EXPLANATION OF THE MAPS. 
VOLCANIC FORMATION. 
1. The north side of the Manukau Harbour is formed of a rugged 
rocky coast wall composed of mighty layers of volcanic 
stone masses, consisting of angular fragments of the 
different volcanic basis of rocks—Trachy-Dolerite, Ande¬ 
site, &c., which are transformed landwards into different 
coloured conglomerate clays. 
2. On the southern side of the Manukau Harbour , and on both 
sides of the Waikato, thence to the Aotea Harbour, 
extensive strata of basaltic conglomerate cover the ter¬ 
tiary layers, and with these conglomerates are immediately 
connected masses of eruptive basalt, without forming 
distinct craters. 
3. The volcanic zone which encloses the Middle Waikato 
basin, and is situated between this and the Lake Taupo, is 
principally formed by trachyte and pumice, with which 
are connected a very long line of volcanos, such as Karioi, 
Pirongia, Kakepuku, Maungatautari, Aroha, and many 
others. These mountains consist of trachytic, andesitic, 
and doleritic rocks; their summits are decayed and 
destroyed, and their craters scarcely recognisable.. 
4. The volcanic formation of the Taupo zone consists of a 
rhyolithic and trachytic lava. The volcanic eruption 
which commenced in the tertiary period continued, and 
gave to the Northern Island its present form only in the 
quaternary period. The eruptive masses of the Taupo 
zone consist of lava (the richest known) of silicious earth, 
also of rhyolithic rocks of all kinds, with obsidian and 
pumice. Near the centre of the Northern Island, on 
the southern border of the great inland lake Taupo, the 
water of which fills a large sunken crater, there rises on 
a plateau of pumice of 2,000 feet above the level of 
the sea the two giant volcanoes of New Zealand, Tongariro 
and Ruapahu. The Tongariro volcano, which rises to an 
elevation of 6,500 feet, is yet active as a Solfatara, with 
two large and constantly steaming craters (Ngauruhoe 
and Ketetahi). Ruapahu, which is 9,000 feet high, is 
covered with everlasting snow, and its fires seem to be 
extinct. These two mountains are accompanied on their 
northern side by a number of smaller extinct volcanoes, 
