380 THE DEPTHS OF THE SEA. [CHAP. VIII. 
wards to the eastward of the West 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. 
Roque, the equatorial current splits into two, and 
one portion trends southwards to deflect the isotherms 
of 21°, 15°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 
