of the 
molten rocks of this crater are very interesting. 
The grand centre of volcanic action extends from White 
Island to Rotorua, and thence by Taupo and Tongariro to 
Wanganui, a distance of nearly 200 miles, forming a continu¬ 
ous line across the entire width of the island. The number 
of boiling gulfs, solfatara, and boiling mud pools in that line 
is extraordinary. They are seen in every direction—in the 
forest, in the plain, and in the water. A large number of 
them are concentrated at a place called Tikitere, and a most 
extraordinary assemblage of them is found at Ohinemotu, which 
renders that place one of the most remarkable in New Zealand. 
At Paeroa, near the Waikato, there is one of the largest of 
these mud pools ; it is from sixty to a hundred feet wide ; in 
the centre, first an enormous bubble of mud arises, which 
gradually increases in height and size, and at last becomes a jet 
of mud eight or ten feet high, with several smaller ones on 
each side; the mud is thrown up in large masses on the sides, 
where it dries, and assumes a cubical form ; it readily separates 
into laminae of different thickness, which bear a very close 
resemblance to slate, and, perhaps, in this mud vortex is to be 
seen, on a small scale, what was once the state of a large por¬ 
tion of the earth’s crust, during the formation of slate. 
At Orakokorako, on the Waikato, the boiling springs are 
the pressure of the lava has caused the soil above to fall in, leaving wide 
apertures, by which the visitor now descends into them; the natives formerly 
used them as places of sepulture. 
