SPECIFIC GRAVITY OF SEA WATER. 427 



The considerable nirmber of observations (there 

 are one hundred and sixteen of them) on the tem- 

 perature of the sea below the surface, their extent 

 over waters of the ocean remote from each other, and 

 probably, also, their accuracy, give them a decided 

 claim to the attention of the natural philosopher ^ 

 and the perseverance with which they were con- 

 tinued, luider various circumstances, does honour 

 as well to the Naturalist of the Expedition, as to 

 the commander, who not only in calms, but in 

 some periods, almost daily, afforded the necessary 

 assistance. They were all made with the Six-ther- 

 mometer *, which is a good assurance of their ac- 

 curacy. It is certainly remarkable, that an instru- 

 ment so simple, so convenient in the use, so 

 certain in the results, and which has been long 

 known, is not more frequently used for this pur- 

 pose ; so that in the latest scientific voyages, 

 much more uncertain thermometers have been 

 used, to which only the deep sea clamm of Captain 

 Ross forms an exception. 



Our observations fall under two heads : measure- 

 ments of the temperature in different de])ths, in 

 the same places of the ocean, and in statements 

 of the warmth in the usual soundings, from sixty 

 to eighty fathoms, in different places. 



The most complete observations on the changes 



* This instrument was divided, after the English manner, in 

 degrees of Fahrenheit : I have reduced the result to degrees 

 of lleaunmr. 



