GEOGRAPHICAL DISTRIBUTION OF CRUSTACEA. 1461 



(latitude 34), Fitzroy found 55 to 61 F., while on August 16, farther 

 south, in 35 4' south, and 15 40' west, one hundred and fifty miles 

 from the Cape, Vaillant found the temperature 59'36 F. The high 

 temperature of the last is due to the warm waters that come from the 

 Indian Ocean, and which afford 61 to 64 F. in August, off the south 

 extremity of Africa, west of the meridian of Cape Town. 



The isocryme of 50 F. leaves the American coast just south of the 

 La Plata; after bending southwardly to the parallel of 41, it passes 

 east nearly parallel with the line of 56 F. It does not reach the 

 African coast. 



Isocrymes of 44 and 35 F. Fitzroy in August (the last winter 

 month) of 1833, found the sea-temperature at Rio Negro (latitude 41 

 south) 48J to 50 F. But during the voyage from the La Plata to 

 Rio Negro, a few days before, a temperature of 44 J to 46 was met 

 with ; this was in the same month in which the low temperature men- 

 tioned on a preceding page was found at Montevideo. The bend in 

 the coast north of the entrance to the La Plata, is to some extent, a 

 limit between the warmer waters of the north and the colder waters 

 from the south ; not an impassable limit, but one which is marked 

 often by a more abrupt transition than occurs elsewhere along this 

 part of the coast. The water was generally three or four degrees 

 colder at Montevideo, than at Maldonado, the latter port being hardly 

 sheltered from the influence of the tropical waters, while Montevideo 

 is wholly so. The exact point where the line of 44 F. reaches the 

 coast is somewhat uncertain, yet the fact of its being south of Rio 

 Negro is obvious. After leaving the coast, it passes north of 47i 

 south, in longitude 53 west, where Beechey, in July, 1828, found the 

 sea-temperature 40-70 F. 



The line of 35 F. through the middle of the South Atlantic, follows 

 nearly the parallel of 50 ; but towards South America it bends south- 

 ward and passes south of the Falklands and Fuegia. At the Falklands, 

 Captain Ross, in 1842, found the mean temperature of the sea for 

 July, 38-73, and for August, 38-10; while in the middle of the At- 

 lantic, on March 24, latitude 52 31' south, and longitude 8 8' east, 

 the temperature was down to 34'3 F., and in 50 18' south, 7 15' east, 

 it was 37 F.; March 20, in 54 7' south, on the meridian of Green- 

 wich, it was 33-4 F. The month of March would not give the cold- 

 est temperature. The temperature of the sea along the south coasts 



366 



