On the Volcanic Country of Auckland, New Zealand

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Abstract
B y the map of New Zealand it will be seen that in the 36th degree of south latitude the Northern Island of New Zealand is so much narrowed as to form an isthmus of about six miles in width from east to west, connecting the broader and higher land on either side. This isthmus, like the land immediately to the north and south of it, has an undulating surface, rising in some places to hills of about 600 or 7OO feet above the sea. The cliffs which bound its eastern side show beds of soft sandstone, indurated clay, and mud-rock, with layers of volcanic ashes, and, occasionally, seams of lignite and coal. The whole seems to belong to the Tertiary formation, and probably to the Eocene period. Organic remains are rarely met with. But at one locality, between Kohuroa and Omaha, Terebratulœ . (of which specimens are forwarded to the Society) occur at the junction of the volcanic ashes and clay-beds above-mentioned. The higher land to the south of the isthmus—beginning on the eastern coast—consists of, first, clay-slate, then rocks of the Cretaceous formations, and lastly, a magnetic sandstone-rock, mixed with a black conglomerate. This series rises into hills of 800 of 1000 feet above the sea. To the northward of the isthmus the Tertiary is bounded on the eastern slope by a black trap-rock of a very close texture, next by a black boulder-rock, and finally, on the west coast, by a trachytic breccia, rising into peaks and ridges of

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