nto lakes, as in the case of those of the Eifel;
but generally they are dry or have a floor of morass. Of the
crater-lakes, those of Kohuora, five in number, are perhaps the most
remarkable; and in the case of two of these the central cones of slag
appear as islets rising from the surface of the waters. The fresh-water
lake Pupuka has a depth of twenty-eight fathoms. To the north of
Auckland Harbour rises out of the waters of the Hauraki Gulf the cone of
Rangitoto, 920 feet high, the flanks formed of rugged streams of basalt,
and the summit crowned by a circular crater of slag and ash, out of the
centre of which rises a second cone with the vent of eruption. This is
the largest and newest of the Auckland volcanoes, and appears to have
been built up by successive outpourings of basaltic lava from the
central orifice, after the general elevation of the island.

[Illustration: Fig. 26.--Forms of volcanic tuff cones, with their
cross-sections, in the Province of Auckland.--No. 1. Simple tuff cone
with central crater; No. 2. Outer tuff cone with interior cinder cone
and crater; No. 3. The same with lava-stream issuing from the interior
cone.--(After Hochstetter.)]

Before leaving the description of the tuff-cones, which are a peculiar
feature in the volcanic phenomena of New Zealand, and are of many forms
and varieties, we must refer to that of Mount Wellington (Maunga Rei).
This is a compound volcano, in which the oldest and smallest of the
group is a tuff-crater-cone, exhibiting very beautifully the outward
slope of its beds. Within this crater arise two cones of cinders, each
with small craters. It would appear that after a long interval the
larger of the two principal cones, formed of cinders and known as Mount
Wellington, burst forth from the southern margin of the older tuff-cone,
and, being built up to a height of 850 feet, gradually overspread the
sides of its older neighbour. Mount Wellington itself has three craters,
and from these large streams of basaltic lava have issued forth in a
westerly direction, while a branch entered and partially filled the old
tuff-crater to the northwards.

Southwards from Manukau Harbour, and extending a short distance from
the coast-line to Taranaki Point, there occurs a plateau of
basalt-conglomerate (_Basaltkonglomerat_), with sheets of basaltic lava
overspreading the Tertiary strata. These plateau-basalts are intersected
by eruptive masses in the form of dykes, but still there a