98 SEASIDE DIVINITY. 



and less salt, on which in its turn the process of 

 evaporation acts, and which again sinks only to 

 give place to another supply. And thus in per- 

 petual succession different layers of surface-water 

 are subjected to the same process, each sinking 

 down afterwards by reason of its increased specific 

 gravity. In the Red Sea and the Mediterranean, 

 which we take as examples, the waters at a great 

 depth are considerably heavier than those at the sur- 

 face, and by a familiar physical law flow outwards 

 by their own weight in an under-current, while their 

 place is supplied by a surface-current, which, as 

 already stated, flows inward from the ocean. Now 

 in fresh water this system of currents could not 

 occur, because evaporation from the surface of 

 fresh water does not make any change in the 

 specific gravity of the water subjected to the im- 

 mediate action of the process. 



The cause thus explained as regards the two in- 

 land seas now referred to is also greatly concerned 

 in the much vaster system of circulation which 

 takes place in the ocean itself; as, for instance, in 

 the under-current of salter and heavier water that 

 flows from the equator toward the poles, and the 

 surface-current of water lighter and less salt that 

 flows in a contrary direction. 



But while it is certain that the saltness of the 

 sea in relation to the process of evaporation has 

 much concern in the system of circulation between 

 one part of the ocean and another, other con- 

 siderations there are which show that the chemical 

 constitution of the sea-water, independently of 

 evaporation, adapts it to this office. 



