NATURE OF THE STREAM 127 



results and the theories he deduced were included in his 

 Physical Geography of the Sea^ one of the first important 

 hydrographic books to be published. With this as a stimulus 

 and a starting point, the navigators, oceanographers, and 

 meteorologists who studied the Ocean River were now inter- 

 ested not merely in its general features but in its detailed 

 structure and its fluctuations in speed and position. 



Benjamin Franklin was responsible for one of the first sum- 

 maries of navigational knowledge to be published as a chart of 

 the Gulf Stream, and his grandson, Professor Alexander Dallas 

 Bache, was the first to carry out its systematic exploration. 

 When Professor Bache became director of the U. S. Coast 

 and Geodetic Survey he immediately drew up a detailed plan 

 to plot the position of the current and its boundaries, to find 

 out how permanent they are, and also to discover to what 

 depths the current penetrates and how the water temperature 

 changes at various depths. 



The brig Washington was commissioned in 1845 for this 

 work, but tragedy soon interrupted the investigations. The 

 vessel was small, and during the second year of operation the 

 commander and ten of the crew were lost overboard in a storm 

 off the North Carolina coast. In spite of the great difficulties 

 of the venture, a very large number of observations were made 

 aboard this and other vessels. At the western edge of the 

 Stream a considerable drop of temperature was noticed, called 

 the "cold wall." 



Bache's investigations continued for six years. The only 

 method of measuring the currents was by observing the ship's 

 drift, and the methods used for measuring depth were not 

 satisfactory in deep water; but he succeeded in obtaining a 

 great number of observations of temperature. From these he 

 concluded that between Florida and New York the Gulf 

 Stream is not a uniformly simple flow but is divided into alter- 



