420 Trcuisactions. — Botany. 



miles distant from the mainland of New Zealand, the sea be- 

 tween is comparatively shallow, the average depth, according 

 to the Admiralty charts, being from 40 to 50 fathoms ; but 

 immediately on the outside of the group, the depth rapidly 

 increases, and soundings of nearly 200 fathoms have been ob- 

 tained within six or seven miles, while in a due north direction 

 the 500-fathom line is not more than twenty miles distant. 

 It is obvious that the islands stand on the very edge of a sub- 

 marine plateau, which stretches from forty to fdiy miles 

 northward of New Zealand, and then suddenly sinks into 

 nuich deeper water. It is natural to assume that they have 

 been at one time connected with the mainland, and, in support 

 of this, it may be observed that their geological structure 

 corresponds very closely with that of the greater portion of the 

 North Cape peninsula, the rocks composing both being slates 

 of probably Palaeozoic age. The late Dr. Hochstetter ex- 

 pressed the opinion that " the peculiar features of the northern 

 peninsula of the North Island are only to be accounted for by 

 adopting the theory of a gradual sinking of the land," and 

 other geologists maintain similar views. It must also be 

 remembered that the hypothesis which, so far, has given the 

 best explanation of the origin and peculiarities of the fauna 

 and flora of New Zealand has for its chief factor a former ex- 

 tension of New Zealand to the north-west. 



It is an interesting question as to whether subsidence is 

 still taking place in this part of New Zealand ; for it would 

 require little more to convert the North Cape peninsula into 

 a group of scattered islands. North of Ahipara, the whole of 

 the west coast to within a few miles of Cape Maria van 

 Diemen is composed of low sand-hills, often not more than 

 50ft. above the level of the sea. On the eastern side the coast 

 is also chiefly composed of sand, with the exception of the 

 hills at Cape Karakara, to the north of Doubtless Bay, and 

 the narrow strip near Ohora Harbour on which Mount Camel 

 stands. The North Cape peninsula proper is moderately high, 

 the hills near the North Cape and near Cape Maria van Diemen 

 being nearly 1,000ft. above sea-level ; but even there a 

 stretcli of sandy and swampy land joins Tom Bov^line's Bay 

 with the east coast, lying so low that a fall of 50ft. would 

 submerge it, and convert the North Cape into an island. In 

 a similar vray, one or two of the arms of Parengarenga Har- 

 bour approach very closely to the west coast. A subsidence 

 of 150ft. would unite Doubtless Bay with Eangaounu Harbour 

 and the opposite coast, would join both Ohora and Parenga- 

 renga Harbours with the west coast, would cut off the North 

 Cape from the rest of the peninsula, and would convert that 

 portion of the province north of Mongonui into a chain of 

 widely-separated islands. The Three Kings Islands, however, 



