Prof. W. Thomson on the Depths of the Sea. 123 



with three registering thermometers, in 510 fathoms, in lat. 

 60° 45' N. and long. 4° 19' W., when the three thermometers, 

 whicli were within about 2° of one another, gave a mean result 

 of 32°'2, almost exactly the freezing-point of fresh water, and 

 more than 7° helow the " permanent point." Many subsequent 

 observations enabled us to determine that a cold area, where 

 the thermometer ranged about 32° F., at a depth of from 400 

 to 500 fathoms, extended between lat. 60° and 61° N., and 

 long. 4° 30' and 7° 30' W., and that an area stretched north- 

 Avestward, westward, and south-westward of this cold area, in 

 which the thermometer, to the depth of 650 fathoms, was very 

 permanent at 47*°5 to 49° F. This is an unexpected result, 

 but it is undoubtedly in the main correct. The soundings 

 were made with the greatest care and Avith the best instru- 

 ments, and several thermometers by different makers were 

 employed on every occasion, eveiy precaution being taken to 

 avoid error. 



Since the Gulf-stream, to which we attribute the warmth of 

 the warm area, appears to affect the temperature of the sea to 

 the very bottom, it is easy enough to conceive that the tem- 

 perature may be permanent over a considerable region at 49°; 

 but it is not so evident why the temperature of the cold area 

 should remain permanently two or three degrees above the 

 freezing-point of salt water. Experiments are yet wanting to 

 determine the influence of great pressure upon the freezing- 

 point of water ; but it is possible that the freezing-point may 

 be the actual limit, and that the Sixes thermometers, which 

 have large bulbs, register a degree or two too high, imder the 

 enoi-mous pressure of 100 atmospheres. If this be the case, 

 the condition of things must be very peculiar. Minute spi- 

 cules of light fresh ice must be continually forming, and rush- 

 ing upwards to be melted in the first shell of water whose 

 temperature is above the freezing-point. The animal inhabi- 

 tants must live in perpetual winter — a winter not more severe, 

 however, than that which is bravely borne by the myriads of 

 Limacinas and Clios which sport in every crack in the ice- 

 fields of the Arctic Sea. 



Nutrition. — The question of the mode of nutrition and life 

 of animals at these great depths is a veiy singular one. The 

 practical distinction between plants and animals is that plants 

 prepare the food of animals by decomposing certain inorganic 

 substances which animals cannot use as food, and rccombining 

 their elements into organic compounds upon which animals 

 can feed. This process, however, is constantly effected under 

 the influence of light ; there is little or no light in the depths, 

 and naturally there arc no plants. But the bottom of the sea 

 is a mass of animal life ; on what do these animals feed ? 



