168 DISTRIBUTION OF CORAL-REEFS. Ch. VI. 



where a slight tremor is only rarely felt, the shoalness of 

 the lagoon^channels round some of the islands, the 

 number of islets formed on the reefs of others, and the 

 broad belt of low land at the foot of the mountains, all 

 indicate that these islands have not undergone for a long 

 period, any movement of subsidence, although their 

 encircling reefs must on our theory have been originally 

 produced through subsidence. 1 



Although Dana admits that atolls and barrier-reefs 

 must have been originally formed by the subsidence of 

 their foundations, he believes that a large number of 

 atolls, situated between the Paumotu or Low group to the 

 east and the Feejees to the west, and northward nearly 

 as far as the equator, have recently been uplifted to the 

 height of a very few feet. 2 Mr. Couthouy came to a 

 similar conclusion during the same expedition with 

 respect to many of the Paumotu atolls. These observers 

 ground their belief chiefly from having found the great 

 shells of the Tridacna vertically embedded in coral-rock, 

 at a height at which they cannot now exist. Mr. 

 Couthouy also states that he found corals standing on 

 the shores and in the midst of the lagoons, from 12 to 

 30 inches above the sea-level, with the tips of their 

 branches dead. He also refers to masses of coral-rock 



1 Mr. Couthouy states (Kemarks, p. 44), that at Tahiti and Eimeo 

 the space between the reef and the shore has been nearly filled up by 

 the extension of coral-reefs of the kind which within most barrier-reefs 

 merely fringe the land. From this circumstance, he arrives at the same 

 conclusion as I have done, namely, that the Society Islands have 

 remained stationary during a long period. 



2 Corals and Coral Islands, 1872, pp. 199, 345. See also Mr. Cou- 

 thouy's Eemarks on Coral Formations. 



