218 CAPT. F. W. HTJTTOlf ON THE 



In the neiglibourliood of Auckland many scoria-cones with well- 

 preserved craters occur at very slight elevations above the sea. 

 These are younger than the clays belonging to the Wanganiii System 

 round Manukau Harbour, and have never undergone marine denu- 

 dation ; but some of the tuff- craters, such as Lake Pupuki on the 

 north shore, are of submarine origin. 



Obsidian occurs in many places and is particularly plentiful on 

 Mayor Island in the Baj^ of Plenty. Perlite is found in the Hot- 

 springs district ; and a finely laminated rhyolite, called lithoidite 

 by Eichthofen, is found at Totara on the east shore of Lake Taupo *. 

 Tachylyte occurs but rarely. We have no glassy basaltic lava- 

 streams, as in the Sandwich Islands and Priendly Islands. Leucite 

 has been found in a basalt of uncertain age near Castle Point on the 

 east coast of "Wellington t. Anorthite occurs in the volcanic rocks 

 of Campbell Island J, but the age of these also is unknown. The 

 only active volcano in 'New Zealand is Tongariro, and its eruptions 

 are feeble. White Island, in the Bay of Plenty, appears to be in 

 tlie solfatara stage. It has never been known in eruption, and 

 there is no appearance of recent lava-streams §. 



Two interesting sections of volcanoes occur in the sea-cliffs of the 

 IN'orth Island. I described the one on the west coast, between 

 Port Waikato and Eaglan, some years ago ||. The other, which is 

 situated at the west head of Tamaki Eiver, near Auckland, I have 

 the late Mr. Heaphy's authority for saying is the same as the one 

 figured by him %, and copied into the works of Scrope and Judd**. 

 This is the only crater near Auckland that is cut completely 

 through by a sea cliff ; and I quite agree with Dr. Hochstetter that 

 it is a tuff-crater only, without any lava-stream tt- 



Distribution of Volcanic RocJcs in the North Island. 



I have already pointed out that, judging from the relative position 

 of the Maitai and Hokaniii Systems, it is probable that the ge-anti- 

 clinal of* New Zealand passes through the centre of the jSTorth 

 Island from Wanganui to the Bay of Plenty. If now we draw a 

 line parallel to this axis from Mt. Egmont, through the Karioi at 

 Eaglan, and on to Mercury Bay in the Coromandel peninsula, we 

 find that to the north-west of this line the intermediate rocks have 

 been followed by basic rocks (none of which are known south-east 

 of the line) without any acidic rocks. On the ge-anticlinal itself, 

 from Euapehu to the Bay of Plenty, the intermediate rocks are 

 followed by acidic rocks without any traces of basic rocks. To 

 the east of the axis basic rocks occur again on the east coast of 



* Hochstetter, 'Reise der Novara,' Greol. i, p. 113. 

 t Colonial-Museum Laboratory Reports, x. p. 48. 

 + EilhoL Comptes Rendus, Feb. 1882. 



§ Edwin, Trans. N. Z. Inst. i. p. 57 (new ed. p. 463) ; Hector, Trans. I^. Z. 

 Inst. iii. p. 278. 



|] Quart. Journ. Greol. Sec. xsv. p. 13. 



% Quart. Jom-n. Geol. Soc. xvi. p. 242. ** Volcanoes, p. 165, f. 66. 



ft 'Reise der No vara,' Geology, i. p. 176, no. 28, and Map. 



