300 THE DEPTHS OF THE SEA. [CHAP. VIL. 
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 
Ist, 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° C., and at 250 
fathoms — 1°. 4C. 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 —38°6C. On the 
19th of September, in lat. 66° 50’ N., 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°6C.- 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° C., and the air 
at 2°"7 C. I am informed by General Sir Edward 
Sabine, who accompanied Sir John Ross’s expedition, 
