CHAP. VIL] DEEP-SEA TEMPERATURES. 301 



that these observations were made with registering 



o 



thermometers guarded somewhat in the same way 

 as those which we employed in the 'Porcupine.' 

 There is almost sufficient internal evidence that the 

 mode of protecting these thermometers must have 

 been satisfactory, for the temperatures at the greatest 

 depths are such as might have been expected from 

 Miller-Casella thermometers. Unguarded instru 

 ments would certainly have given higher indica 

 tions. 



The last of the observations quoted, a considerable 

 way up Davis' Strait, is of great interest. The tem 

 perature of the surface of the sea was nearly a 

 degree and a half Centigrade above that of the air, 

 and the temperature of the water was altogether 

 unusually high. It is now well known that at 

 certain seasons of the year a very marked extension 

 of the Gulf-stream passes into the mouth of the 

 Strait. The isotherms for September and July are 

 shown on the chart from data kindly procured for 

 me by Mr. Keith Johnston. 



Sir Edward Sabine, in an extract from his pri 

 vate Journal of Sir John Ross's voyage quoted by 

 Dr. Carpenter, 1 gives a lower temperature than any 

 hitherto recorded. He says : " Having sounded on 

 September 19th, 1818, in 750 fathoms, the regis 

 tering thermometer was sent down to 680 fathoms, 

 and on coming up the index of greatest cold was 

 at 25-75 Fahrenheit (-3'5 C.), never having known 

 it lower than 28 (-2'2 C.) in former instances, even 

 at a depth of 1,000 fathoms; and at other times 



1 Dr. Carpenter's Preliminary Report on Deep-Sea Dredgings. Pro 

 ceedings of the Royal Society of London, vol. xvii. p. 186. 



