i8 NATURAL SCIENCE. July. 



wider problems of the permanence of ocean basins and general 

 world-architecture, they have been provided with new and important 

 documents. All these questions have already been fully discussed in 

 Natural Science by persons competent to express an opinion. 

 In our first number the Report on Deep-sea Deposits was reviewed 

 at length by Mr. Harris Teall, and the exploration of coral-reefs was 

 dealt with by Dr. J. W. Gregory. In August, 1892, Dr. Russel 

 Wallace criticised the views as to the permanence of ocean basins 

 that Mr. John Murray had based on the work of the " Challenger " ; 

 while Professor Edward Suess was so good as to give English readers 

 his opinions on the same subject in our number for March, 1893. 

 We have now asked Professor Judd to set forth the present answer 

 of geologists to the questions concerning coral-reefs raised by the 

 " Challenger " Expedition ; and, as circumstances have unfortunately 

 prevented the Abbe Renard from fulfilling his promise to contribute, 

 two of Mr. Murray's fellow-workers have most kindly supplied notes 

 on the deep-sea deposits and the problems they have raised. 



Coral-Reefs. 



Previously to the expedition of the " Challenger," two naturalists 

 had expressed doubts as to the universal application of the " sub- 

 sidence-theory " of coral-reefs — a theory first propounded by Darwin, 

 and afterwards very ably supported by Dana. In 1863, Semper 

 showed that, in the Pelew Islands, there are found in close proximity 

 to one another upraised reefs and atolls ; while J.J. Rein, in 1870, 

 argued that the phenomena displayed in the Bermudas point to 

 far more complex conditions than those postulated in the theory of 

 subsidence. 



It is an unquestionable fact, however, that it was mainly owing 

 to the important observations made on board the " Challenger " with 

 respect to the nature and mode of accumulation of the deep-sea 

 organic deposits, that a wide-spread feeling of doubt as to the adequacy 

 of the subsidence-theory of Darwin began to be manifested among 

 zoologists, and to a less extent among geologists also. It is not 

 necessary, here, to detail the various contributions to this important 

 question made by Dr. John Murray, and subsequently by Prof. A. 

 Agassiz and other zoologists. A very clear and impartial statement of 

 the arguments adduced on either side of the question, down to the year 

 1889, will be found in the appendix drawn up by Professor Bonney for 

 the third edition of Darwin's " Coral-Reefs." Since 1889 there have 

 appeared two other very important works dealing with the whole 

 question, namely, the third edition of Dana's " Corals and Coral- 

 islands," and Dr. Langenbeck's " Die Theorien iiber die Entstehung 

 der Koralleninseln und Korallenriffe und ihre Bedeutung fur Geophy- 

 sischen Fragen." 



The geological bearings of the observations made upon existing 

 coral-reefs have been made the subject of several important memoirs, 



