EXPLORATIONS, WESTERN ATLANTIC. STEAMER BACHE, lOU. 43 



lines normal to the coast, from Cape Canaveral northward (Agassiz, 

 1888, fig. 176), shows that except on the immediate surface the Gulf 

 Stream retains its character as a cool current as far as Cape Fear, 

 beyond which it is indistinguishable from the water farther to the 

 east. Furthermore, the evidence of salinity is, if anything, even 

 more conclusive, because while the bottom water of the channel 

 (34.8-34.9Voo) is continuous with the abyssal water off Habana 

 at its west end and hence of the Gulf, off the Bahamas water of this 

 salinity was encountered only below 1,800 meters, a vertical drop 

 of 1,000 meters from the exit of the channel. Hence, to suppose 

 that the bottom water of the Straits enters from the Atlantic abyss, 

 we must assume a vertical upweUing of 1,000 meters, of which there 

 is no evidence whatever. And it can not be coastal water from the 

 north, because far too salt. In short, it is clear that the bottom 



Stations 



Meter 



Fig. 46.— Profile of density, at temperature in situ and corrected for pressure, across the Straits of Florida, 



Gun Cay to Cape Florida. 



current in the Straits must flow in the same direction as the surface 

 current — i. e., from the Gulf of Mexico — driving the heavy abyssal 

 water of the latter (1.03 + ) up the slope, thus producing the 

 density gradient mentioned above. This bottom current must be 

 constant, or nearly so, since the rise of cold comparatively fresh 

 water from the deeps of the Gulf up the rising floor of the Straits to 

 near the siu^ace at its exit is now shown to be a permanent phe- 

 nomenon. In short, the countercurrents occasionally^ detected by 

 Pillsbury on the bottom on the Florida side of the channel at about 

 100 fathoms, like the surface countercurrents so long recognized by 

 mariners, are merely local reaction phenomena, or eddies. How- 

 ever, the velocity of the bottom current is certainly only a fraction 

 of the surface drift; and it may be very small indeed. 



The close agreement between the salinity of the bottom of the 

 Straits and that of the water in the Atlantic abyss is not the least 



