in the Pacific, S^c. 161 



At the Cape Verde Islands, and in the neighborhood of 

 Trinidad, Martin Yas, and Fernando Noronha, it falls to 69° 

 and 71° ; and these islands, as was before remarked, are en- 

 tirely destitute of coral formations. It is not unlikely that 

 there are cold currents from the Antarctic along the East £is 

 well as the West coast of South America, which combine 

 with the fresh water of its large rivers in preventing such 

 formations upon a certain portion of it, but this I have at 

 present no means of determining, being without any data as 

 to the temperature north of 35° on that side. It appears to 

 me, that such coincidences as the facts here submitted prove 

 to exist, between certain temperatures of the ocean and the 

 absence 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 absence of recent coral formations 

 in certain regions corresponding in every thing save tempera- 

 ture to those where they are most profusely scattered. In or- 

 der 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 observations on the oceanic temperatures at the surface and 

 to certain depths, along both sides of the African continent, 

 the coasts of Australia, and among the coral archipelagos of 

 the Indian seas ; together with that of the seas beyond the 

 limits of such formations, in both hemispheres. Such obser- 

 vations might easily be made on board our national vessels, 

 by direction of the Navy Department, and published in the 

 form of tabular reports at the expiration of their cruise. The 

 Department would, I presume, scarcely refuse to issue the 

 requisite instructions, upon suitable representation. There 

 are also many intelligent commanders in our merchant service, 

 who only require that their attention should be directed to 

 this matter, in order, as I am confident, to ensure their cordial 

 cooperation. By the mass of information which would thus 

 be brought together we might also expect that much light 

 would be thrown on questions relative to oceanic and (as con- 

 nected with these,) atmospheric phenomena, our knowledge 



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