44 EXPLORATIONS, WESTERN ATLANTIC, STEAMER BACHE, 1914. 



interesting discovery made by the Bache, for it shows that the 

 salinity of the water which flows into the Caribbean Sea through the 

 bottom of the Windward Passage (between Cuba and Haiti), the 

 Anegada Passage (between Sombrero and the Virgin Islands), and 

 possibly the passages between Dominica, Martinique, St. Lucia, and 

 St. Vincent, and thence into the Gulf of Mexico via the bottom of 

 the Yucatan Channel, is unaltered during its sojourn there, a gen- 

 eralization which also holds for temperature, as pointed out by A. 

 Agassiz (1888, p. 220). 



The vertical distribution of temperature in the upper layers on 

 the southern half of the Key West-Habana line is generally similar 

 to that of the southwestern part of the Gulf and Straits of Yucatan. 

 In spite of the interval of 40 years between the two sets of observa- 

 tions, the temperature at Bache station 10021 agrees almost exactly, 

 down to 800 meters, with the temperatiu'^ encountered by the Blake 

 on May 17, 1876, about 95 miles northwest of Habana, except for 

 being cooler at the immediate surface, a difference to be expected 

 because of the different seasons. And the slightly cooler water off 

 Habana (station 10199) was almost exactly identical with the tem- 

 peratm^es taken by the Blake in 1878 on the east side of the Yucatan 

 Channel close to Cape San Antonio, except, as before, for a seasonal 

 difference on the immediate surface. 



The much colder and fresher water off Key West must have a 

 twofold origin. Probably it comes chiefly from the current which 

 flows around the northern and eastern sides of the Gulf, following 

 the 200-meter curve (British Admiralty, 1897; Soley, 1911). This 

 current is considerably colder at all depths down to about 800 meters 

 than the water in the central and southern parts of the Gulf, as 

 shown by temperatures taken off Apalachicola, Fla., by the United 

 States Fish Commission steamer Albatross^ on March 13,^1885, 

 receiving its low temperature from the cold water in the north- 

 western part of the Gulf (Kriimmel, 1907). The water is even 

 colder on the surface at this season along the north shore of the 

 Gulf than in the Straits. However, this cold surface is confined to a 

 very narrow belt (Deutsche Seewalirte, 1882) and is probably due to 

 the cold '^northers" which blow so often in winter. 



The fact that, except for this shallow surface layer, the water was 

 considerably colder close to Key West than the Albatross found it 

 in the northern part of the Gulf (fig. 26), indicates that some up- 

 weUing was taking place from the deeps of the Gidf . Thus, tempera- 

 tures suggest that the west end of the Straits is a condensed epitome 

 of the Gulf as a whole, water from the north flowing around the 

 Florida cays, from the center of the Guff into the center of the 



a Dredging and other records of the United States Fish Commission stesLmer Albatross, etc.; Townsend, 

 C. H.; Report United States Commission of Fish and Fisheries, 1900, p, 494. 



