PENRHYN ISLAND. 269 



the effects which I observed, and I was satisfied that the very appear- 

 ance of the reefs was sufficient to contradict any such impression. 

 The ingenious theory of Darwin, which has of late been promulgated. 

 and which holds that an equal subsidence and growth are taking plac 

 is alike at variance with the configuration, extent, and general con- 

 struction of the reefs. 



Jn all the reefs and islands of coral that I have examined, there are 

 unequivocal signs that they are undergoing dissolution. Thus, it will 

 be recollected, that in the first volume of this narrative, I gave various 

 sketches of coral blocks now existing on the top of reefs, and also 

 spoke of the various shelves, soundings, and longitudinal cracks that I 

 had observed. All these phenomena have been since those first obser- 

 vations repeatedly met with. To account for the position of these 

 blocks, it has been assumed that they had been thrown up by the sea ; 

 but their positions, weight, and situation, are such as to contradict 

 such an idea. They are found in many cases standing erect on their 

 smaller ends, and have evidently formed an upper shelf, of which they 

 are now the sole remains. In every observed instance, they were at 

 some distance from the outer edge of the reef on which they stand, 

 and they were also seen covered with debris of the coral, that has 

 been mentioned as forming the highest portion of the islands. It 

 would be utterly impossible for any sea to toss so great a weight to 

 such a distance ; and if such masses were even broken off from a reef 

 by the action of water, they would undoubtedly have obeyed the laws 

 of gravity, and descended to the unfathomable depths beneath them. 



The low coral islands, as far as they have been investigated, both 

 by boring and sounding, have shown a foundation of sand, or what 

 becomes so on being broken up. 



The elevated coral islands which we have examined, exhibit a 

 formation of conglomerate, composed of compact coral and dead 

 shells, interspersed with various kinds of corals, which have evidently 

 been deposited after life has become extinct. A particular instance of 

 this was seen at the island of Metia, and the same formation was also 

 observed at Oahu. 



The abrading effects of the sea on all the islands and reefs, was 

 evident, for they exhibited throughout a worn surface. Some living 

 corals are indeed found at the surface, but a few inches beneath it the 

 reef is invariably a collection of loose materials, and shows no regular 

 coralline structure, as would have been the case if it had been the 

 work of the lithophyte. 



All the coral islands lie within an ocean subject to the effects of 

 volcanic action, and we have no reason to doubt that they would be 



X2 



