STRUCTURE OF CORAL ISLANDS. 203 



Mania' i, Wilson's or Waterlandt, Paumotu Archipelago, 

 14° 25' S., 146° W. 15 miles by G, trending E. N. E. A 

 large lagoon with a deep entrance on the west side. Shape 

 obi on 2: triangular. 



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. 179. 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. The reef-rock is either a compact 

 limestone, showing no traces of its composite origin, or a con- 

 glomerate. Beach, regular as usual, six to ten feet high, con- 

 sisting of coral sand, and fragments of worn shells, with occa- 

 sional exuviae of crabs, remains of Echini, fish, etc. The en- 

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



Aratica or Carlslioff, Paumotu Archipelago, 15° 30' S., 

 145° 3CK W. IT 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, one to thirty cubic feet and larg- 

 er, tumbled together as on the preceding. Some blocks of 

 coral on the shore platform very large ; one eight feet high 

 and fifteen in diameter, containing at least 1,000 cubic feet. 



JSfairsa 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, according to estimate from ship- 



