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On the Temperature limiting the Distribution of Corals. By 

 James D. Dana, Geologist of the United States Exploring 

 Expedition. Read before the Association of American Geo- 

 logists and Naturalists, at Albany, April 29, 1843. 



I have before stated to the Association, that the temperature 

 limiting the distribution of corals in the ocean is not far from 

 66° F. On ascertaining the influence of temperature on the 

 growth of corals, I was at once enabled to explain the singular 

 fact, that no coral occurs at the Gallapagos, although under 

 the Equator, while growing reefs have formed the Bermudas in 

 latitude 33°, four or five degrees beyond the usual coral limits. 

 Injustice to myself, I may state here, that this explanation, 

 which was published some two years since by another, was origi- 

 nally derived from my manuscripts, which were laid open most 

 confidingly for his perusal, while at the Sandwich Islands in 

 1840.* The anomalies which the Gallapagos and Bermudas 

 seemed to present, were dwelt upon at some length in the 

 manuscript, and attributed in the latter case to the influence 

 of the warm waters of the Gulf Stream ; in the former to the 

 southern current up the South American coast, whose cold 

 waters reduce the ocean temperature about the Gallapagos to 

 60° F. during some seasons, although twenty degrees to the 

 west, the waters stand at 84° F. Extratropical currents, like 

 that which flows by the Gallapagos, are found on the western 

 coasts of both continents, both north and south of the Equator, 

 and intratropical currents are as distinctly traceable on the 

 eastern coasts, t In consequence of these currents, the coral 

 zone is contracted on the western coasts and expanded on the 

 eastern ; it is reduced to a width of sixteen degrees on the 

 western coast of America, and of but twelve degrees on the 



* The publication here alluded to, we understand, refers to an Article, by Mr 

 J. P. Couthouy, which appeared last year in the Boston Journal of Natural His- 

 tory. 



t The existence of these great oceanic currents was first pointed out to mc by 

 our distinguished meteorologist Mr William C. Redfield, who kindly furnished 

 me with charts of the same before the sailing of the Expedition. 



