186 



Dr. Carpenter's Preliminary Report [Dec. 17, 



area, where the depth was 500 fathoms [914 metres] and upwards; notwith- 

 standing that the ^r/«ce-temperature varied little from 52° [11°-1 Cent.], 

 alike in this region and in neighbouring areas of similar depth, iu which the 

 minimum temperature was only a few degrees beneath that of the surface. 

 The current doctrine in regard to deep-sea temperatures may be considered 

 to be that expressed by Sir J. Herschel (Physical Geography, 1861, p. 45) 

 in the following terms : — " In very deep water all over the globe a uniform 

 temperature of 39° Fahr. [4° Cent.] is found to prevail, while above the 

 level, when that temperature is first reached, the ocean may be considered 

 as divided into three great regions or zones — an equatorial and two polar. 

 In the former of these, warmer, in the latter colder, water is found at the 

 surface. The lines of demarcation are of coiirse the two isotherms of 39° 

 mean annual temperature." This doctrine, which is more fully and ex- 

 plicitly set forth by Dr. Wallich (' The North- Atlantic Sea-bed/ 1862, 

 pp. 98, 99), rests, I believe, chiefly on the temperature-observations made 

 in Sir James Ross's Antarctic Expedition, which were not inconsistent with 

 the prevalent belief that sea-water, like fresh water, has its maximum 

 density at this temperature, and that consequently water at 32° or 33° 

 cannot underlie water at 39°. Several instances, however, had been pre- 

 viously recorded, in which temperatures below 39° had been observed. Thus 

 Lieut. S. P. Lee, of the United States Coast Survey, in August 1847 found 

 37° below the Gulf-stream, at the depth of 1000 fathoms [1829 metres], in 

 lat. 35° 26' N. and long. 73° 12'W.; and Lieut. Dayman found the tempe- 

 rature at 1000 fathoms [1829 metres] in lat. 51° N. and long. 40° W. to 

 be 32° 7' [0°-4 Cent.], the surface- temperature being 54°-5 [12°-5 Cent.]*. 

 " At the very bottom of the Gulf-stream," says Lieut. Maury (Physical 

 Geography of the Sea, 1860, p. 58), " when its surface-temperature was 80° 

 [26°* 6 Cent.], the deep-sea thermometer of the Coast Survey has recorded a 

 temperature as low as 35° [l°-6 Cent.]. These cold waters doubtless come 

 down from the north to replace the warm waters sent through the Gulf- 

 stream to moderate the cold of Spitzbergen ; for within the Arctic Circle the 

 temperature at corresponding depths off the shores of that island is said to 

 be only one degree colder than in the Caribbean Sea, while on the shores of 

 Labrador and in the Polar Sea the temperature of the water beneath the 

 ice was invariably found by Lieut. De Haven at 28° [ — 2°'2 Cent.], or 4° 

 below the melting-point of freshwater ice. Capt. Scoresby relates that on 

 the coast of Greenland, in latitude 72°, the temperature of the air was 42° 

 [5°-5 Cent.], of the water 34° [1°-1 Cent.], and 29° [— 1°-6 Cent.] at the 

 depth of 118 fathoms "f. That there is no Physical improbability in the 



100 atmospheres to which their bulbs were subjected, would prevent them from record- 

 ing a minimum as low as the actual minimum ; and it seems to us not at all improbable 

 that the actual minimum may have been from 2° to 4° lower than the recorded 

 minimum. — In any renewal of the inquiry, it will be of course desirable that the 

 Thermometric apparatus used should be specially protected from this source of error. 



* See Purdy on the Northern Atlantic Ocean, 12th edit., 1865, pp. 330 and 338. 



t General Sabine has been kind enough to send me the following extract from his 



