16 
TIIH U UU-STIIEAM. 
a contrary direction in the motion of the waters. 'Within 
^e. tropics, especially from the coast of Senegal to the 
Caribbean Sea, the general current, that which was earliest 
known to mariners, flows constantly from east to west. 
This is called the equinoctial current. Its mean rapidity, 
corresponding to diflerent latitudes, is nearly the same in. 
the Atlantic and in the Pacific, and may be estimated 
at nine or ten miles in twenty-four hours, consequently 
from 0 59 to O' (Jo of a foot every second ! In those lati- 
tudes the waters run towards the west with a velocity 
equal to_a fourth of the rapidity of the greater part of the 
larger rivers of Europe. The movement of the ocean in a 
direction contrary to that of the rotation of the globe, is pro- 
bably connected with this last phenomenon only as far as the 
rotation converts into trade winds* the polar winds, which, 
in the low regions of the atmosphere bring back the cold air 
of the high latitudes toward the equator. To the gene- 
ral impulsion which these trade-winds give the surface of 
the sea, avo must attribute the equinoctial current, the force 
and rapidity of which are not sensibly modified by the local 
variations of the atmosphere. 
In the channel which the Atlantic has dug between Guiana 
and Guinea, on the meridian of 20 or 23 degrees, and from 
the 8th or 9th to the 2nd or 3rd degrees of northern lati- 
tude, where the trade-winds arc often" interrupted by winds 
blowing from the south and south-south-west, the equinoc- 
tial current is more inconstant in its direction. Towards 
the coasts of Africa, vessels are drawn in the direction of 
south-east ; whilst towards the Bay of All Saints and Cape 
St. Augustin, the coasts of which are dreaded by navigators 
sailing towards tlio mouth of the Plata, the general motion 
ot the waters is masked by a particular current (the effects 
of which extend from Cape St. Koche to the Isle of Trinidad) 
running north-west with a mean velocity of a foot and a 
half every second. 
The equinoctial current is felt, though feebly, even beyond 
the tropic of Cancer, in the 26th and 28th degrees of' lati- 
tude. In the vast basin of the Atlantic, at six or seven 
hundred leagues from the coasts of Africa, vessels from 
Europe hound to the West Indies, find their sailing aecele- 
* The limits of the trade winds were, for the first time, determined by 
Dan: pier in 1666. 
