THE GULF STREAM. 253 
The earlier work of the Coast Survey in its investigations 
into the structure of the Gulf Stream (1845 to 1860) consisted 
in making sections across the stream, from the Straits of Bemini 
as far north as the latitude of Nantucket. From the studies of 
Craven, Maffitt, Bache, and Davis were developed the so-called 
cold and warm 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 warmer northerly currents. These alternating belts 
had no definite position, the size of the colder bands and warmer 
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.' 
! Great as is undoubtedly the effect of creasing the temperature of the water in 
the Gulf Stream proper (Fig. 175) in in- northern latitudes subject to its influence, 
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