TEMPERATUEES. 



221 



" Challenger " records 35.1°. These observations show, as we 

 approach the coast, an increase of temperature to a depth of 

 about 400 fathoms, and a diminution of temperature to a depth 

 of about 1,700 fathoms. 



In the section from Sombrero to Virgin Gorda (Fig. 144) 

 across the Anegada Channel, the temperatures agree more closely 

 with those of the Atlantic sections taken by the ^^ Challenger " 

 than with the more littoral one taken by the "Blake." There 

 is a marked increase of temperature in the layers between 

 100 and 300 fathoms. Between 400 and 600 fathoms, how- 

 ever, the water is somewhat colder, and at the bottom the tem- 



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Soinbrera 1.. 



Idartn arjsTA 



"Wrgia CoriaS. 



3j.i558 lm»< 



perature is nearly that of the corresponding 

 depth three hundred miles at sea. The bot- 

 tom temperature of this channel does not in- 

 dicate that the cold water is thrown up along 

 the gentler slope of the channel, as in the temperature sections 

 across the Yucatan Channel (Fig. 143), and across the narrow 

 part of the Straits of Florida. (Fig. 158.) .The bottom temper- 

 ature, 38° and 38i°, indicates that the basin and this channel are 

 an oceanic tongue of the Atlantic, and that there must be a ridge, 

 extending between Santa Cruz and Porto Rico, which separates 

 it from the Caribbean basin.^ Far inside of the Caribbean Sea, 



^ The temperature of 38^^ also shows 

 that the Anegada Channel is divided by 

 a ridge from the deeper part of the oce- 

 anic basin of the western Atlantic to 

 the north of the West Indies, as in that 

 basin the temperature observed by the 

 " Challenger " and by Lieutenant-Com- 



mander Brownson sinks to 36° in its deep- 

 est parts. Since this was written, the 

 U. S. Fish Commission steamer " Alba- 

 tross," Lieutenant-Commander Tanner, 

 has developed a ridge runnmg between 

 Santa Cruz and Porto Rico, with a great- 

 est depth of about 900 fathoms and a 



