134 Mr. Dana's Reply to Mr. Couthouifs Vindication. 



a general truth, which he is disposed to make it, wholly errone- 

 ous ; and is not even correct for the Samoa group, except it may- 

 be at some particular season of the year. "When the surface 

 temperature is 75°, the temperature at a depth of thirteen fath- 

 oms will be much below this. 



Mr. Couthouy states that at the Sandwich Islands the tempe- 

 rature "is as high sometimes as 81°," but strangely neglects to 

 add that it is as low sometimes as 68° F. This be it remem- 

 bered, is " in the Polynesian seas," (see the paragraph cited on 

 a preceding page.) 



In view of so many errors and hasty conclusions, is it not most 

 charitable to suppose that Mr. C. never made any observations 

 with reference to this subject ? for I know his zeal too well to 

 believe without good evidence, that he would otherwise have 

 been so superficial and inaccurate. But supposing his facts true, 

 what do they prove ? That 76° is the flourishing temperature, 

 or as he expresses his belief on page 384, Yol. xlv, of this Journal, 

 that wherever this temperature of 76° exists, there corals will be 

 found to flourish in the utmost profusion ? Why not as well 77°, 

 or 78°, or 79°, or 80° ? All the temperatures given, are above 

 76°, and it would be the most probable conclusion from them, 

 that if there is a flourishing temperature, it is the mean of the 

 whole, or 79£°. 



Perhaps however he wishes his more general assertion receiv- 

 ed, instead of the one here dwelt upon, namely, that where 

 the temperature is not below 76°, there they will flourish as 

 in the Polynesian seas. But we will not tire the reader with 

 needless words. I merely add, that on the coast of New Cale- 

 donia, in latitude 20°, where coral reefs are so extensive, the 

 temperature falls at certain seasons to 73°. 69° was the average 

 for the month of February at the Sandwich Islands, {one of the 

 Polynesian groups,) as obtained by the Exploring Expedition. 

 A writer states that near the Bermudas in 1837, the temperature 

 of the sea in December fell to 67|°. The General Report on 

 the temperature of the ocean by Capt. Wilkes, will throw much 

 light on this subject, and we now leave it, as my readers are prob- 

 ably fully satisfied, that whether Mr. Couthouy intended to give 

 76° as the limiting ox flourishing temperature, he is in something 

 of an error. 



I would not say that 76° is not the temperature best suited for 

 corals. I advance no opinion on the subject. It requires more 



