384 PKOP. P. MAKSHALL ON THE [^Ug. I906, 



adjoining Peninsula, for the heights are greater and the valleys 

 more profound. Mount Cargill (2232 feet), Flagstaff (2204), Signal 

 Hill (1289), Swampy Hill (2195), Mihiwaka (1847), and Mopamii, 

 are the more prominent elevations. 



The more important streams are : the Kaikorai, flowing out to 

 the south of the district ; the Leith and North-East Valley streams, 

 flowing into the head of Otago Harbour ; the Waitati, flowing into 

 Blueskin Bay ; and the "Waikouaiti, in the extreme northern portion 

 of this district. 



Origin of the Land-Forms. 



The development of the physiographical features of the district 

 requires only a brief explanation. In recent volcanic areas, the 

 nature of the surface-features necessarily depends upon the varying 

 intensity of volcanic action throughout the district. In all ordinary 

 cases, the higher and more prominent elevations are the foci of 

 eruption. As time goes on, and some of these elevations are removed 

 by the ordinary processes of denudation, deep valleys may be 

 eroded and the whole topography of the district changed, until it 

 has the usual features found in all denuded land-areas. That this 

 § has occurred in the Dunedin area is evident at the first glance, for 

 almost everywhere are missed the conical hills and craters that 

 always distinguish the undestroyed volcanic districts. 



In nearly every instance the upper portions of the valleys are 

 steep and rocky, and the streams in them are small torrents. The 

 lower portions are open and flat, with bottoms formed of gravels 

 through which the streams meander. 



The streams enter the sea at the heads of far-reaching bays, or in 

 their lower course run over widespreading sand-flats. These bays 

 and depressions, now filled with sand, are evidently in their origin 

 valleys formed by the streams that now enter them, and, like the 

 lower portions of the present valleys, must have been excavated 

 when the land stood at a higher level relatively to the ocean than 

 it does now. 



This is most clearly seen in the case of Otago Harbour. It 

 is at once clear that this is no hollow formed by explosion, as in 

 Lyttelton Harbour and Akaroa Harbour in Banks Peninsula, but a 

 depression that has been eroded by running water. The opposing 

 peninsulas at Port Chalmers and Portobello, with the Quarantine 

 Islands between them, mark the old watershed, whence one stream 

 flowed north-eastward to Otago Heads, and the other south- 

 westward to St. Clair. Depression converted these stream-valleys 

 into sea-inlets, and its amount was sufficient to submerge the 

 watershed separating their head-waters. The continual northward- 

 setting drift and some movement of elevation finally blocked up 

 the south-western entrance to the inlet with sand, and since then 

 the outlet has remained constant at Otago Heads. 



Additional evidence in favour of this view is afforded by the 

 direction in which the bays opening into the harbour are directed. 



