136 Lecture on the Geology of [No. 9, new series. 



order that I may leave some time to devote to the volcanic forma- 

 tions which, from their great extent and the remarkable and beau- 

 tiful phenomena connected with them, render the Northern Island 

 of New Zealand, and especially the Province of Auckland, one of 

 the most interesting parts of the world. 



VOLCANIC FORMATIONS AND PHJENOMENA. 



Lofty trachytic peaks covered with perpetual snow, a vast num- 

 ber of smaller volcanic cones presenting all the varied characteris- 

 tics of volcanic systems, and a long line of boiling springs, fuma- 

 roles, and solfataras, present an almost unbounded field of interest 

 and, at the same time, a succession of magnificent scenery. 



It is only through a long series of volcanic eruptions, extending 

 over the tertiary and post tertiary periods, that the Northern Is- 

 land has attained its present form. It would be a difficult task to 

 point out the ancient form of the antipodean Archipelago, the site 

 of which is now occupied by the Islands of New Zealand. I must 

 confine myself to a simple indication of the events which have 

 given this country the form it was found to have by the South- 

 Sea Islanders on their arrival, many centuries ago, from the Sa~ 

 moan group, — a form in all main respects the same as is now be- 

 fore our eyes. 



The first volcanic eruptions were submarine^ consisting of vast 

 quantities of trachytic lava, breccia, tuff, obsidian, and pumice- 

 stone, which, flowing over the bottom of the sea, formed an 

 extensive submarine volcanic plateau. The volcanic action 

 continuing, the whole mass was upheaved above the level 

 of the sea, and new phaenomena were developed. The eruptions 

 going on in the air instead of under the sea, lofty cones of trachytic 

 and phonolithic lava, of ashes and cinders, were gradually formed. 

 These eruptions, breaking through the original submarine layers 

 of trachytic lava, breccia and tuff, raised them, and left them, as 

 we now find them, forming a more or less regular belt round the 

 central cones, and having a slight inclination from the centre out- 

 wards. These belts I shall have occasion to refer to under the same 

 of" tuff-craters" or cones of tuffs" or craters of elevation." In the 

 course of time the volcanic action decreased, and we must now 



