70 THE OCEAN. 



tlie south-west winds,* on the climate of western Europe. While 

 rotating in the Gulf of Mexico, as in an immense cauldron, the 

 waters of the current are gradually heated ; when they escape through 

 the strait of Bcmini to enter the ocean, their temperature is not less 

 than 86"" Fahr., and exceeds by about 4° Fahr. the natural heat of 

 the neighbouring beds of water. The waters of the Gulf-streara lose 

 their warmth but slowly, and during winter tho}^ often have, off Cape 

 Ilatteras and the bank of Newfoundland, a temperature exceeding 

 by 2V or 28" Fahr. that of the rest of the Atlantic under the same 

 latitudes. When the Gulf- stream meets the polar current, the 

 former has still a temperature of 3G' or even 45° Fahr., whilst, even 

 at a distance of some hundreds of miles from the coasts of Labrador, 

 the latter is sometimes found to be below freezing-point (24*8 

 Fahr.) ; thus, in defiance of latitude, the waters of the tropics and 

 of the icy zone are brought into juxtaposition. In its advance to- 

 wards the north, the upper strata, which in consequence of radiation 

 have become colder than the subjacent layers, descend to a greater or 

 less depth in the mass of the current, and are replaced by the warmer 

 and lighter water, lying immediately below. Thus a constant alter- 

 nation of position is produced in the liquid strata of the Gulf-stream, 

 and one may remark in consequence, in crossing the whole breadth of 

 the current, a series of parallel bands of unequal temperature. f In 

 each of these bands the warm water rises by turns to the chilled sur- 

 face of the sea. It is a remarkable fact that if the Gulf-stream did 

 not flow as it does in a bed entirely composed of cold water, but moved 

 along the very bottom of the ocean, it would rapidly lose its high 

 temperature, and would cease in consequence to be a source of heat 

 for western Europe. In fact, the earth being a better conductor of 

 heat than the water, the warm waters of the current would communi- 

 cate their temperature to it, and would finally lose their whole store. 

 Eut the cold waters of the polar current, being interposed between 

 the bottom of the sea and the waters of the Gulf-stream, serve as a 

 protecting screen to the latter and hinder their refrigeration. It is by 

 such contrasts as these that the harmony of the world is established. 

 The quantity of heat which the Gulf-stream carries towards the 

 northern regions forms a very considerable part of the caloric stored up 

 in its waters under the tropics. The cetaceans, fish, and other inhabit- 

 ants of the torrid zone follow the course of the Gulf-stream without 



* See the chapter entitled, Climates. 

 t Franklin Bache, United States Coast -Survey/. 



