1462 



CRUSTACEA. 



of Fuegia sinks nearly to 35°, if not quite, and the line of 35° there- 

 fore runs very near Cape Horn, if not actually touching upon Fuegia. 



North Pacific Ocean. — Isocryme of 80° F. — The waters of the At- 

 lantic in the warmest regions, sink below 80° F. in the colder season, 

 and there is therefore no proper Supertorrid Region in that ocean. In 

 the Gulf of Mexico, where the heat rises at times to 85° F., it sinks 

 in other seasons to 74° and in some parts, even to 72° F. j and along 

 the Thermal equator across the ocean, the temperature is in some 

 portions of the year 78°, and in many places 74°. 



But in the Pacific, where the temperature of the waters rises in 

 some places to 88° F., there is a small region in which through all 

 seasons, the heat is never below 80°. It is a narrow area, extending 

 from 165° east to 148° west, and from 7i° north to 11° south. In 

 going from the Feejees in August, and crossing between the meridians 

 of 170° west and 180°, the temperature of the waters, according to 

 Captain Wilkes, increased from 79° to 84° F., the last temperature 

 being met with in latitude 5° south, longitude 175° west, and from 

 this, going northward, there was a slow decrease of temperature. 

 The Ship Relief, of the Expedition, in October, found nearly the same 

 temperature (83£°) in the same latitude and longitude 177° west.* 

 But the Peacock, in January and February {summer months), found 

 the sea-temperature 85° to 88° F., near Fakaafo, in latitude 10° south, 

 and longitude 171° west. In latitude 5° south and the same longi- 

 tude, on the 16th of January, the temperature was 84°; in 3° south, 

 January 10th, it was 83° F.; on March 26th, in 5° south, and longi- 

 tude 175° east, the temperature was 86° F.; on April 10th, in the 

 same longitude, under the equator, at the Kingsmills, the temperature 

 was 83£° F. ; on May 2d, at 5° north, longitude 174° east, 83i° F.; 

 May 5th, latitude 10°, longitude 169° east, 82° F. The fact that the 

 region of greatest heat in the Middle Pacific is south of the equator, 

 as it has been laid down by different authors, is thus evident; the 

 limits of a circumscribed region of hot waters in this part of the 

 Pacific, were first drawn out by Captain Wilkes. 



Another Supertorrid region may exist in the Indian Ocean, about 

 its northwestern portion; but we have not sufficient information for 

 laying down its limits. 



Isocryme of 74° F.— -At San Bias, on the coast of Mexico, Beechey 



* See, for these facts, Captain Wilkes's Report on the Meteorology of the Expedition. 



