TAHITI. 5 



any active igneous action, nor is there any well-defined crater to be 

 seen. Coral reefs, with occasional openings, are attached to the 

 shores, and the larger island (Tahiti) has also a sea reef, Between the 

 two reefs is an almost continuous channel for boat navigation, and on 

 the northern side they enclose many safe and commodious harbours 

 for shipping. On this side also vessels may pass from harbour 

 to harbour, within the outer reef. This reef varies in breadth from 

 a few yards to fifty, or even a hundred. The shore that adjoins 

 the coral reef is formed of black volcanic sand, occasionally mixed 

 with comminuted shells, which give it a grayish hue. Basaltic ridges 

 reach the sea at intervals, and form projecting points of moderate 

 elevation. 



We began without delay to overhaul the vessels, and the few sick 

 persons we had on board were sent on shore to a shed hired for the 

 purpose on Point Venus. 



An observatory was established at the same place, and furnished 

 with both astronomic and magnetic instruments ; and as soon as the 

 repairs of the vessels had made such progress as to permit it, parties 

 were formed for the survey of the four principal harbours and the 

 channels between them. These harbours, Matavai, Papaoa, Toanoa. 

 and Papieti, are so important to the many whale-ships which visit this 

 island, that I felt it an imperative duty to obtain accurate charts of 

 them all. At the same time, a large party of officers and naturalists 

 was ordered to cross the island, to reach, if possible, Orohena, one of 

 the highest peaks, and to visit Lake Waiherea. 



I had been in hopes of obtaining a full series of moon culminating 

 stars on Point Venus ; but I was disappointed, for it rained almost 

 every night. I was, therefore, compelled to rely for the longitude on 

 the chronometers alone, and restricted even in that method to observa- 

 tions of the sun. I was, however, well pleased to find that my results 

 differed from the best preceding authorities no more than 1' 33" of 

 space. These authorities give 149° 29' 43" W., for the longitude of 

 Point Venus. 



The mountains were obscured by clouds during the whole time of 

 my stay, and no angles could be taken for the measurement of their 

 heights, nor could the party I detached for the purpose reach their 

 summits ; but the Peacock remained for some days after my departure, 

 and Captain Hudson, with his officers, succeeded in measuring the 

 height of Aorai, the peak which is next in height to Orohena. This 

 he found to be six thousand nine hundred and seventy-nine feet ; and 

 as Orohena appeared to be about one thousand five hundred feet 

 higher, the height of the latter peak may be set down as about eight 



A2 



