428 APPENDIX V 



temperature is 12° C, the water almost invariably has a salinity 

 very near 35 per mille. This water at 12° C, with a salinity of 

 35 per mille, is found in the western part of the area (in the 

 Brazil Current) at a depth of 500 to 600 metres, but in the 

 eastern part (in the Benguela Current) no deeper than 200 to 250 

 metres (109 to 136 fathoms). 



We see further in both sections, and especially in the southern 

 one, that the isotherms and isohalins often have an undulating 

 course, since the conditions at one station may be different from 

 those at the neighbouring stations. To point to one or two 

 examples: at Station 19 the water a few hundred metres dowTi 

 was comparatively warm; it was, for instance, 12° C. at about 

 470 metres (256 fathoms) at this station; while the same tempera- 

 ture was found at about 340 metres (185 fathoms) at both the 

 neighbouring stations, 18 and 20. At Station 2 it was relatively 

 cold, as cold as it was a few hundred metres deeper down at 

 Stations 1 and 3. 



These undulating curves of the isotherms and isohalins are 

 familiar to us in the Norwegian Sea, where they have been shown 

 in most sections taken in recent years. They may be explained in 

 more than one way. They may be due to actual waves, which are 

 transmitted through the central waters of the sea. Many things 

 go to show that such waves may actually occur far below the 

 surface, in which case they must attain great dimensions; they 

 must, indeed, be more than 100 metres high at times, and yet- 

 fortunately — they are not felt on the surface. In the Norwegian 

 Sea we have frequently found these wave-like rises and falls. Or 

 the curves may be due to differences in the rapidity and direction 

 of the currents. Here the earth's rotation comes into play, since, 

 as mentioned above, it causes zones of water to be depressed on one 

 side and raised on the other; and the degree of force with which 

 this takes place is dependent on the rapidity of the current and on 

 the geographical latitude. The effect is slight in the tropics, but 

 ^reat in high latitudes. This, so far as it goes, agrees with the 



