Ix PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The following instances, taken from the many made on different 

 voyages of discovery, will suffice to illustrate this fact : — 



Temperatures of the Atlantic. 



Latitude. 



Longitude 



(corrected 



to Greenwich). 



Depth. 



ft. 



4688 

 8399 

 3030 

 6037 



Temperature. 

 Surface. Bottom. 



Observer & Date. 



42 ON. 

 29 ON. 



7 21 N. 

 4 25 N. 



34 40 W. 

 34 50 W. 

 20 40 W. 

 26 6 



62-0 

 760 

 80-0 



80-8 



44-0 F. 

 430 

 36-0 

 37-9 



Chevalier 



Lenz 

 Tessan 



1837. 



1832. 

 1841. 



15 3S. 



25 10 S. 

 29 33 S. 

 32 20 S. 

 38 12 S. 



23 14 W. 



7 59 E. 

 10 57 E. 

 43 50 E. 

 54 80 W. 



7200 

 5315 

 6310 



6444 

 2000? 



77-0 

 67-4 

 66-4 

 71-0 

 62-4 



39-5 

 37-6 

 35-8 

 36-5 

 37-6 



Lenz 

 Tessan 



1832. 



1841. 



In the Antarctic regions Sir James Ross made a considerable 

 number of observations in 1839-43. Whatever the temperature of 

 the surface, he found the temperature from 2800 to 3600 feet to 

 be from 38"^ to 39-8°, the higher temperature being at the lower 

 depth. He concluded that below 1800 feet there was very little 

 variation in temperature, and inferred that in lat. 56° 14' S. there 

 is an ocean belt, the temperature of which from top to bottom is of 

 39-5°. This conclusion seems to have been based on an erroneous 

 idea of the specific gravity of sea-water, and is possibly in some 

 degree attributable to errors of the instruments used. Captain 

 WilKs, however, came to the same conclusion with respect to a belt 

 of uniform temperature. I cannot find that there is any sufficient 

 foundation for this hypothesis, which is in no way confirmed by the 

 observations of others. As the other observations were not generally 

 known, this hypothesis has unfortunately been too often accepted. 

 Later experience has shown that in many instances there is an 

 error in the earlier observations, in consequence (where proper 

 precautions were not used) of the pressure on the thermometer at 

 great depths. Dr. Carpenter has determined this to amount to as 

 much as 2° or 3°, or even more. Consequently a deduction to this 

 extent has often to be made in order to get a true reading of some 

 of the older observations. In many of the French expeditions, 

 however, great care was taken to guard against the influence of 

 pressure. 



If we turn to the Pacific, we shall find similar low temperatures 

 prevailing at great depths both in the temperate and torrid zone. I 

 again take merely a few cases in illustration. 



