OCEANIC CIRCULATION 121 



areas of high barometric pressure (anti- 

 cyclonic areas) situated over the oceans prac- 

 tically all the year round, out of which winds 

 blow in all directions towards the surrounding 

 regions where atmospheric pressure is lower ; 

 for instance, the trade-winds blow into the 

 equatorial low pressure area from both sides. 

 In these anticyclonic regions of the oceans 

 calms and light variable winds prevail, and 

 this necessarily implies vast accessions of air 

 setting towards them as upper aerial currents, 

 thence slowly descending to the surface of the 

 sea to take the place of the air passing out as 

 surface winds ; the result is that in these 

 regions the air is relatively very dry, evapora- 

 tion is very great, and the specific gravity 

 of the surface water is high. Not only is the 

 barometric pressure in these anticyclonic 

 areas usually very high, but the oscillations of 

 the barometer are very small. Thus the 

 " Challenger " observations in the anti- 

 cyclonic areas of the great oceans showed 

 in the South Pacific in lat. 35° S. a difference 

 between the morning maximum and the 

 afternoon minimum of only 036 inch ; in 

 the North Pacific in lat. 36° N. this difference 

 was only 025 inch, or less than a third of 

 what occurs near the equator ; in the South 

 Atlantic the difference was also 025 inch, 

 while in the North Atlantic it was only 



