OCEAN CURRENTS. 



direction of the line westward, and passing among the islands of 

 the Indian Archipelago, it traverses the Indian ocean, and sweep- 

 ing round the Cape of Good Hope, turns northwards along the west 

 coast of Africa, until it encounters the shores of the Gulf of Guinea, 

 which again divert it westward, where it resumes the name of the 

 equatorial current. Traversing the Atlantic, it arrives at the 

 northern coast of South America, and enters the Caribhean Sea 

 through the chain of the West India islands, from which it arrives 

 in the Gulf of Mexico. 



205. Gulf stream. In this long course, after cooling the 

 waters of the tropical ocean, its own temperature is at length 

 raised to a high point, and in that thermal state it arrives in the 

 Gulf of Mexico. The direction of the current is there changed 

 by the southern coast of North America, and it issues through 

 the channel between Cuba and Florida, flowing northward along 

 the coast of the United States, and about the 35th degree of lati- 

 tude turning north-east, it again traverses the Atlantic, dividing 

 its course into two branches, one directed between the British Isles 

 and Iceland to Spitzbergen in the Arctic ocean, and the other by 

 the Azores and Madeira back to the coast of Morocco. 



At the point where it issues from the Gulf of Mexico, the 

 current takes the well-known denomination of the Gulf stream. 

 Its temperature, as just stated, is so elevated that its existence 

 can readily be determined by navigators by means of the ther- 

 mometer. It becomes thus a means of transporting to the regions 

 of the northern frigid zone a portion of the tropical heat, so as to 

 produce the equalising effect already mentioned. 



206. Course and limits of ocean currents evident. " The 

 currents of the ocean," observes Humboldt, " present a remarkable 

 spectacle, maintaining a nearly constant breadth. They cross the 

 sea in different directions, like rivers of which the adjacent 

 undisturbed masses of water form the banks. The line of 

 demarcation between the parts in motion, and those in repose, is 

 most strikingly shown in places where long bands of sea-weeds, 

 borne onward by the current, enable us to estimate its velocity. 

 Analogous phenomena are sometimes presented to our notice in 

 the lower strata of the atmosphere, when, after a violent storm, 

 the path of a limited aerial current may be traced through the 

 forest by long lanes of overthrown trees, whilst those on either 

 side remain unscathed." 



207. Ocean rich in animal life. Although the surface of the 

 ocean is less rich in animal and vegetable forms than that of 

 continents, yet when its depths are searched, perhaps no other 

 portion of our planet presents such fullness of organic life. 

 Charles Darwin, in the agreeable journal of his extensive voyages, 



191 



