124 



THE POPULAR SCIENCE MONTHLY. 



Mr. Atkinson and Prof. Mattieu Will- 

 iams are working in this field, and that 

 their results are received with interest, 

 gives promise that the human race will 

 some time attain to a thoroughly intelli- 

 gent style of daily life. 



LITERARY NOTICES. 



The Structure and Distribution of Coral 

 Reefs. By Charles Darwin. Third 

 Edition, with an Appendix by Prof. T. G. 

 Bonnet. With Illustrations, New York: 

 D. Appleton & Co. Pp. 344. Price, $2. 



The formation of coral reefs was one of 

 the subjects investigated by Darwin during 

 the voyage of the Beagle. The information 

 which he obtained from his own observations 

 and the reports of other investigators, to- 

 gether with the mode of accounting for these 

 structures resulting from his study of this 

 material, are embodied in the present work. 

 The first edition of the book was published 

 in 1842, a brief sketch of the author's views 

 having been read in 1837 before the Geologi- 

 cal Society, of London, and published. Dar- 

 win's theory of coral reefs speedily won ac- 

 ceptance among men of science, and had 

 been taught in scientific lectures and text- 

 books for a generation before any consider- 

 able rival appeared. In 1874 Darwin issued 

 a revision of his book, containing additional 

 facts obtained by later explorers. The only 

 important work on the subject which had 

 appeared since 1842 was Prof. James D. 

 Dana's " Corals and Coral Reefs," issued in 

 1872. Prof. Dana had accepted Darwin's 

 theory in the main, though objecting very 

 decidedly to some of its minor features. In 

 18S0 Mr. John Murray, one of the natural- 

 ists of the Challenger Expedition, advanced 

 a theory widely at variance with that of 

 Darwin, which has found vigorous support- 

 ers, and various modifications of both the 

 leading hypotheses have been offered by later 

 investigators. But the majority of those 

 qualified to judge of this difficult question 

 have shown a disinclination to give up Dar- 

 win's theory for that of Murray so much 

 so that the Duke of Argyll, evidently jealous 

 for Scottish honor, in 1887 accused scientific 

 men of disregarding Murray's work from 

 subserviency to their idolized Darwin. The 

 duke's article was entitled " A Conspiracy of 



Silence," and drew forth a vigorous reply 

 from Prof. Huxley in the review in which it 

 appeared, besides arousing a spirited discus- 

 sion in the columns of " Nature." The new 

 edition of " Coral Reefs " affords the means 

 of forming an intelligent opinion as to the 

 merits of Darwin's views. It is, by the way, 

 the first edition that has been published in 

 this country. The body of the work has 

 been left as revised by the author for the 

 second edition, but occasional foot-notes, and 

 an appendix comprising a careful summary 

 of the more important memoirs published 

 since 1874, have been added by Prof. T. G. 

 Bonney. In the first three chapters the 

 three chief classes of coral formations 

 atolls or lagoon islands, barrier reefs, and 

 fringing or shore reefs are described. The 

 fourth chapter deals with the distribution of 

 coral reefs and conditions favorable to their 

 increase, their rate of growth, and the depths 

 at which reef-building corals can live. Dar- 

 win's theory of the formation of the differ- 

 ent classes of coral reefs then follows. 

 Coral polyps do not flourish below a depth of 

 twenty or thirty fathoms, but reefs are found 

 rising from much greater depths how are 

 these to be accounted for ? The theory re- 

 gards barrier reefs and atolls as having been 

 developed successively from fringing reefs. 

 The latter are so named because they closely 

 skirt the shores of islands and continental 

 land, increasing by growth on the outer edge, 

 where the conditions seem to be most favor- 

 able for the life of the corals. Imagine such 

 a reef formed around a volcanic island, and 

 the island then to begin sinking beneath the 

 sea. The reef will be carried down with it, 

 but the active growth at the outer edge will 

 still keep this part at the sea-level, while the 

 inshore part where growth has stopped will 

 become deeply submerged. We now have 

 an island surrouuded by a deep channel, out- 

 side of which is a ring of coral that is, an 

 island encircled by a barrier reef. Suppose 

 the subsidence to go still further until the 

 highest point of the island disappears, the 

 growth at the outer edge of the reef still 

 keeping it up to the surface, and there re- 

 sults a ring-shaped reef inclosing a lagoon 

 that is, an atoll. It can not be denied that 

 this theory accounts for the channel within 

 a barrier reef and the ring shape of atolls, 

 besides answering the question asked above, 



