1 66 CORALS AND CORAL ISLANDS. 



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

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

 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. 146. 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 conglomerate. Beach, regular as usual, six to ten feet 

 high, consisting of coral sand, and fragments of worn shells, 

 with occasional exuvioe of crabs, remains of Echini, fish, &c. The 

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



Aratica or Carlshoff^ 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 north-west 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 

 larger, 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. 



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, according to estimate from ship- 

 board, 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 v/hole. 



