CHAP. II.] MADEIRA TO THE COAST OF BRAZIL. 75 



twenty to seventy miles a day, is, ronghly, the fourth degree of 

 north latitude — a little to the southward of this parallel toward 

 the coast of Africa, considerably to the northward, about 35° 

 W. longitude, where it approaches its bifurcation off Cape San 

 Roque. 



Occupying a band approximately between the parallels of 4° 

 and 8° N., there is a tolerably constant current to the eastward, 

 the equatorial counter -current, averaging, in the summer and 

 autumn months, when it attains its maximum, a rate of twenty 

 to forty miles a day. The causes of this current are not well 

 known ; it occupies a portion of the ever-varying space between 

 the north-east and the south-east trades, and it seems probable 

 that it may be a current induced in an opposite direction, in the 

 " zone of calms," by the rapid removal of surface-water to the 

 westward by the permanent easterly wind-belts. Opposite Cape 

 Yerde this easterly current takes a southward direction ; it is 

 joined by a portion of the southern reflux of the Gulf -stream ; 

 and, under the name of the " Guinea Current," courses along 

 the African coast as far south as the Bights of Benin and Bi- 

 afra, where it disappears. 



The Guinea or " African " Current is a stream of warm 

 water, averaging from 250 to 300 miles in width, with an av- 

 erage rate of from twenty to fifty miles a day. Its greatest 

 concentration and force are opposite Cape Palmas, where it is 

 jammed in by the northern edge of the equatorial current ; its 

 width is there reduced to a little over a hundred miles, and it 

 attains a maximum speed of one hundred miles a day. There 

 seems to be no doubt that this current must be regarded as a 

 continuation of, and as being almost entirely derived from, the 

 equatorial counter-current. It is evident that a great part of 

 the surface-water must have an equatorial origin, for when we 

 took our observations, nearly at the hottest time of the year, 

 the surface-temperature was equal to the mean maximum tem- 

 perature of the air, and one degree above its mean minimum 



