1482 CRUSTACEA. 



half degrees above the normal position in the Pacific. The line of 

 44° F. may be considered as having for its mean position the parallel 

 of 52° north, while it rises to 60° north. The lines in the North 

 Atlantic above that of 68°, average about five degrees higher in lati- 

 tude than the mean normal positions, while 68° and 74° have nearly 

 the same place as in the Pacific. There is hence a great contrast 

 between the Pacific, South Atlantic, and North Atlantic Oceans. 

 This is seen in the following table containing these results : 







Normal, deduced 



Mean position in 



Mean position in 







from Pacific. 



South Atlantic. 



North Atlantic. 



Isocryme 



of 74° F., 



20° 



7° south. 



21° north. 



a 



68° 



27° 



19° 



28° 



it 



62° 



32° 



29° 



36° 



a 



56° 



37° 



36° 



42 J° 



u 



50° 



42° 



39° 



47*° 



it 



44° 



47° 



44° 



52° (max. 60° north) 



u 



35° 



56° 



50° 



61° (max. — ?) 



The influence of the warm tropical waters in the North Atlantic 

 lifts the isocrymes of 74° and 68° as they approach the coast of 

 America, while "the same lines are depressed on the east by the colder 

 northern currents. Moreover, north of 68° the whole interior of the 

 ocean is raised four to five degrees in temperature above the normal 

 grade, by the same waters spreading eastward ; and between Great 

 Britain and Iceland, the temperature is at least ten degrees warmer 

 than in the corresponding latitude of the South Pacific, and thirteen 

 or fourteen degrees warmer than in the same latitude in the South 

 Atlantic* 



The influence of so warm an ocean on the temperature of Britain, 

 and on its living productions, animal and vegetable, is apparent, when 

 it is considered, that the winds take the temperature nearly of the 

 waters they pass over. And the effects on the same region, that 

 would result from deflecting the Gulf Stream in some other direction, 

 as remarked by Prof. Hopkinsf and others, and substituting in the 

 Northern Atlantic the temperature of the Southern Atlantic, is also 



* Ross, in his Antarctic Voyage, found the sea- temperature in 60° south and 3° west, 

 31 J° F., in the month of March; at the South Shetlands, 61° south, the sea-temperature 

 was 31° to 35° in January (midsummer); and in the same latitude, and 45° west, it 

 was 30-1° in February. 



f Quarterly Jour. Greol. Soc, vol. viii., p. 56, and Amer. Jour. Sci., 1853, vol. xv. 



