SWIRLS OF THE SEA 



43 



the equator ; and the waters of the equator work 

 forever along the surface, moving outward tow- 

 ard the poles. 



There is a similar interchange of waters by 

 force of gravity in the majority of inland seas. 

 The evaporation from the surface of the lied 

 Sea is estimated at eight solid feet a year, and 

 from the Mediterranean in corresponding pro- 

 portion. This is enormous, and is not compen- 

 sated for by a sufficient rainfall or inward 

 river flow. Both seas would have crystalized 

 into salt beds centuries ago were it not that 

 through the Straits of Gibraltar and the Straits 

 of Babel Mandeb a heavy salt water current 

 goes out and a current of lighter, fresher water 

 pours in. Even now the salinity of those seas 

 is very high and the exchanging currents of 

 water through the entrances are hard pushed to 

 maintain normal conditions. 



In a like manner difference in temperature 

 may be accounted a cause of sea currents — a 

 contributory cause of difference in gravity. 

 The body of heat must be equal to the body of 

 cold, otherwise the sea would grow hotter or 

 colder, just as the body of rainfall must equal 

 the body of evaporation, otherwise the sea 

 would grow less or greater. Wherever the one 

 predominates it flows over and mingles with 



Interchange 

 of waters in 

 Red Sea 

 and Medi- 

 terranean. 



Differercc 

 in tern pera- 

 tiire a cause 

 of circula- 

 tion 



