By studying a great number of current and 

 weattier observations made by merctiant ships, 

 Matthew Maury was able to work out the most 

 favorable routes for commercial ships to 

 follow during their crossing of the Atlantic. 

 This chart prepared by Maury shows the 

 quickest routes to and from Europe. 



simply by plotting careful observations. We have to find hw the 

 currents are generated. For the past 150 years the main question - 

 still not completely answered - has been : How do the winds and 

 differences of water density between one part of the ocean and 

 another conspire to cause surface and deep-water movements and 

 exchanges between them? FrankUn and Rennell were convinced 

 that the winds were the main cause of the surface currents. Rennell, 

 however, knew that when water is piled up against a coast by the 

 wind, there might be a "stream current" away from the area of 

 accumulation - not necessarily in the direction of the wind. 



Temperature measurements soon showed that there was very 

 cold water at the bottom of the tropical oceans. As early as 18 12 

 Alexander von Humboldt maintained that this was evidence of 

 bottom currents flowing from the polar regions toward the Equator. 

 Jean Arago, the French physicist, said that the inabiUty of the polar 

 bottom currents to get into the Mediterranean Sea would explain 

 why the temperature at the bottom of the Mediterranean was 

 higher than at the same level outside. (He knew about the relatively 

 warm undercurrent flowing out through the Strait of Gibraltar.) 

 Humboldt made a clear distinction between the general circulation 

 of the water in the ocean and the rapid surface currents that had 

 most bearing on navigation. 



Emil von Lenz, the German physicist who reviewed all the 

 evidence available up to 1845, said that a flow of warmer water 

 from the Equator to the poles must take place at the surface. 

 Further, this surface flow must be constantly supplied at the Equator 



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