AGASSIZ: LETTERS TO THE HON. GEORGE M. BOWERS. 79 



on tlie chart (H.O.2024). Ou leaving Manga Reva, we made three 

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

 the most one-third 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^ miles. A second 

 sounding of 24:5 fathoms off the eastern horn at less than one-half mile, 

 indicated on H.O. chart 2024 a distance of 2 miles from the horn ; and a 

 sounding of 241 fathoms one-fourth of a mile off the point which we had 

 visited (Vaiatekeue) indicated a distance of three-fourths 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.' Dutf, 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 3| miles from the breakers 

 in 1394 fathoms. 



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

 archipelago to the great atoll of Truk. If I remember 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 efi"ect 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 importance in the midst of the huge 

 lagoon which surrounds them. Tiie 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 Au Kena are 

 about 3, as are also the islets of the east face of the bai-rier 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 are seen 

 to the northeast about 4 miles off. When on the summit of the central 

 ridge of Manga Reva, one can, in a radius of a little more than 4 miles, 

 take in the whole panorama of Manga Reva, and get an impression of 

 the relations of its different parts far better than it can be conveyed by 



