Association of American Geologists and Naturalists. 125 



and in the wide space between it and the low islands of Polynesia, is 

 to be attributed to the prevalence of cold currents, which proceeding 

 northward from the polar regions are perceptible the whole distance 

 from Cape Horn to Callao, and I presume much further to the north, in 

 a temperature of the ocean too low for the existence of the coral ani- 

 mals, and that in a similar low temperature we are to seek for the cause 

 of their absence at the Cape Verd Islands"* and the other islands de- 

 signated in my article as destitute of coral formations. 



That I have never intended to claim more than is here set forth, is I 

 think manifest in the following extracts ; and if I have been otherwise 

 understood, the error is wholly attributable to my having defectively ex- 

 pressed ideas perfectly clear to my own mind, and thereby misled my 

 readers. 



" It appears to me, that such coincidences as the facts here submitted 

 prove to exist, between certain temperatures of the ocean and the ab- 

 sence or presence of coral reefs, can scarcely be considered by any 

 reflecting mind as merely casual ; and that there are strong grounds for 

 believing that we have here a clue to the real cause of the singular ab- 

 sence of recent coral formations in certain regions corresponding in 

 every thing save temperature to those where they are most profusely 

 scattered. In order to enable us, however, satisfactorily to determine 

 how far their geographical distribution is affected by such causes, it is 

 essential that we should be furnished with a connected series of obser- 

 vations on the oceanic temperatures at the surface and to certain depths, 

 along both sides of the African continent, the coasts of Australia, and 

 and among the coral archipelagos of the Indian seas, together with 

 that of the seas beyond the limits of such formations, in both hemi- 

 spheres."! 



" While convinced in my own mind of the truth of the suggestions 

 here offered in regard to the absence of coral formations in certain re- 

 gions, I feel conscious also that the data upon which they rest, though 

 certainly presenting a strong case as far as they extend, are after all 

 but limited in comparison with those still deficient. I submit them for 

 what they are worth. What this may be, time and more extensive ob- 

 servation must determine. Claiming only to have at least sought a more 

 rational mode of accounting for the peculiarities here pointed out, than 

 that of supposing them altogether fortuitous, I shall rejoice if the end 

 show that I have contributed in the slightest degree or in a single point 

 of view to the advancement of the great object to which we are all, ac- 

 cording to our opportunities, devoted. "| 



■' Bost. Jour. Nat. Hist., Vol. IV, pp. 159, 160. t lb. p. 162. t lb. p. 162. 



