50 : The Atlantic 



streams bend westward and become again a part o£ the North Equa- 

 torial Current. So with the North Atlantic currents we have made a 

 complete right-hand or clockwise circuit of this portion of the Atlan- 

 tic, a circuit caused by the winds but complete, well defined, fully 

 organized. 



But the Florida Current that comes up between the Bahamas and 

 Florida and that Floridians and unregenerate mariners will no doubt 

 continue to call the Gulf Stream — where does that come from and 

 what gives the whole system its drive and power and direction? 



Let us return for a moment to mid-Atlantic in the center of the 

 North Equatorial Current. We are moving straight westward with 

 the current pushing us along and the northeast trades at our back. 

 Now the part of the current that is on our right swings away farther 

 to the right but soon additional water from the South Atlantic sweeps 

 in from the left and the whole stream, with the east winds still push- 

 ing, passes between the Lesser Antilles and on into the Caribbean. 

 Here, with the Central American coast blocking the way, the waters 

 of the current pile up. With increased speed they flow through the 

 only available exit, the narrow Yucatan Channel. Part of this stream 

 may make a circuit in the Gulf of Mexico, but the gulf also is contin- 

 ually receiving this large volume of wind-driven water so the greater 

 volume of all the flow that has come through the Yucatan Channel 

 swings quickly around the west end of Cuba and, still picking up 

 speed, rounds the end of Florida as the Florida Current: in other 

 words the start of that Gulf Stream system whose course we have 

 already traced. 



Though it may seem strange that there could be any appreciable 

 difference in "sea levels" or that so large a body of water as the Gulf 

 of Mexico could be affected in this way, it is in fact true that sea level 

 in the Gulf of Mexico is higher than sea level on the Atlantic coast. 

 By measurement sea level in the gulf at Cedar Keys, Florida, is nine- 

 teen cm. or about seven and one-half inches higher on the average 

 than sea level at St. Augustine, Florida. 



The current itself also accounts for a strange unevenness in sea 

 level. Owing to the rotation of the earth a current running like this 

 one will sort out light water from heavier water in its composition 

 and in the Northern Hemisphere the light water will slope up on 

 our right hand if we face in the direction toward which the current 

 is running. It has been calculated as a result that sea level on the 

 north coast of Cuba is forty-five cm. or almost eighteen inches higher 

 than sea level at Key West, Florida. 



