170 
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 re- 
spect 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 
Cordier, in his Report on the Voyage of the Astrolabe (vol. i. p. cxi.), 
speaking of Vanikoro, says the shores are surrounded by reefs of 
madrepore, ‘ qu'on assure etre de formation tout-a-fait uioderne.' 
1 Mr. Couthouy states (Remarks, 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. 
Couthouy’s Remarks on Coral Formations. [See Wilkes’ Exploring 
Expedition, vol. i. chap, xv.] 
