ROOM II. GEOLOGY OF NEW ZEALAND. 97 



the Northern Island, bear marks of wave-action to the height 

 of 100 feet above the present sea-level. In the interior of this 

 island there is a lofty central group of volcanic mountains, 

 some of the cones being still in activity ; the ancient lava- 

 streams appear to have been erupted from the base of the 

 craters. The highest mountains are Tongariro, which is esti- 

 mated at six thousand feet in height, and Mount Egmpnt, at 

 nine thousand feet : the summits are covered with perpetual 

 snow. There are many lakes which appear to occupy extinct 

 ancient craters. Earthquakes are not unfrequent, and of late 

 years some have occurred of unusual violence, from which the 

 town of Wellington suffered considerably. 



The comparatively modern terraces of loam and gravel which 

 stretch along the coasts at an elevation of from fifty to one 

 hundred feet above the sea, attest that great changes in the 

 relative level of land and water have taken place at no very 

 distant period. The existing rivers of New Zealand almost 

 everywhere cut deeply through accumulations of volcanic 

 detritus which in some places contain birds' bones ; and 

 these beds are here and there covered by marine and fresh- 

 water deposits of very modern origin. All these phenomena 

 indicate the oscillations to which the land has recently been 

 subjected. 



In the Middle Island, according to my son's observations, 

 as in the Northern, the lowermost visible rocks are clay-slate 

 and metamorphic schists, intersected by dykes of greenstone, 

 and compact and amygdaloidal basalt; and in some places 

 there are intruded masses of obsidian, and other volcanic 

 products. Hornblende and porphyritic rocks, gneiss and 

 serpentine occur ; but granite has not been observed. 



Mountain ranges of schistose and metamorphic rocks extend 

 through the country, from near Cloudy Bay on the north- 

 east, to the south-western extremity of the Island, a distance 

 of between three and four hundred miles ; their crests every- 

 where attain an elevation above the line of perpetual snow, 

 hence they were named the Southern Alps by Captain Cook. 

 These hills are flanked by volcanic grits, and covered at their 

 base by alluvial deposits, that have evidently originated from 

 the decomposition of trachytic rocks and earthy lavas. 



No active volcanoes are known in the Middle Island, nor 

 have any extinct craters been discovered : but as the physical 



