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 
oceanie 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 
Atlantie 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, 503°; 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 13° 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 Passage. 
The temperature sections across the Gulf of Mexico show, on 
the whole, 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 showing 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 
