CLIMATES OF THE OCEAN. 307 



887. Now, continuing for a moment our examination of Plate 

 lY., we are struck with the fact that most of the thermal lines there 

 drawn run from the western side of the Atlantic toward the east- 

 ern, in a northeastwardly direction, and that, as they approach the 

 shores of this ocean on the east, they again turn down for lower 

 latitudes and warmer climates. This feature in them indicates, 

 more surely than any direct observations upon the currents can 

 do, the presence, along the African shores in the North Atlantic, 

 of a large volume of cooler waters. These are the waters which, 

 having been first heated up in the caldron (§866) of St. Roque, in 

 the Caribbean Sea, and Gulf of Mexico, have been made to run 

 to the north, charged with heat and electricity to temper and reg- 

 ulate climates there. Having performed their offices, they have 

 cooled down ; but, obedient still to the " Mighty Voice" which the 

 winds and the waves obey, they now return by this channel along 

 the African shore to be again replenished with warmth, and to 

 keep up the system of beneficent and wholesome circulation de- 

 signed for the ocean. 



U 



