Vol. 70.] LAYAS AT THE NORTH HEAD, OTAGO HARBOUR. 



383 



were the products of the activity of a single volcano. Some diffi- 

 culty was experienced in coming to a conclusion on this point, 

 since all the outward signs of volcanic action have now heen 

 destroyed by subaerial erosion, and therefore the surface-features 

 that exist do not indicate the point from which the lavas were 

 emitted. 



Internal evidence also was sought in the dip of the various flows 



Fie. 1. 



of lava and in the extent to which they suffered from erosion 

 during the intervals between the different periods of activity. The 

 dip or slope of the lavas was found to be remarkably uniform. 

 The amount of dip is 14-6°, and is directed 20° south of east. The 

 rise is thus 1 in 4, a little to the north of west. This rise is in 

 the direction of the high country (1600 feet) near Mihiwaka and 

 Mopanui; but it is considerably steeper than the actual average 

 rise of the countrv in the same direction. 



2d2 



