172 



POPULATIONS OF THE SEA 



climatic change; and Rukhin (1957) and Durham (1959) have 

 summarized paleoclimatic indicators and manifestations. The 

 slender classic by Dubois (1895) is as nice an illustration as we 

 have of the nature of the geologic evidence and reasoning, despite 

 the 65 years that have elapsed since it was published. And, for 

 the future, the way to more rigorous analysis of paleooceano- 

 graphic data and reproduction of ancient marine currents has 

 been outlined by Stommel (1957) and von Arx (1957). 



SALINITY 



HEAVY PRECIPITATION 



SINKING 

 AIR 



RISING ^-* — 0° — 

 AIR 



HEAVY PRECIPITATION 



VARIABLE WINDS AND CALMS 

 LARGE EVAPORATION 



no VARIABLE WINDS AND CALMS 

 HEAVY PRECIPITATION 



VARIABLE WINDS AND CALMS 

 LARGE EVAPORATION 



Fig. 6. Schematic tropospheric wind system for a hypothetical water-covered 

 earth with strong latitudinal temperature gradient and mean annual salinities of 

 present surface waters (slightly modified after Fleming in Hedgpeth, 1957, pp. 

 90-91). 



From these and other works we know that the rotation and 

 frictional effects of the earth, the position of the polar axis, the 

 pull of the sun on the equatorial bulge, secular variations of the 

 solar heat budget, and thermal variations of the atmosphere are 

 responsible for the major wind fields — their location, orientation, 

 breadth, and strength — and that wind patterns and size and 

 orientation of land masses are the principal determinants of ocean 

 currents. If, to these, we add the Coriolis deflection, the monsoon 



