Mr. Dana's Reply to Mr. Couthouy's Vindication. 133 



it, most honestly ; and such is the obvious idea to be gathered 

 from the paragraph. However, a writer sometimes uses words 

 by mistake that do not express the idea intended, and such may 

 have been the fact in the case before us, although there might be 

 some reason for doubt, seeing that he gives no instance of a tem- 

 perature below 76° in any of the coral seas. Mr. Couthouy 

 would have us understand that 76° F. is not given as the limiting 

 temperature, but the flourishing temperature, and that where the 

 temperature is not below 76° F., corals will flourish, "as in the 

 Polynesian seas :" or, as he states in another place, that ° where 

 that exists (76° F.) l is the field of their most lavish display. .' " 

 But how does Mr. C. arrive at the fact that 76° is the most con- 

 genial temperature? On what accurate and extended series of 

 observations is this important deduction based ? 



He states that through the coral archipelago to the eastward 

 of Tahiti, the surface temperature ranges from 78° to 81°, (Bost. 

 Jour. p. 75.) The fact is that the range is from 77° to 83°, 

 and in the second part of his article printed at a later period, we 

 find this range given, (p. 100,) evidently a correction of the for- 

 mer from subsequent information, and not a part of his expedi- 

 tion observations. 



He says that the same is true "of the neighborhood of the de- 

 tached islets between Tahiti and Samoa." The correct range 

 for this region is from 75° to 81°. 



He states that at Tutuila in the Samoa group, the surface tem- 

 perature was 81°, and that at the bottom, in thirteen fathoms, 

 where the coral was growing profusely, was 76° : and adds, with 

 reference to this supposed fact and the others adduced, "that I 

 here intend to prove, that as throughout the archipelago, where 

 corals flourish in such perfection, the surface temperature is the 

 same as at the reef off Tutuila, so also is the temperature of the 

 bottom, i. e. 76°, is surely obvious, even without what here fol- 

 lows ;" after which he quotes the paragraph above cited, with 

 some additional facts which we notice below. 



With regard to the surface temperature at Tutuila, it ranges 

 from 75° to 82° ; and as to 76° being the temperature at the 

 bottom in thirteen fathoms where corals were growing,* it is, as 



* By referring to the log-book of the Vincennes, I find that no temperature was 

 taken at any depth on the reef here referred to. The thirteen fathoms was obtained 

 by a cast alongside of the reef; the reef itself on which the coral is growing varies 

 in depth from 4. J to 7 fathoms. (See Expedition charts, now publishing.) 



