158 A TEXTBOOK OF OCEANOGRAPHY 



The Origin of the Florida Current. According to 

 Franklin, the trade winds force the oceanic water into the 

 Caribbean Sea, and as a result the water is forced out through 

 the Florida Channel into the Atlantic. This theory holds the 

 Florida Current to be purely a drift current. The whole of 

 the Caribbean Sea has a strong westerly drift, and this water 

 must pass out through the Florida Channel, since the Gulf of 

 Mexico is a closed area. 



Another theory is that the Florida Current is due primarily 

 to the differences in density between the Gulf of Mexico and 

 the neighbouring ocean. As a whole, the waters of the Gulf 

 are colder than those of the ocean, and on this ground the level 

 in the Gulf should be lower. The salinity in the Gulf is 

 approximately 35 per mille, which is less than that of the 

 Florida Current. The level of the Gulf on a Galveston-Vera 

 Cruz section can be calculated to be 65 centimetres lower than 

 that of the Yucatan Channel. By similar reckoning the level 

 between the Yucatan Channel and the Florida Channel north 

 of Havana on the Bernini Keys section is approximately 

 identical. 



In winter strong westerly and north-westerly winds prevail 

 over the whole oceanic area between the New England coast 

 and the Azores. These winds are a cause of a depression in 

 the ocean level north of 30 N. Lat., and this is also a con- 

 tributory cause in the origin of the Florida Current. In 

 summer between Halifax and the Bermudas the prevailing 

 winds are from south and south-west, and these, again, help 

 the Florida Current. 



On its left hand the current is bounded by the " cold wall," 

 which is sharply marked off, its surface temperatures being 

 from 10 to 15 or even 20 C. below those of the Florida 

 Current. On its right hand the current's boundary is by no 

 means sharply marked off. 



Farther west in the Atlantic the Florida Current has several 

 main branches. The Antilles Current furnishes it with an 

 important constituent, and its common branches take several 



