8 Historical Introduction 



salinities are immiscible, and his suggestion that there is a kind of peri- 

 staltic driving force acting upon the Gulf Stream. Maury says that the 

 difference of density at the poles and the equator must produce the ocean 

 currents, but he had no quantitative idea about how sahnity and tem- 

 perature are related to density. Accurate hydrographic tables had not 

 yet been constructed, and the salinity distribution in the sea was only 

 imperfectly known. 



The encouragement which Maury gave to the collection of ships' data, 

 however, his calling of the Maritime Conference at Brussels in 1853, and his 

 dissemination of hydrographic information, in the form of good pilot charts 

 and revised saiUng directions, were of great practical and commercial 

 importance. 



Modern surveying of the Gulf Stream began in 1844 with the work done 

 by the United States Coast and Geodetic Survey under the direction 

 of FrankHn's great-grandson, A. D. Bache (1860): fourteen temperature 

 sections between Tortugas and Nantucket. These early survey cruises 

 confirmed the existence of cold veins within the Stream. Bache supposed 

 that the cold veins were a result of the bottom configuration which diverted 

 the Gulf Stream in separate bands — irregularities which are now regarded 

 not as straight bands, but as meanders. In Bache 's time the 'bands' of 

 cold water were supposed to be invariable in number and position, and the 

 USCGS Gulf Stream Chart of 1860 shows them so. The currents were 

 observed only at the surface by the drift of the ship. 



During the Civil War there was a lull in Gulf Stream investigations, but 

 by 1867 they were resumed by Henry Mitchell, who attempted to measure 

 subsurface currents by means of two floats attached by a fine mre, one 

 of which remained at the surface while the other sank slowly. Mitchell 

 concluded that the velocity of the Gulf Stream off Fort Chorrera, Cuba, 

 extended undiminished to a depth of at least 600 fathoms. For the next 

 ten years the Bibb, the Bache, and the Blake continued to survey the 

 Stream. Early soundings had been made by rope, but in 1881 Bartlett 

 made use of the Thomson sounding machine, in which piano wire was 

 used. Bartlett did not detect the cold and warm bands showii on Bache's 

 chart. According to the modern view of the temporary nature of cold 

 inclusions in the Gulf Stream, this is not surprising. The Challenger, on her 

 world-Avide cruise, visited the Gulf Stream in 1873. 



John Elhott PUlsbury (1891) commanded the Blake during a remarkable 

 series of observations beginning in 1885. The ship was anchored along 

 several cross sections in the Florida Straits, and the current vector and the 

 temperature at various depths were determined. The anchoring gear and 

 the current meter were of Pillsbury's own design. Pillsbury went about his 

 task in a careful and painstaking manner. For example, he took two years 



