OCEANIC CIRCULATION 117 



trade- winds upwelling is to be expected. The 

 North Atlantic is remarkable for its high 

 density at 100 fathoms — ^higher than that 

 observed in any other part of the ocean. In 

 the South Atlantic off the South American 

 coast the density is high, falling on proceeding 

 eastwards towards the mid-Atlantic ridge, 

 while still farther east density is much lower, 

 evidently in relation to the upwelling towards 

 the African coast. 



At a depth of 200 fathoms density is much 

 higher in the North than in the South Atlantic, 

 and higher in the South than in the North 

 Pacific, but in the Pacific the observations 

 approximate to each other from lat. 30° N. 

 to 40° S., the mean being much below that 

 of the North Atlantic. 



At a depth of 400 fathoms density is con- 

 siderably higher in the North than in the South 

 Atlantic, being determined by the descent 

 of the warm salt water of the upper layers 

 to greater depths in the North than in the 

 South Atlantic. In the south-west Pacific 

 density is higher than elsewhere throughout 

 the Pacific, for a similar reason. 



At 500 fathoms the density of the water 

 is much higher in the North Atlantic than 

 any elsewhere observed, as also at 600 fathoms, 

 especially to the west of the Canary Islands, 

 pointing unmistakably to the undercurrent 



