xvi TAWAKI 229 



in a straight line for a distance of between 13 and 14 miles, its 

 breadth varying between ij and 2 J miles. Its greatest elevation 

 of nearly 1,600 feet is attained at its western end ; and it diminishes 

 irregularly in height as one proceeds towards Undu Point, where 

 a height of 400 feet is maintained about a mile from the cape. 

 It is bordered by reefs sometimes a mile in breadth, and the reefs 

 prolong the promontory for another three miles beyond Undu 

 Point. As indicated by the 100-fathom line, the submarine 

 contour corresponds to that of the land, and the extent of marine 

 erosion during the existing relations of land and sea is evidently 

 displayed in the breadth of the reefs. I found no sign of upraised 

 reefs ; and although diligent inquiries were made nothing could be 

 learned of any hot springs. 



It will be seen from the following remarks that pumice-tuffs, 

 quartz-porphyries, and oligoclase-trachytes, are the prevailing 

 rocks. On the north side they may be regarded as continuous 

 with the acid rocks of the region extending from near Lambasa 

 to Thawaro Bay. On the south side they commence in the 

 vicinity of Tawaki. 



(1) The District Extending two and a half miles 



West of Tawaki 



When proceeding eastward along the north coast of Natewa 

 Bay one enters the region of acid rocks between 2 and 2\ miles 

 west of Tawaki. Here the country is much broken, picturesque 

 hills with bare precipitous faces rising up near the coast, one of 

 which named Natoto has a rudely conical and truncated form. 

 Grey oligoclase-trachytes having a specific gravity of 24 and 

 possessing the characters described on page 308, prevail in the 

 district extending west of Tawaki. Sometimes they occur in 

 mass ; but they often form agglomerates. A singular pitchstone- 

 agglomerate occurs at the coast at the foot of Natoto. The 

 pitchstone, which has a specific gravity of 2*48, is a semi-vitreous 

 form of a hypersthene-augite andesite. It shows abundant small 

 pyroxene prisms in its glassy groundmass and is referred to the 

 prismatic sub-order (5) described on page 289. 



(2) Naithombothombo Range 



A high range of hills, forming the backbone of this part of 

 the island, extends eastward for about five miles from Thawaro 

 and Tawaki. It is named " Naithombothombo " in the Admiralty 



