xi v PREFA TOR Y NO TE. 



subsidence of the beds of the great oceans, and if this has not 

 affected the forms of the coral-reefs.' The second note of 

 dissent was sounded in 1870, when J. J. Rein 1 published some 

 observations on the Bermuda Islands, and considered that they 

 could be explained on the grounds of an extension upwards of 

 accumulations of calcareous sediment from the sea-bottom ; 

 this contribution to the subject Darwin did not mention in his 

 second edition, and, probably, it escaped him : it has, however, 

 been contradicted by the more recent observations of Professor 

 Rice in 1884, and Professor Heilprin in 1889. 



The greatest contribution to the controversy has been 

 rendered by Dr. J. Murray, who, after his return from the 

 Challenger Expedition (to which he acted as naturalist), read, 

 on April 5, 1880, a paper" before the Royal Society of Edinburgh 

 which has entirely revolutionised the scientific concepts of 

 coral-reef formation, and modified to no small degree in the 

 minds of thinking geologists the theory which Darwin pro- 

 mulgated of the polypes building reefs on areas of subsidence. 

 He has pointed out that barrier-reefs do not by themselves 

 prove depression, since their bases may be and are formed of a 

 talus of their own debris produced by wave-action, and that, 

 where such a condition obtains, they appear at first sight to 

 consist of a solid, calcareous, coral-like substance which had been 

 secreted by the polypes in the exact locality where they are 

 now found, and on a bed which had undergone depression. 

 He has further shown that those islands which are fringed by 

 reefs do not give any evidences of gradual subsidence, and he, 

 moreover, states that, in his opinion, were the platforms, on 

 which the reefs are built, remnants of a pre-existent continent 

 which has been submerged beneath the waves, then it would 

 be expected to find traces of strata, other than volcanic, on 

 their flanks ; and this it is known is not the case, since 

 the only rocks found are lavas and tufas. Again, it is a 

 well-known fact that volcanic action takes place on the 



1 Senckenburg, Naiurf. Gesellsch. Wiirzburg, 1869-70, p. 157. 



2 Proc. Roy. Soc. Edin., 1880, p. 505; and Article "Pacific" in 

 Encyclopedia Britannica, voL xviii. pp. 128, 129. 



