TAHITI AND EIMEO. 47 



This excursion furnished more full information in relation to the 

 geological structure of the island than had before been obtained. This 

 is exclusively volcanic, and the rocks are either compact, basalts, or 

 conglomerates of basalt and tufa, although no active volcano exists, 

 nor any well-defined crater, unless Lake Waiherea can be considered 

 as one. Through these rocks olivine and pyroxene are copiously 

 disseminated; cellular lava was found in some places, but neither 

 pummice nor obsidian ; quartz and mica were not observed, nor any 

 carbonate of lime, except in the form of coral rock. 



There is no conformity between the rocks of the centre of the island 

 and those which in most places extend inwards for a few miles from 

 the coast. The former are usually compact, of columnar structure, 

 and exhibit no appearance of horizontal stratification ; the latter lie in 

 horizontal layers, composed of scoriaceous and vesicular lava. In both 

 of these structures, singular twistings and contortions were observed. 

 Many dikes were seen to occur, not only in the mountains, but near 

 the sea-coast ; these were from three to six feet in width. 



All the rocks of the island appear to be undergoing rapid decompo- 

 sition. Even in places where the rock seemed to have retained its 

 original form of sharp edges and pointed pinnacles, it was found so 

 soft, to the depth of a foot or more, as to crumble in the hand. The 

 earth thus formed varies in colour from that of Indian red to a light 

 oehrey tint ; in consequence, many of the hills are of a red hue, and 

 one immediately behind Papieti, takes its name (Red Hill) from this 

 appearance. 



This decomposed earthy matter, mixed with the abundant decayed 

 vegetation of a tropical climate, forms, as may be readily imagined, a 

 soil of the greatest fertility, adapted to every kind of cultivation. On 

 the higher grounds, the soil thus constituted has the character of a 

 clay, and is in wet weather slippery and unctuous ; in lower positions 

 it is mixed with lime derived from coral and shells, which often tends 

 to augment its fertility. 



Iron abounds throughout ; on the mountains to such an extent that 

 compasses were found of little use from the local attraction by which 

 they were affected ; and on the shore, the sand was composed in part 

 of iron, which could be separated by the magnet. 



Water gushes out near the coast in copious springs, but none of them 

 were found hot, nor were any warm springs reported to exist. 



Papieti, in whose harbour we were now lying, is one of the largest 

 villages on the island ; being the ordinary residence of the queen, and 

 the abode of the foreign consuls. The foreign residents are also, for 

 the most part, collected here. Among all its dwellings, the royal 



