OCEAN 



4334 



OCEAN 



it contracts and becomes heavier until it reaches 

 the temperature 39 F. Sea water freezes at 

 28 F. A large number of records of the tem- 

 perature of the ocean at different depths proves 

 conclusively that the influence of the sun's rays 

 does not extend much below 1,000 feet; at 

 greater depth the temperature is practically 

 uniform. In the general system of ocean cur- 

 rents the warm water on the surface moves 

 from the equatorial towards the polar regions, 

 where it is cooled to the freezing point. This 

 cold water then settles towards the bottom and 



Currents flowing towards the equator are 

 flowing into regions whose eastward velocity is 

 greater than that of the regions they leave, and 

 they are crowded against the eastern coasts 

 of the continents, like the Labrador Current. 

 Moreover, since these are deep-sea currents, 

 their direction in certain localities may be 

 slightly changed by the shape of the ocean bed. 

 The influence of tides and coast line is local 

 and needs no consideration here. 



As the surface currents approach the polar 

 regions they are cooled, and the water finally 



i0 



180 



120 



60 







60 



PRINCIPAL OCEAN CURRENTS OF THE WORLD 



(1) Gulf Stream; (2) Canary Current; (3) Equatorial Current; (4) Benguela Current; (5) 

 Brazilian Current; (6) Japan Stream; (7) California Current; (8) Peruvian Current; (9) Mon- 

 soon Current; (10) Mozambique Current; (11) Australian Current. 



moves again towards the equator. Hence in 

 every ocean, except possibly the Indian, there 

 is a deep-sea, cold current moving slowly to- 

 wards the equator, and warm surface currents 

 moving towards the poles. 



Were it not for the rotation of the earth, 

 these currents would move directly north and 

 south. At the equator the rate of rotation is a 

 little over 1,000 miles an hour; at the poles it 

 is nothing. Currents flowing towards the poles 

 are flowing into regions whose velocity of rota- 

 tion is less than that of the regions they have 

 left, consequently their velocity eastward is 

 greater than that of the surrounding water, and 

 they flow towards the northeast, as in the case 

 of the Gulf Stream. Winds also exert a strong 

 influence upon these surface currents, and in all 

 the oceans their direction is approximately the 

 same as that of the prevailing winds. 



settles to the bottom and begins to journey to- 

 wards the equator. As it approaches the trop- 

 ics it becomes warm and rises to the surface to' 

 replace that evaporated by the great heat of 

 the sun in these regions. 



Currents of the North Atlantic. North of the 

 equator the trade winds (which see) drive a 

 current westward, forming the North Equato- 

 rial Current; when this current reaches the 

 West Indies it divides, a part of it entering the 

 Caribbean Sea and the other part bending 

 northward and joining the Gulf Stream, which 

 issues from the Gulf of Mexico and follows the 

 coast northward to Cape Hatteras, when it 

 turns eastward and spreads out until it becomes 

 a fan-shaped drift carrying warm water and 

 winds to the coast of Europe and greatly mod- 

 erating the climate of the northern part of that 

 continent. One branch passes along the coast 



