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of the earth's surface, the analogies between the modern igneous 

 rocks and the so-called primary formations, on erosion, on denuda- 

 tion in the Pacific, on terraces, and the formation of valleys. Further, 

 he was an active field geologist, and more especially studied the so- 

 called Taconic system, chiefly in Western New England, and the 

 glacial phenomena of Southern New England. The region included 

 in Western Connecticut and Massachusetts, and extending west- 

 ward into New York, and north to Vermont, was traversed many 

 times, and there was scarcely an outcrop in the whole of this difficult 

 region which was not visited by him, and carefully examined and 

 described. His geological report for the Wilkes expedition occupies 

 756 pages, and is accompanied by 21 plates. Farther, he was particu- 

 larly interested in volcanoes, and in 1890 published a considerable 

 work (399 pages) entitled " Characteristics of Volcanoes, with Con- 

 tributions of Facts and Principles from the Hawaiian Islands," which 

 placed on record much useful information collected by him during 

 his travels in volcanic regions. 



His zoological work, which was even more extensive than that in 

 mineralogy and geology, chiefly related to the Wilkes expedition of 

 1838 1842. This expedition followed in part the course taken by 

 the " Beagle," in 1831 1836, and even where it diverged from that 

 route, visited coral and volcanic islands, such as have been carefully 

 described by Charles Darwin. When the Wilkes expedition reached 

 Sydney, in 1839, Dana chanced to see in a newspaper there a state- 

 ment of Darwin's theory of the origin of the atoll and barrier forms 

 of reefs. This statement, though very brief, was so suggestive as to 

 be of great help to him in his work, and he ever afterwards expressed 

 feelings of the deepest gratitude to its author. A visit to the Fiji 

 Islands in 1840 (where two of his colleagues were murdered by the 

 natives) brought before him facts such as had been noticed by Darwin 

 elsewhere ; but in the Fiji Islands they were on a still grander scale, 

 and of a more diversiBed character, thus enabling him to speak even 

 more positively of the theory than Darwin himself had thought it 

 philosophical to do. One large volume of his expedition report was 

 devoted to zoophytes, and described over 200 new species. His 

 report on the Crustacea occupied two volumes, and described 680 

 species, of which more than 500 were new to science. Each volume 

 was illustrated by an atlas of beautiful plates, most of them drawn 

 by himself. Though the last half -century has brought some slight 

 changes to his classification of the Crustacea, that of the corals stands 

 to-day nearly as it was given by him in the report. This was the 

 first time that any considerable number of the coral animals had been 

 described and figured from life. Dana further showed that the reef- 

 building corals live only in water having a temperature of at least 

 68 F., and that the distribution of the corals thus depends on the 



