300 THE DEPTHS OF THE SEA. [CHAP. vn. 



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 C., and at 250 

 fathoms -l-4 C. On the 6th of September, lat. 

 72 23' K, 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 C. On the 

 19th of September, in lat. 66 50' K, long. 60 30' 

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

 ture being registered at 100 fathoms 0'9 C., at 

 200 1-7 C, at 400 -2-2 C., and at 660 fathoms 

 -3-6 C. On the 4th of October, lat. 61 41' 

 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 0< 7 C. I am informed by General Sir Edward 

 Sabine, who accompanied Sir John Ross's expedition, 



