380 THE DEPTHS OF THE SEA. [chap. viii. 



wards to the eastward of the AVest Indian Islands. 

 I am myself inclined, without hesitation, to regard 

 this stream as simply the reflux of the equatorial 

 current, added to no doubt during its north-easterly 

 course, by the surface-drift of the anti-trades which 

 follows in the main the same direction. 



The scope and limit of the Gulf- stream will be 

 better understood if we inquire in the first place into 

 its origin and cause. As is well known, — in two 

 bands, one to the north and the other to the south 

 of the equator, — the north-east and south-east trade- 

 winds, reduced to meridional directions by the east- 

 ward frictional impulse of the earth's rotation, drive 

 before them a magnificent surface current of hot 

 water 4,000 miles long by 450 miles broad at an 

 average rate of thirty miles a day. Off the coast of 

 Africa near its starting-point to the south of the 

 Islands of St. Thomas and Anna Bon, this ' Equa- 

 torial Current ' has a speed of forty miles in the 

 twenty-four hours, and a temperature of 23° C. 



Increasing quickly in bulk, and spreading out 

 more and more on both sides of the equator, it flows 

 rapidly due west towards the coast of South America. 

 At the eastern point of South America, Cape St. 

 Eoque, the equatorial current splits into two, and 

 one portion trends southwards to deflect the isotherms 

 of 21°, 15 0, 5, 10°, and 4 '5 C. into loops upon our maps, 

 thus carrying a scrap of comfort to the Falkland 

 Islands and Cape Hoorn ; while the northern portion 

 follows the north-east coast of South America, gaining 

 continually in temperature under the influence of the 

 tropical sun. Its speed has now increased to sixty- 

 eight miles in twenty-four hours, and by the union 



