From Cape of Good Hope to Melbourne. 93 



an effectual barrier, a " cold wall," which arrests the further 

 progress southwards of the equatorial currents of the three great 

 oceanic basins. These warm currents — the Brazilian Current 

 in the South Atlantic, the Agulhas Current or Cape Current 

 of the Indian Ocean, and the currents which flow along the 

 east coast of Australia and of New Zealand — on meeting the 

 easterly current of the Southern Ocean, are split up into two, 

 or rather three portions : the first portion is bent round and 

 flows eastwards as a warm surface-current ; the second, mixing 

 with the cold current, is also carried eastwards, and accounts for 

 the rise of temperature — from 5° C. to 10° C. or 16° C. according 

 to the season — which is observed between lat. 50° and 40° S. ; 

 the third sinks below the cold surface-current, and, taking a 

 south-easterly course, flows as a warm under-current into the 

 Antarctic Ocean. These are the warm currents which under- 

 mine the enormous ice-masses that rise, under the name of the 

 " Ice-barrier," like a solid wall to a height of from 150 to 300 

 feet above the surface of the sea, and detach from them the 

 innumerable floating- icebergs which strew the face of the 

 Southern Ocean down to 50° and 40° latitude. The continual 

 melting of these icebergs between 60° and 40° latitude supplies 

 the masses of cold water which, to a depth of several thousand 

 fathoms, fill up the basins of the Atlantic, the Pacific, and the 

 Indian Ocean. 



This splitting-up of the currents assumes especially marked 

 features off the Cape of Good Hope. The Agulhas Current, 

 immediately after crossing the meridian of the Cape, flows 

 into the angle between the two branches of the Antarctic 

 Current, between which it is completely annihilated as a 

 surface-current, for few if any traces of it appear at the surface 

 further westward. At the time of the " Challenger's " visit 

 to these latitudes, the surface-temperatures between Tristan 

 d'Acunha and the Cape ranged from 12° C. to 15° C, while the 



