160 On an Isothermal Oceanic Chart, illustrating 
expansion of the Gulf Stream in that direction, and forms a large 
fold between Britain and Iceland ; it then bends south again an 
curves around to the west coast of Ireland. 
Isocryme of 35° F.—This line has a bend between Norway 
and Iceland like that of 44°, and from the same cause,—the in- 
fluence of the Gulf Stream. But its exact position in this part 
as not been ascertained. . 
Sourn Ariantic.—Isocryme of 74° F.—This line begins 
just south of Bahia, where Fitzroy found in August (the last win- 
er month) a temperature of 74° to 753° F. During the same 
month he had 754° to 763° F. at Pernambuco, five degrees to 
the north. Off Bahia, the temperature was two degrees warmer 
than near the coast, owing to the warm tropical current, which 
bends the isocryme south to latitude 17° and 18°, and the cold 
waters that come up the coast from the south. The line gradu- 
ally rises northward, as it goes west, and passes the equator on 
the meridian of Greenwich. Sabine, in a route nearly straight 
from Ascension Island, in 8° south, to the African coast under 
the equator, obtained in June (not the coldest winter month) the 
temperatures 78°, 77°, 74°, 728°, 72-5°, 73°, the temperature 
thus diminishing on approaching the coast, although at the same 
time nearing the equator, and finally reaching it within a few 
miles. ‘These observations in June show that the isocryme of 
7A° EF’. passes north of the equator. The temperatures mentioned 
in Maury’s Chart afford the same conclusion, and lead to its posi- 
tion as laid down. : 
Isocryme of 68° F.—On October 234 to 25th, 1834, Mr. D. J. 
Browne, on board the U.S. Ship Erie, found the temperature of 
the sea on entering the harbor of Rio Janeiro, 674° to 683° F. 
Fitzroy on July 6, left the harbor with the sea temperature 703° 
eechey, in August, 1825, obtained the temperature 68°16° 
to 69°66° F’. off the harbor. The isocryme of 68° F. commences 
therefore near Rio, not far south of this harbor. Eastward of the 
west. The isocryme of 68° F. thus bends far south, reaching at 
least the parallel of 30°. It takes a course nearly parallel with the. 
line of 74° F., as different observations show, 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 683° near St. Helena; and Vaillant, in the Bonite, in Septem- 
ber found the sea-temperature 68-7° to 69-269 F. 
Tsocrymes of 56° and 50° F.—T hese 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 
