200 J. D. Dana on an Isothermal Oceanic Chart, 



August 20, Vaillant, in 33° 43' south, 15° 51' east, found the 

 temperature 56° F. ; while on the 22d, in the same lati- 

 tude, and 14° 51' east (or one degree farther to the westward), 

 the temperature was 57*74° F,, being nearly two degrees 

 warmer. At Cape Town, in June (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 26° 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 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) 48^° to 50° F. But during the 

 voyage from the La Plata to Rio Negro, a few days before, 

 a temperature of 44^° to 46° was met with ; this was in the 

 same month in which the low temperature mentioned above 

 was found at Montevideo. The bend in the course 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 Monte Video than at Maldonado, 

 the latter port being hardly sheltered from the influence of 

 the tropical waters, while Monte Video 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 47£° south, in longitude 53° west, where Beechey, in July 

 1828, found the sea-temperature 4070° 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 southward and passes south of the Falk- 



