382 PROF. P. MARSHALL ON THE [Aug. I906,. 



In the present paper an attempt will be made to deal more fully 

 with this Otago district, although it must at once be stated that the 

 result should be regarded only as a breaking of the ground of an 

 area that will afford abundance of inspiring work for several gene- 

 rations of geologists, who will here find material in plenty and in 

 astonishing variety for testing theories in regard to magmatic 

 differentiation or other agencies controlling the nature of volcanic 

 emissions. 



Position and Surface-Features. 



The Otago Peninsula forms a prominent projection from the 

 southern portion of the eastern coast of the South Island of New 

 Zealand, in latitude 45° 52' S. and longitude 170° 31' 30" E. It 

 extends for 14 miles from north-east to south-west, but is nowhere 

 more than 6 miles wide. It is united to the mainland at its south- 

 western extremity by a narrow strip of sand, about a mile long and 

 a mile wide, of recent accumulation. Its coast-line is irregular, 

 and where fronting the Pacific Ocean the land rises at most of 

 the headlands abruptly, often vertically, to a height of 300 or 

 400 feet. The greatest height of cliff is found at Highcliff, the top 

 of which is 800 feet above sea-level. The indentations in this 

 coast-line are fringed by a beach of white quartz-sand, which is 

 constantly travelling northward under the influence of the heavy 

 northward-setting seas and current. Two inlets are of especial 

 size — Hooper's Inlet and Papanui Inlet, each 2 miles long by 1 wide. 

 They are extremely shallow over nearly all of their extent, and 

 flat muddy bottoms are exposed at low tide. The entrances are 

 almost closed by large flat expanses of sand, rising here and there 

 into dunes. The sand-flat is in each case on the north side of the 

 inlet, and a narrow channel extends between it and the rocky cliffs 

 that form the south side of the entrance. 



Similar sand-flats, with their surface ranging to 20 feet above 

 high-water level, are found in all the sheltered bays. In most 

 cases, they completely fill the bay right up to its rock-walls, but 

 occasionally, as at Tomahawk, a lagoon is formed whence the- 

 rainfall escapes over a depression in the sand-barrier ; and through 

 this the sea-waves may wash into the lagoon during periods of 

 high tides or heavy weather. 



The coast-line of the peninsula that forms the south-eastern 

 border of Otago Harbour has sloping sides ending in short cliffs. 

 Pour miles from the north-eastern point — Taiaroa Head — a sandy 

 beach extends north-eastward for 3 miles ; and the sand from a 

 portion of this — the Pauone beach — has been blown by the south- 

 westerly winds right over the peninsula, here half-a-mile wide and 

 400 feet high, into a bay on the opposite sea-coast. The whole 

 of this inner coast-line has numerous small bays and headlands ; 

 all of the bays are shallow, and much mud L flat is exposed at low 

 tide. One peninsula— at Portobello — projects outward for a full 

 mile at: right angles to the coast. 



