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THE GEOLOGY OE AUCKLAND. 
♦ 
observation of the Natives, who have thus indicated the true line 
of the chief volcanic action in this island. 
Having now described the older and more extensive volcanic 
phenomena of the interior , I proceed to notice the later pheno¬ 
mena of volcanic action in the immediate neighbourhood of Auck¬ 
land. 
THE AUCKLAND VOLCANIC DISTRICT. 
The isthmus of Auckland is completely perforated by volcanic 
action, and presents a large number of true volcanic hills, which, 
although extinct and of small size, are perfect models of volcanic 
moun tains. These hills—once the funnels out of which torrents of 
burning lava were vomited forth, and afterwards the strongholds of 
savage cannibals—are now the ornaments of a happy land, the 
home of peaceful settlers, whose fruitful gardens and smiling 
fields derive their fertility from the substances long ago thrown 
up from the fiery bowels of the earth. 
My Geological Map of the Auckland District contains no 
less than sixty points of volcanic eruption within a radius of 
ten miles —the variety of which, together with the regularity of 
their formations, gives very great interest to this neighbourhood. 
The newer volcanic hills around Auckland are distinguished 
from the older ones in the interior, not only by their age, but 
by the different character of their lava—the older being tracingtic, 
while the Auckland are all basaltic. 1 have not yet mentioned 
the difference between Trachyte and Basalt. I will therefore 
say a few words in explanation. The difference consists in the 
minerals of which the rocks are composed. Trachyte is com¬ 
posed of a mixture of glassy feldspar (, Sanidin ) and hornblende : 
obsidian and pumice-stone are the usual concomitants of 
trachytic lava. Basalt consists of a minutely-crystalline mass 
of feldspar mixed with augit ; an admixture of greenish grains 
of Olivin is characteristic of basalt. 
In order to gain a clear idea of the history of the Auckland 
volcanoes, we must suppose that before the period in which the 
Auckland isthmus was slowly raised above the level of the 
sea, a submarine volcanic action was already going on. The 
products of this submarine action are regular beds of volcanic 
ashes, which form highly interesting circular basins with strata 
always inclining from within, outwards. Ton will at once 
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