300 THE DEPTHS OF THE SEA. [chap. vii. 



face is sometimes subjected to intense cold, warmer 

 water may be found below, until the balance is . 

 restored by convection. This I believe, however, to 

 be entirely exceptional ; and it may certainly be 

 taken as the rule for all latitudes that if we dis- 

 regard the film which is affected by diurnal altera- 

 tions, the temperature sinks from the surface to the 

 bottom. 



The first important series of deep-water tempera- 

 ture observations was made during the Arctic voyage 

 under Sir John Ross in the year 1818. On Sept. the 

 1st, lat. 73° 37' N., long. 77° 25' W., the temperature 

 at the surface being 1°*3 C, the registering thermo- 

 meter gave at eighty fathoms 0° 0., and at 250 

 fathoms— 1°-4 0. On the 6th of September, lat. 

 72° 23' N., long. 73° 07' W., the first serial sounding 

 on record was taken, the thermometer having been let 

 down to 500, 600, 700, 800, and 1,000 fathoms in 

 succession, the thermometer showing each time a 

 lower temperature and indicating at the greatest 

 depth named a temperature of — 3°-6 0. On the 

 19th of September, in lat. 66° 60' N., long. 60° 30' 

 W., another serial sounding was taken, the tempera- 

 ture being registered at 100 fathoms — 0°'9 C, at 

 200 -r-7 C, at 400 -2°-2 0., and at 660 fathoms 

 -3°-6 0. On the 4th of October, lat. 61° 41' N., 

 long. 62° 16' W., Sir John Ross sounded, but found 

 no ground in 950 fathoms ; at the same time the 

 self-registering thermometer was sent down, and the 

 temperature of the sea at that depth was found to 

 be 2° C, while at the surface it was 4° 0., and the air 

 at 2° 7 0. I am informed by General Sir Edward 

 Sabine, who accompanied Sir John Ross's expedition, 



