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The National Geographic Magazine 



sprinkled with powder in order to ren- 

 der its motion visible. As soon as the 

 artificial wind was brought into action, 

 a drift was created, and the first tend- 

 ency was for the water to flow from all 

 sides into the rear of the drift. This 

 gradually extended itself in a sheaf-like 

 form , the marginal threads in the fields 

 untouched or only occasionally touched 

 by the air current leaving the main 

 bod j', first branching out to the right 

 and left, then reversing their motion, 

 and finally again working round to the 

 rear of the drift. The central portion 

 of the drift followed a right-line course, 

 in close agreement with the direction of 

 the air current, until a perpendicular 

 obstacle was interposed. Here the drift 

 divided into two streams, each flowing 

 with the same velocity, but having half 

 the cross-section. 



This experimental system of currents 

 finds its counterpart in nature. Under 

 the northeast trades in the north At- 

 lantic and the southeast trades in the 

 south Atlantic, we find a broad cen- 

 tral drift directed toward the shores of 

 America, the drift from the southeast 

 trades extending well into the Northern 

 Hemisphere, the two uniting some dis- 

 tance off Cape San Roque. To the 

 right and to the left of each of these 

 drifts the water fringes off, the direc- 

 tion of the motion is reversed, and the 

 so-called compensating currents mani- 

 fest themselves. Along the equatorial 

 margin of the two main drifts, under 

 the equatorial belt of calms, these com- 

 pensating currents unite to form the 

 counter-equatorial current, or Guinea 

 current, reaching a maximum intensity 

 during June, July, and August, the 

 months of the southwest monsoon. On 

 , the polar margin they either return 

 into the drift or are taken up by the 

 general easterly drift of the higher 

 latitudes. 



In the equatorial region of the earth 

 we thus have in either ocean three cur- 

 rents. In the north Atlantic the north 



equatorial current, due to the northeast 

 trades ; in the south Atlantic the south 

 equatorial current, due to the southeast 

 trades ; between these two the counter- 

 equatorial current, flowing at all times, 

 but reaching a maximum intensit) 7 and 

 covering a maximum area at the time 

 of the southwest monsoon. These first 

 two are westbound, carrying the water 

 toward the shores of America ; the 

 third is eastbound, carrying toward the 

 shores of Africa. They all suffer a 

 slight displacement with the season, in 

 harmony with the movements of the 

 trades, which oscillate slightly in lati- 

 tude with the movement of the sun in 

 declination. Also, in harmony with the 

 fact that the meteorological equator lies 

 slightly to the north of the geographical 

 equator, the south equatorial current 

 extends at all seasons well over into the 

 northern hemisphere. Corresponding 

 again with the fact that the southeast 

 trades exhibit greater constancy and 

 strength than the northeast, the south 

 equatorial current shows higher velocity 

 than the north, the average for the latter 

 amounting to but 13 miles in 24 hours, 

 for the former to 27 miles in 24 hours. 



Similar statements hold for the Pacific 

 Ocean. But from this point let us limit 

 ourselves to the Atlantic, the currents 

 for which are not only better known, 

 but also probably better developed, being 

 confined to a less extensive area than the 

 Pacific. 



In the Atlantic Ocean, then, the two 

 drifts unite some distance off Cape San 

 Roque, the eastern extremity of South 

 America. A portion of the water is- 

 diverted to the southward, forming the 

 Brazilian current ; the main body flows 

 west-northwest along the coast of South 

 America, some entering the Caribbean 

 Sea by way of the passages separating 

 the Windward Islands, the drift through 

 these passages often attaining a veloc- 

 ity of 50 miles a da}-. The remainder 

 passes to the northward of the islands, 

 forming the Bahama current. In this 



