424 APPENDIX V 



is an effect of the earth's rotation, for the high temperatures mean 

 as a rule that the water is comparatively light, and the low that it 

 is comparatively heavy. Now, the effect of the earth's rotation in 

 the southern hemisphere is that the light (warm) water from above 

 is forced somewhat down on the left-hand side of the current, and 

 that the heavy (cold) water from below is raised somewhat. In 

 the northern hemisphere the contrary is the case. This explains 

 the cold water at a depth of 400 metres on the Equator; it also 

 explains the fact that the water immediately off the coasts of 

 Africa and South America is considerably colder than farther out 

 in the ocean. We now have data for studying the relation be- 

 tween the currents and the distribution of warmth in the volumes 

 of water in a way which affords valuable information as to the 

 movements themselves. The material collected by the Fram will 

 doubtless be of considerable importance in this way when it has 

 been finally worked out. 



Below 400 metres (218 fathoms) the temperature further 

 decreases everywhere in the South Atlantic, at first rapidly to a 

 depth between 500 and 1,000 metres (272 '5 and 545 fathoms), 

 afterwards very slowly. It is possible, however, that at the 

 greatest depths it rises a little again, but this will only be a 

 question of hundredths, or, in any case, very few tenths of a 

 degree. 



It is known from previous investigations in the South Atlantic, 

 that the waters at the greatest depths, several thousand metres 

 below the surface, have a temperature of between 0° and 3° C. 

 Along the whole Atlantic, from the extreme north (near Iceland) 

 to the extreme south, there runs a ridge about half-way between 

 Europe and Africa on the one side, and the two American conti- 

 nents on the other. A little to the north of the Equator there is 

 a slight elevation across the ocean floor between South America 

 and Africa. Farther south (between lats. 25° and 35° S.) another 

 irregular ridge runs across between these continents. We 

 therefore have four deep regions in the South Atlantic, two on the 



