38 CHAMBERLIN— A POSSIBLE REVERSAL [April 18 



In an endeavor to find some measure of the rate of the abysmal 

 circulation, it became clear that the agencies which influenced the 

 deep-sea movements in opposite phases were very nearly balanced. 

 From this sprang the suggestion that if their relative values were 

 changed to the extent implied by geological evidence there might be 

 a reversal of the direction of the deep-sea circulation and that this 

 might throw light on some of the strange climatic phenomena of the 

 past and give us a new means of forecast of climatic states in the 

 future. 



That the deep-sea circulation is now actuated dominantly by 

 polar agencies is clear from the low temperatures of the abysmal 

 waters, even beneath the tropics. It is a firm inference that cold 

 waters creep slowly along the depths from the polar seas equator- 

 ward where they gradually rise to the surface and return on more 

 superficial routes. This is not, however, yet a matter of observation 

 and the courses pursued are unknown. It is perhaps more probable 

 that they are gyratory or spiral and complex than that they are 

 simple and direct. 



The agencies that affect oceanic circulation include at least : ( i ) 

 wind, (2) atmospheric transfer, (3) dift'erences of salinity, and (4) 

 differences of temperature, including freezing and thawing. The 

 earth's rotation of course modifies the currents but does not actuate 

 them. 



I. The effect of the wind is superficial and familiar, and need 

 only be considered here in so far as it affects the deep-sea circula- 

 tion. Its currents constitute horizontal circuits, and their frictional 

 effect upon the deep currents is probably slight and of a gyratory 

 phase in the main. In so far as they are strictly horizontal, they 

 doubtless favor equally poleward and equatorward movement in the 

 abysmal waters. If there is a component of their sum-total that 

 favors the piling up of waters in the polar regions, it must favor 

 the present deep circulation. If the opposite is true, it must antag- 

 onize it. There seems no way at present to measure the relative 

 amounts of these opposing tendencies. It is plausible enough to 

 reason that the cold air from the polar regions would flow more 

 largely at the base of the atmosphere than would the warmer air 

 from the equatorial regions and that the polar winds would thus 



