THE GULF STREAM. 



253 



The earlier work of the Coast Survey iu its investigations 

 into the structure of the Gulf Stream (1845 to 1860) consisted 

 in making sections across the stream, from the Straits of Bernini 

 as far north as the latitude of Nantucket. From the studies of 

 Craven, Maffitt, Bache, and Davis were developed the so-called 

 cold and w arm bands, believed at that time to be the principal 

 characteristic of the Gulf Stream. The accompanying map 

 (Fig. 174), published in 1860 by the Coast Survey, will serve 

 to illustrate the structure of the GuLf Stream as it was then 

 understood ; namely, as a succession of belts composed of warm 

 northerly currents flowing side by side with a cold southerly 

 current, or of a cold southerly current which had found its way 

 under the Avarmer northerly currents. These alternating belts 

 had no definite position, the size of the colder bands and w^armer 

 belts being dependent, the one upon the force of the arctic cur- 

 rent, the other upon that of the tropical current, increased in 

 breadth and volume beyond the Bahamas by the whole of the 

 warm belt of surface equatorial water, which is deflected north- 

 ward by the Windward Islands, instead of forcing its way 

 through the passage between the Windward Islands, the Mona 

 and Windward Passages, and the Old Bahama Passage.^ 



1 Great as is undoubtedly the effect of creasing the temperature of the water in 

 the Gidf Stream proper (Fig. 175) in in- northern latitudes subject to its influence, 



Fig. 175. (Challenger.) 



