NATURE OF THE STREAM 145 



During the past century the earher notion of a gradually 

 widening River in the ocean, with sharp boundaries and a 

 fixed course, has given way before accumulating evidence of 

 changes in position and speed. Operation Cabot brought these 

 ideas into focus and showed that the Gulf Stream is narrow 

 rather than wide, that it does not broaden out, and that a 

 sharp drop of temperature may not necessarily mean the 

 edge of the main current. When it leaves the confining influ- 

 ence of the land after passing Cape Hatteras it continues as 

 a jet stream, and behaves in some ways like the high-speed 

 jet streams that twist across the upper levels of the atmos- 

 phere. It begins to curve in wavy fashion from side to side 

 as it moves to the northeast, and the curves grow wider until 

 it looks like the leisurely meander of a slow river through flat 

 country. But the current itself is still little wider than when 

 it left the restraining banks of the Florida Straits, and it still 

 flows at a good pace. Because of its wavy course the general 

 easterly movement of water is slowed down; and we now 

 see why a vessel sailing through this region is unable to judge 

 the speed of the Gulf Stream from its accumulated effect on 

 dead reckoning. A vessel sailing to the east may at one time 

 be set almost to the southeast by a four-knot current, but a 

 few hours later it may again cross the River, which this time 

 might be running as fast to the north. 



There is nothing fixed about these waves and curves in the 

 Stream, for they may change their position as rapidly as eleven 

 miles in a day; and they seem to become increasingly great 

 until they reached the neighborhood of longitude 63° W. 

 At unknown intervals of time a loop may twist so far out of 

 line that it remains connected with the Stream only by a long 

 narrow neck of flowing water — which may finally become 

 completely pinched off. When this happens the loop becomes 

 a more or less circular cyclonic eddy, running off on its own 

 to the westward, an isolated swirl of Gulf Stream water. It 



