Theory of Marine Currents. 163 
one side, we will notice, in like manner, that the current 
which ascends along the heated side, and descends along the 
opposite side, forms a circuit, the interior part of which 
scarcely partakes in the agitation of the current which sur- 
rounds it. Casting our eyes on M. Duperrey’s chart, we im- 
mediately perceive, in the five circuitory oceanic basins, that 
the greatest intensity of the currents is principally towards 
their limits, and that the five intermediate spaces are left 
undisturbed, as they would have led us to suppose a priori. 
The following, then, are the five great circuits ; the first, 
in the Northern Atlantic, runs from Africa to the Gulf of 
Mexico by the equator, and returns by the Gulf Stream, and 
its derivatives to Europe and Africa, completing its return 
to the point of departure in about three years. The second, 
in the Southern Atlantic, is bounded by the west coast of 
Southern Africa by the equator, by the eastern side of South 
America, and, lastly, by a line running from the southern 
point of America to the southern point of Africa. The third 
circuit occupies the northern part of the Pacific Ocean, and 
even involves a considerable part of the waters lying be- 
tween the equator and the southern tropic. The fourth cir- 
cuit, situate in the southern part of the same ocean, takes its 
departure from the west coast of South America, and is 
bounded by the southern tropic, New Holland, below which 
it descends to the south in such a manner as to turn round 
New Zealand, and then reverts towards America. The fifth 
and last circuit occupies almost the whole of the Indian Sea, 
with the exception of the part nearest to Asia, which, from 
this want of circulation, is found to have the highest tempera- 
ture of all the intertropical seas. This circuit, bounded on 
the south by the parallel of the Cape of Good Hope, appears 
to be restricted from north to south within narrow limits, 
and the continual predominance of the current produced by 
the blowing of the monsoons on the permanent currents, ad- 
mitted by M. Duperrey, indicates a small degree of activity in 
the circulation of the waters of the fifth circuit. 
We do not speak of the currents which must necessarily 
establish themselves between these different basins, inde- 
pendently of the cireuitory movement which constitutes the 
