HALF AN HOUR WITH THE WAVES. 13 



soundings of the " Porcupine " showed the important 

 effects of these currents on marine life. It was 

 found that where Arctic or cold currents ran along 

 the ocean floor, notwithstanding that the upper 

 waters were warmer, that floor was occupied by 

 shell-fish similar to those living in the seas of the 

 north. This great Arctic current is being more 

 studied and better understood than formerly. What 

 is true regarding an interchange of warm and cold 

 waters in the northern hemisphere is equally so of 

 those in the southern. The cold waters of the 

 southern pole flow towards the equator in no fewer 

 than three great currents. One of these splits up 

 in forty-five degrees south latitude, sending one 

 arm round Cape Horn, and the other, which is 

 known as " Humboldt's Current," up the Chilian 

 and Peruvian coasts. The second great southerly 

 current runs towards Africa, getting divided by the 

 Cape of Good Hope, so as to be forced up the eastern 

 and western coasts. The hot water of the Indian 

 Ocean escapes southerly, and is replaced by the 

 third great current ; so that the warm waters of the 

 Indian Ocean circulate between Africa and Australia, 

 one branch of the current running along the 

 southern coast of the latter country. 



These currents tend considerably to render the 

 specific gravity of the sea-water tolerably equable, 

 by mixing them up. In this they are aided by tides 

 very considerably. For the ocean to maintain a 

 tolerably equal specific gravity is of great impor- 



