Extinct Volcanic Craters. 179 



ately, these sketches almost entirely omitted any notice of 

 the description of land surveyed, and, in fact, comprised merely 

 the outline of the coast and the net- work of the rivers, so 

 that it became necessary to examine for myself the physical 

 features of the country. 



^' On a closer examination, the variety of geological forma- 

 tion proved to be much greater than I had at all anticipated. 

 What chiefly took up my time was the investigation of the 

 remarkable extinct volcanic caves of the Isthmus of Auckland, 

 which, so far as regards the great number comprised within a 

 small space, and the peculiarities of their cave and crater 

 configuration as modifying the lava streams, must be pro- 

 nounced unique of their kind. Within a circuit of only ten 

 miles from Auckland I had to mark down 61 different 

 points of eruption ! An excursion southwards to Manukau 

 Harbour, and the mouth of the Waikato westward, led to our 

 finding important petrifactions at the south source of the 

 Waikato, and along the west coast to the discovery of belem- 

 nites and fossil ferns in excellent preservation. Thus for the 

 first time the secondary strata of New Zealand were bared to 

 view. Fm'ther excursions to the Drury and Papakina districts, 

 as also to the Walroa River, were rewarded by the confirma- 

 tion of the extension thither of the brown-coal formation, after 

 which I extended my investigation northwards to the Waita- 

 keri, and the peninsula of Wangaparoa. 



'' My map, so far as completed, and sent to the Colonial 

 Government for their use and to be copied, embraced by the 



N 2 



