102 J. D. Dana — Geological History of Oahu. 



found for the coral rock, and more than 1,000 for broken 

 corals ; and over 700 is reported by Mr. McCandless from a 

 well in the Eua district, about five miles west of Honolulu. 

 The facts lead to the inference that the subsidence amounted 

 to at least 800 feet, and that it corresponds to the coral-reef 

 subsidence which Darwin's theory requires. Mr. McCandless 

 informed me that fragments of corals like those of the modern 

 reefs were brought up from the various levels. 



This evidence of subsidence to the amount stated is not, how- 

 ever, complete. Doubt remains because the corals brought up 

 in fragments have not been examined by any one competent to 

 decide on their actual identity with existing species ; I could 

 not find that any of them had been preserved. The import- 

 ance of their preservation and careful study is now understood, 

 and we may hope before long to have the doubt removed. As 

 the case stands, the probability is that the limestone is to the 

 bottom true coral-reef rock and that the depth to which it ex- 

 tends is, therefore, a measure of actual subsidence. 



Darwin's Coral Island theory. — In the above statements 

 the present condition of Darwin's theory of Coral Islands, is 

 fully and fairly recognized. Much has been recently written 

 about the theory's having been set aside or proved to be without 

 foundation. But in truth, no facts have been published that 

 prove the theory false, or set aside the arguments in its favor. 

 The facts and arguments from Tahiti brought out by Mr. 

 Murray I have shown, in my review of the subject in this 

 Journal in 1885* (published also at the same time in the Lon- 

 don Philosophical Magazine), to have no weight and more than 

 this, to sustain Darwin's theory, instead of opposing it. The 

 idea of the excavation of the lagoon-basins of coral islands by 

 sea- waters I have also proved in the same paper to be not a 

 possibility. 



The only suggestion of real importance that has been pre- 

 sented is not against Darwin's explanation, but simply in favor 

 of a possible substitute. Mr. A. Agassiz and others have sug- 

 gested that deep-sea organisms may build up limestone over the 

 sea-bottom, and thus raise the rock to the level where reef- 

 forming corals may grow, or within 100 to 150 feet of the sur- 

 face ; and that, in this way, coral reefs and islands may have 

 been formed without subsidence. Mr. Guppy has shown that 

 some coral-made limestone, in the southwest Pacific, actually 

 has a base of limestone that had been made by other life 

 than that of reef-corals. This is all the foundation for setting 

 aside Darwin's conclusions.. It is good ground for doubting, 

 and a good reason for investigating the nature of the coral 

 limestone in the various coral-reef regions of the Pacific at 



* Volume xxx, pp. 89 and 169. 



