1859.] HEAPHY VOLCANIC COUNTRY, NEW ZEALAND. 247 



and especially No. 42, on the map, PI. XII., are instances of this. 

 In the latter the eruption has taken place between two streams, and 

 the lava has flowed to the confine of each, and there cooled. 



In many cases the actual points of eruption must be hidden by 

 the matter that has flowed out, while the contiguity of the edges 

 of lava-streams flowing from other craters has destroyed the insu- 

 larity of the emitted mass. The most interesting, however, of these 

 phenomena are where, after a period of eruption, a partial collapse 

 has taken place, and the crater (if it may be so called) has subsided 

 within itself : I think the point No. 20 on PI. XII. may be considered 

 as of this kind. 



The 3rd subclass of the fourth series is the elevated conical hill 

 with its crater. I will describe three kinds, each of which may be 

 considered as a type of several others that occur in the district. 



a. Mount Albert (No. 16 on PI. XII.) is a mound, about 350 feet above 

 the sea, the base of the cone being about one-third of a mile in dia- 

 meter. The crater is about 80 or 100 feet deep, and the lip on the 

 S. W. side is broken away. A lava-stream has flowed out on this side, 

 and continued its course along one of the natural valleys, over the 

 Tertiary clays, to the sea at Auckland Harbour, a mile and a half to 

 the N.AV. The lava-stream has not expanded much laterally, perhaps 

 on account of a stream and a swamp that touched its sides ; but it 

 has kept on its way, rolling, as it were, within partially cooled sides, 

 until it reached the sea, where its course is for the present lost. 



A question perhaps arises, as to whether this lava-stream flowed 

 out of the crater through the present gap, which its weight caused 

 to give way ; or whether the cone resulted from an eruption of ashes 

 subsequent to the welling-out of the lava-stream. In some instances 

 (Mount Smart, No. 22 on the map, PI. XII.) the lava-stream leaves 

 the mountain at a point opposite to the crater-gap, as if the piling- 

 up of the cone were subsequent to the basaltic eruption. There is 

 but one section of a crater yet discovered (No. 45 on PL XII.) 

 whore the effect of the tide has broken away one side of the cone : 

 and the section here has since been made more perfect by quarry- 

 ing operations. See fig. 5. 



In this case, I think it is evident tbat the basaltic lava rose up to 

 b, where it flowed over the sides ; but those sides, especially at c, 

 wen- so steep as to cause a severance of the stream, and the lava 

 rolled down at once to tL It may be a question whether the bed a 

 was subsequently added, or the basalt, b, found its way through, at 

 intervals, without disturbing a. The greal compactness of texture of 



the surface of ft leads, perhaps, to a belief in the latter alternative. 



ft. There are near Auckland about tour instances of cones with 

 lateral craters. 



The larger mound in fig. 6 shows a well-formed, bul broken-down 

 crater; a subordinate mound also shows q crater; a third shows no 

 cup, but a lava-stream flows from the base of it ; and a fourth and 

 fifth show protuberances without apparent craters. 



Are Nos. ;*, A, & ") in this diagram (fig. 6) bills once containing 

 craters that have been filled up by the subsequent raining-in of ashes 



