292 SIEGE OF THE SOUTH POLE 
the British expedition having sailed over what was rep- 
sented as land in Wilkes’s map, obtained premature cur- 
rency with unfortunate results. 
The approach of the southern summer at length made 
it possible to return to Antarctic waters. Live stock and 
fresh provisions of all kinds had been taken on board 
until the deck looked like a farmyard, and on November 
23rd, 1841, the Erebus and Terror sailed from the Bay 
of Islands, accompanied for a few hours by H. M. S. 
Favourite, Commander Sulivan, who was stationed there. 
1 he weather proved fine and good progress was made to 
the southeastward, the object being to endeavour to find 
a way to the ice-barrier beyond the farthest point reached 
on the previous trip. Much time was spent on the way 
in ascertaining the temperature of the sea at great depths 
in order to find the point at which the temperature was 
uniform from surface to bottom. It was believed that 
along a certain line in the Southern Ocean an invariable 
temperature of 39.5 0 F. was maintained from surface to 
bottom all the year round; to the north of this line the 
surface water was warmer, and to the south of it the 
surface water was colder than the great mass of water 
below. Ross located this circle of uniform temperature 
in 55 ° 18' S. on December 13th; but the thermometers 
with which he was provided were probably not ade- 
quately protected against the excessive pressure which 
prevails at great depths, and consequently the results 
were not to be trusted. There is, as a matter of fact, no 
part of the open ocean either in the south temperate or 
even in the tropical zone where water so warm as 39.5 0 
F. is found at the bottom where the depth exceeds 1000 
fathoms. 
The weather grew cold and an intense fog set in, con- 
