illustrating the Distribution of Marine Animals. 199 



F. Beechey in August obtained 68° F. in 31° south, 46° west. 

 The isocryme of 68° F. thus bends far south, reaching at least 

 the parellel of 30°. It takes a course nearly parallel with 

 the line of 74° F., as different observations shew, and passing 

 just south of St Helena, reaches the African coast, near 

 latitude 7° south. Fitzroy, on July 10 (mid-winter), had a 

 sea-temperature of 68|-° near St Helena ; and Vaillant, in 

 the Bonite, in September found the sea-temperature 68*7° 

 to 69-26 F°. 



Isocrymes of 56° and 50° F. — These two isocrymes leave 

 the American coast rather nearly together. The former 

 commences just north of the entrance of the La Plata. 

 Fitzroy, in July 23 to 31, 1832, found the sea-temperature 

 at Monte Video 56° to 58° F., and in August, 57° to 54£° F. 

 These observations would lead to 56° F. as nearly the mean 

 of the coldest month. The temperature 56° F. was also ob- 

 served in 35° south, 53° west, and at 36° south, 56° 36' west. 

 But on July 10 and 13, 1833, at Monte Video, the sea-tem- 

 perature was 46£° to 472°, a degree of cold which, although 

 only occasional, throws the line of 56° F. to the north of this 

 place. The temperature near the land is several degrees of 

 Fahrenheit lower than at sea three to eight degrees distant. 

 East of the mouth of La Plata, near longitude 30° west, 

 Beechey, in July 1828, found the temperature of the sea 

 61-86° F. So in April 23 to 29, Vaillant obtained the tem- 

 perature 59-5° to 61-25° F. at Monte Video, while in 35° 5' 

 south, 49° 23' west, on April 14, it was 66-2° F.; and farther 

 south, in 37° 42' south, 53° 28' west, April 30, it was 64-4° F. ; 

 and in 39° 19' south, 54° 32' west, on May 1, it was 57f ° F. ; 

 but a little to the westward, on May 2, in 40° 30' south, 56° 

 54' west, the temperature was 48° F., an abrupt transition 

 to the colder shore waters. Beechey, in 39° 31' south, 45° 

 13' west, on August 28 (last of winter), found the tempera- 

 ture 57-25° F., and on the 29th, in 40° 27' south, 45° 46' 

 west, it was 54-20° ; while on the next day, in 42° 27' south, 

 45° 11' west, the temperature fell to 47-83° F. These and 

 other observations serve to fix the position of the isocryme 

 of 56° F. It approaches the African coast in 32° south, 

 but bends upward, owing to cold waters near the land. On 



