230 THREE CRUISES OF THE "'• BLAKE." 



sponds on the Atlantic side to a depth of but little less than 

 300 fathoms ; but near the six-hundred-fathom line the tem- 

 peratures of the inside section again agree with those of the 

 oceanic section. 



Across the Yucatan Channel the temperature section shows 

 great similarity with the Atlantic section just outside of Som- 

 brero. The water which finds its way into the Gulf of Mexico 

 has nearly the same temperature as the water forced from the 

 Atlantic over the eastern edge of the Caribbean basin through 

 the passages between the Windward Islands. In the Gulf of 

 Mexico itself, the sections from the Tortugas to Yucatan show 

 a very decided increase of temperature below the one-hundred- 

 fathom line. At 200 fathoms, the temperature is 65° ; at 300 

 fathoms, it is 57° ; at 400 fathoms, 50^ ; at 500 fathoms, 41° ; 

 with a bottom temperature of 39° at 1,685 fathoms. That is, 

 the temperature of the water between 150 and 600 fathoms is 

 from lh° to 4° warmer than the water which finds its way into 

 the Gulf of Mexico. Compared with the temperature section of 

 the Windward Passage (Cuba to San Domingo), the temperature 

 of the Yucatan Channel line between 150 and 500 fathoms is 

 from 1° to 2° warmer than that of a similar belt of water in 

 the Windward Passasfe. 



The temperature sections across the Gulf of Mexico show, on 

 the Avhole, that the temperature of the upper strata between the 

 surface and 150 fathoms diminishes much more rapidly than in 

 the Caribbean, and that already at the one-hundred-fathom line 

 it is lower than at the same depth in the Caribbean. From the 

 one-hundred-fathom line the temperature falls very rapidly, the 

 sectional lines across the Gulf showino; a difference of 5° to 8° 

 between 150 and 600 fathoms from the temperatures of corre- 

 sponding depths in the Yucatan Channel. A comparison of 

 temperatures in the Gulf of Mexico on the two sides of the 

 Yucatan Bank brings out a striking contrast in temperature 

 between the eastern and western sides of the Gulf. 



The lines from the Tortugas to Yucatan (Fig. 154) have 

 as a whole a warmer section than that of the Straits of Yucatan, 

 while the lines from the Yucatan Bank to the coast of Mexico 

 show at the same depth an increase of cold of more than 10° at 



