Agassiz — Albatross Expedition to the Eastern Pacific. 371 



Manga Reva, in contrast with those along the west face of the 

 lagoon flats to the west of the eastern barrier reef. 



There is a northeast horn of the eastern barrier reef in the 

 extension of Manga Reva Island, forming the northern culmi- 

 nation of the central bight of the eastern face of the barrier 

 reef. From that point the reef flat runs westerly to form the 

 northern horn about 3 miles north of Manga Reva Island. 

 The position of the outer reef cannot be correct on the chart 

 (H. O. JN r o. 2024). On leaving Manga Reva we made three 

 soundings close off the reef flat line of breakers — one off Tekava, 

 at the most -J of a mile from the reef, in 225 fathoms. Our 

 position, plotted by tangents to the volcanic islands or by their 

 summits, indicated in this case, on the chart, a distance of 1-J 

 miles. A second sounding of 245 fathoms off the eastern horn 

 at less than \ mile, indicated on chart No. 2024 a distance of 

 2 miles from the horn ; and a sounding of 241 fathoms \ of a 

 mile off the point which we had visited (Vaiatekeue) indicated 

 a distance of f of a mile on the chart. 



The slope of the Gambier Archipelago to the east is steep. 

 On coming in sight of Manga Reva we sounded in 2070 fathoms 

 at a distance of 11 miles from Mt. Duff, that is, 6 miles from 

 the outer edge of the reef bearing southwest ; and on coming 

 out we sounded again half-way to that point at a distance of 

 3J miles from the breakers in 1394 fathoms. 



One cannot fail to be struck with the similarity of the Manga 

 Reva Archipelago with the great atoll of Truk. If I remem- 

 ber rightly, Darwin also called attention to this from a study 

 of the charts. Yet, owing to the great size of Truk, no less 

 than 125 miles in circumference, and the great distance of the 

 barrier reef from the encircled volcanic islands, the effect as 

 one steams into Manga Reva is totally different from that 

 produced by Truk. In the latter some of the islands, though 

 large, and of the same height as those of Manga Reva, are 

 much more scattered, and seem of comparatively small impor- 

 tance in the midst of the huge lagoon which surrounds them. 

 The barrier reef islets of Truk are from 11 to 15 miles distant 

 from the encircled volcanic islands. In Manga Reva, which is 

 only 45 miles in circumference, after passing the small islands 

 in the southern and open part of the lagoon when once off 

 Maka-pu, we can fairly well take in the atoll as a whole. The 

 western island (Tara Vai) is only 5 miles off ; Manga Reva 

 and An Kena are about 3, as are also the islets of the east face 

 of the barrier reef ; these distances, as you approach the 

 entrance to Rikitea, are constantly growing less, so that when 

 in the gap between Manga Reva Island and Au Kena, at the 

 foot of Mt. Duff, none of the larger islands are more than 3 

 miles off ; and the islets of the eastern face of the barrier reef 



