THE CURRENTS OF THE ATLANTIC. 383 



lucifer match will take fire, if it chance to fall on the arid and 

 heated soil. 



You see then that, owing to the diversity in the physical 

 characters of the earth's crust, the heat developed is hy no means 

 proportionate to the intensity of the solar action. But there is 

 another, and a powerful cause, which tends to distribute the heat 

 actually imparted, and to render it more uniform. The air ahove 

 the Equatorial regions of the earth ascends, and flows over towards 

 the Poles ; while the colder air of the Polar regions flows beneath 

 in the opposite direction to take its place. In this manner a 

 double system of aerial currents is established, which tends to 

 mitigate the extremes of heat and cold on the earth's surface, and 

 to reduce the differences which would otherwise exist. 



And a similar interchange 'of temperatures is effected by means 

 of the waters which cover so large a portion of the earth's surface. 

 The Oceanic currents, like great arteries, distribute to the more 

 remote portions of the globe the vast store of heat which it 

 receives from the sun in the intertropical regions. To one of 

 these I wish to invite your attention more particularly, because it 

 is to it, mainly, that the peculiarities of our own climate are owing. 

 Let us trace it from its source. 



In the Atlantic Ocean, within the Tropics, the waters flow 

 from east to west in a majestic stream, whose breadth occupies 

 30 of latitude. It is known under the name of the " Equatorial 

 current." This current breaks into two, or bifurcates, when it 

 encounters the projecting shoulder of the South American Continent 

 at the Cape St. Eoque ; the main portion sweeping along the 

 northern shore of the Continent, while another portion is deflected 

 to the southward, and follows the eastern shore. The former of 

 these is the parent of the " Gulf-Stream." Continuing its westerly 

 course, along the north coast of South America, it enters the 

 Caribbean Sea, and passes into the Gulf of Mexico through the 

 channel of Yucatan. It then makes the entire circuit of the gulf, 

 clinging to the shore of the North American Continent, until its 

 direction is changed from westerly to easterly ; and it passes out 

 of the gulf through the Straits of Florida, and issues into the 

 Atlantic. 



It is at this point that the current takes the name of the 

 4t Gulf-Stream." Its breadth is here upwards of 30 miles, and 

 its depth more than 2000 feet ; and it has a velocity of four miles 



