122 BULLETIN OF THE 



upon an examination of these charts, much less to attempt any but very 

 indefinite deductions for local phenomena or conditions. 



It seems scarcely necessary to discuss the opinions of Wilkes, 1 who 

 dismisses the whole basis of the theory of coral reefs, besides the special 

 theory of Darwin, and who calmly says : " After much inquiry and due 

 examination, I was unable to believe that these great formations are 

 or can possibly be the work of zoophytes ; . . . I cannot but view the 

 labors of these animals as wholly inadequate to produce the effects 

 which I observed." There seems to be only one critical observation 

 worthy of remark. When speaking of the formation of lagoons he sug- 

 gests the possibility of the washing influx and efflux of the sea to carry 

 off in the shape of mud or sand, or in solution, the strata underlying the 

 central part of a lagoon. Wilkes further says : " It seems almost 

 absurd to suppose that these immense reefs should have been raised by 

 the exertions of a minute animal, and positively so to explain the pecu- 

 liar mode of construction by which reefs of an annular shape are formed, 

 when in nine cases out of ten they are of other figures." The last part 

 of his statement seems to have been lost sight of in the discussions on 

 atolls. 



In striking contrast to Wilkes's opinions are the observations of 

 Couthouy, one of the naturalists of the United States Exploring Expe- 

 dition, who published in 1842 his views on the Coral Islands of the 

 Pacific. 2 He suggests that corals are limited in their range of growth 

 by temperature rather than depth, and that wherever this is not be- 

 low 76° Fahrenheit, then, ceteris paribus, they will be found to flourish. 

 Couthouy admits the correctness of the theory advanced by Darwin, 

 and believes the great thickness of the reefs to have been produced by a 

 gradual and long continued subsidence of the original shelf of coral, while 

 the surface was maintained at the same level as at first by the unceas- 

 ing additions made by the polyps. He also believes that the whole of 

 Polynesia is at present slowly rising, and gives his reasons for believ- 

 ing in a former subsidence of a great continent, mainly based upon the 

 identity of the volcanic and coralline rocks composing the majority of the 

 islands of Polynesia. Couthouy describes the seaward side of the encir- 

 cling reef of the Paumotu group as representing a succession of terraces 

 or plateaus ; the lowest of variable breadth, seldom exceeding one huu- 



1 Wilkes, Charles, Narrative of the United States Exploring Expedition, Lon- 

 don, 1845, Vol. IV. p. 268. 



2 Joseph P. Couthouy, " On Coral Formations in the Pacific," Journ. Bost. Soc. 

 Nat. Hist., 1842, p. 66. 



