82 THE GREAT BARRIER REEF. 



it is gen erall}' distinguished by the title of the "subsidence theory," and as such is hereafter 

 referred to. 



Among the more eminent authorities on the subject of coral-reefs, who have been afforded an 

 opportunity of putting Mr. Darwin's theory partly to the test, mention must be made of James D. 

 Dana, Professor of Geology and Minerology in Yale College, U.S.A. His name will ever be 

 associated with one of the finest illustrated works on the subject of corals and coral-animals 

 such being the nature of his magnificent folio Report on the Zoophytes of the Wilkes U.S. 

 Exploring Expedition, published by the United States Government. This expedition, to which 

 Professor Dana was attached as zoologist and geologist, was conducted between the years 1838 

 and 1842, and covered much of the ground previously visited by Mr. Darwin. A compendious 

 resume of all the leading features of the larger work, together with a masterly account of subse- 

 quently-acquired data, bearing on the same subject, is embodied in the smaller work, entitled 

 "Corals and Coral Islands," published b}' the same author in the year 1872. Professor Dana's 

 thoughts on Darwin's subsidence theory may be cited in his own words from the last-named 

 work. — 



" Our cruise led us partly along the course followed by Mr. Charles Darwin during the years 

 1831 to 1836, in the voyage of the Beagle, under Captain Fitzroy ; and, where it diverged from 

 his route, it took us over scenes, similar to his, of coral and volcanic islands. Soon after reaching 

 Sydney, Australia, in 1839, a brief statement was found in the papers of Mr. Darwin's theory 

 with respect to the origin of the atoll and barrier forms of reefs. The paragraph threw a flood of 

 light over the subject, and called forth feelings of peculiar satisfaction, and of gratefulness to Mr. 

 Darwin, which still come up afresh whenever the subject of coral islands is mentioned. The 

 Gambler Islands, in the Paumotus, which gave him the key to the theory, I had not seen ; but on 

 reaching the Fijis, six months later, in 1840, I found there similar facts on a still grander scale 

 and of more diversified character, so that I was afterwards enabled to speak of his theory as 

 established with more positiveness than he himself, in his philosophic caution, had been ready 

 to adopt." 



In his general summary of the abundant evidence he adduces in support of the subsidence 

 theory, as applied to the coral-reef area he personally investigated, Professor Dana sums up as 

 follows : — 



" What is the extent of the subsidence indicated by the coral-reefs and islands oj the Pacific 1 It is very evident that 

 the sinking of the Society, Samoan, and Hawaian Islands has been small compared with that required to submerge all 

 the lands on which the Paumotus and the other Pacific atolls rest. One, two, or five hundred feet could not have 

 buried the many peaks of these Islands. Even the 1,200 ft. of depression at the Gambier group is shown to be at a 

 distance from the axis of the subsiding area. The groups of high islands, above mentioned, contain summits from 4,000 to 

 14,000 feet above the sea, and can we believe it possible that throughout this large area, when the two liundred islands 

 now sunken were above the waves, there were none of them equal in altitude to the mean of these heights, or g,ooo 

 feet ? That none should have exceeded 9,000 feet in elevation is by no means probable. Hence, however moderate the 



