42 ON CORAL REEFS AND ISLANDS. 



Manhii, Wilson's or Waterlandt, Paumotu Archipelago, 14° 

 25' S., 146° W. 15 miles by 6, trending E.N.E. A large la- 

 goon with a deep entrance on the west side. Shape oblong tri- 

 angular. 



Shore platform as usual ; mostly under water at low tide. 

 Large masses of coral here and there, standing on this reef, either 

 cemented to it or loose. One top-shaped mass is figured on p. 29. 

 High water did not reach the part of it which was most worn ; 

 and this was evidently owing to the fact that the action of the 

 swell, or waves, is greatest above the actual level of the tide at 

 the time. This mass was not of fragmentary composition ; it 

 was apparently the remains of a single individual Pontes. Another 

 loose mass was five and a half feet high, and averaged ten feet 

 across, (fig. 3, p. 30.) It consisted of large masses of Astraeas, 

 Madrepores, and Porites cemented together, and contained im- 

 bedded shells, an Astraea, Cyprasa, &c. The reef-rock is either 

 a compact limestone showing no traces of its composite origin, 

 or a conglomerate. Beach, regular as usual, 6 to 10 feet high, 

 consisting of coral sand, and fragments of worn shells, with oc- 

 casional exuviae of crabs, remains of Echini, fish, &c. The en- 

 trance to the lagoon is deep and narrow, with vertical sides. 



Aratica or Carlshqff. Paumotu Archipelago, 15° 30' S., 145° 

 30' W. 17 miles by 10, trending N. E. Large lagoon, with a 

 good entrance for vessels. The reef fronting south, bare for 

 nine miles : on northwest side, mostly very low, with only here 

 and there a clump of trees ; occasionally a line of wooded land 

 for a quarter of a mile on the east side ; more continuously 

 wooded on the north. The bare parts, mostly covered with 

 blocks of coral, 1 to 30 cubic feet, and larger, tumbled together, 

 as on the preceding. Some blocks of coral on the shore plat- 

 form very large ; one 8 feet high and 15 in diameter, containing 

 at least 1000 cubic feet ; it lay on the reef and was not connected 

 with it ; below it, the platform was 6 inches higher than the sur- 

 face either side, owing to the action of the sea. These blocks 

 are in all instances rough angular, and appear as if they had been 

 thrown up by the sea, and left exposed to wear from the rains 

 and spray. 



Nairsa or Dean's, Paumotu Archipelago, 15° S., 148° W. 

 44 miles by 17, trending W. N. W. Northern shore mostly 

 wooded ; southern with only an occasional islet, connected by 

 long lines of bare reef. In these intervals, the reef stood eight 

 feet or so out of water, and was worn into a range of columns, 

 or excavated with caverns, so as to look very much broken, 

 though quite regularly even in the level of the top line. 



We might continue these descriptions ; but the above, with 

 the details before given, will convey a general idea of the whole. 



