the Geographical Distribution of Marine Species. 319 
of them which the pt authors afford us, and to some conclusions 
flowing from the fae 
n the Atlantic, a warm tropicai current flowing westward, 
is trended somewhat northward by the northern coast of South 
America, and still more so by the West en Islands, and thus it 
gradually curves around to parallelism with the coast of the 
United States. But south of Newfoundland, either wholly from 
the influence of the colder current with which it meets, or in 
in the isocrymes of 74° and 68° F., near the United States coast, 
thus have their origin. For the same reason, the line of 56° PF. 
is nearly straight, till it reaches beyond the influence of the New- 
foundland pe and then makes its Gulf Stream flexure. The 
line of 44° F, for ‘the same reason,—the spreading of the Gulf 
of the Gulf Stream flexure. So on the western coast of Britain, 
the isocryme of 44° F, has a deep southern flexure, for a like 
The waters of the tropical current gradually cool down in their 
~~ through the influence of the colder waters which they 
unter; and along the isocryme of 62°, they have in the 
n 
a mean temperature. Owing to the influence of the polar current 
on the northern coast of South America, the equator of heat lies 
at a distance from the land. 
p the western coast of ‘Africa flows the cold current from the 
south and west, bending upward all the isocrymal lines ; and 
passing north of the equator, it produces a large southern bend, 
off the coast of Africa, in the northern isocryme of 74° outside of 
the warm current preci from the coast of Guinea, and also a 
large northern flexure in the heat-equator.* 
The Atlantic eeopleall current also flows in part down the eastern 
a hie South America, giving a deep flexure to each of the iso- 
s, besides making these lines to diverge from the equator, 
daoiek all their length. Again, the polar current passes north- 
* Along the ocean, near Africa, south and southeast of the Cape Verdes, Captain 
MS yaw found a eyed ieiiee to the northward for much of the time until passing 
oqne 
