THE 



AMERICAN JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



Aet. XII. — Origin of Coral Reefs and Islands; by James D. 

 Dana. With a map (Plate II). 



The Presidential Address of Dr. Archibald Geikie, Di- 

 rector-General of the Geological Survey of Great Britain, 

 before the Royal Physical Society of Edinburgh in 1883,* 

 reviews the subject of the origin of coral reefs and islands. In 

 the course of the discussion, the author sustains and enforces the 

 objections which have been presented by others, and concludes 

 that " the existence of such reefs is no more necessarily depen- 

 dent on subsidence than on elevation." The existing state of 

 doubt on the question has led the writer to reconsider the 

 earlier and later facts, and in the following pages he gives his 

 results. f That both sides may be fairly before the reader, the 

 views of Darwin and the evidences in favor of his theory are 

 first considered, and afterwards the arguments that have been 

 urged against it. Part of the objections are based on misun- 

 derstandings of the facts, and hence a general presentation of 

 the subject has been thought necessary. 



* Proceedings Edinb. Roy. Phil. Soc, viii, 1, 1883. 



f The writer's account of his original observations is contained in his "Wilkes 

 Expedition Geological Report, 1849 (756 pp. 4to), pages 29-154; and, less com- 

 pletely, along with a review of facts from other regions, in his Corals and Coral 

 Islands, 398 pp. 8vo, 1872, 1875. 



Am. Jour. Sci.— Third Series, Vol. XXX, No. 176.— August, 1885. 

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