24 THE OCEAN WOULD. 



the meteorological and climatic conditions which rule the develop- 

 ment of life; and this circulation could not exist at least, the 

 character of its waters would be completely changed if they were 

 fresh in place of salt. " Let us imagine," says M. J alien, " that 

 the sea, now entirely composed of fresh water, of one uniform 

 temperature from the Pole to the Equator, and from the surface to 

 its greatest depths ; the solar heat would penetrate the liquid beds 

 nearest to the Equator; it would dilate them, so as to raise them 

 above their primitive level ; by the single effect of gravitation, they 

 would glide on the surface towards the polar zones. The absence of 

 all solar radiation would tend, on the contrary, to cool and contract 

 them without this tendency. An exchange would be established 

 from the extremities towards the centre ; in other words, a counter 

 current of cold and heavy water, calculated to replace the losses occa- 

 sioned by the action of solar radiation, would descend from the Poles, 

 but quite maintaining itself beneath the light and warm current from 

 he Equator." 



In a like system of general circulation, the physical properties of pure 

 water, which attains its maximum of density seven degrees two seconds 

 F. below zero, would produce the most singular consequences. As its 

 temperature rose above that point, the water would become lighter, 

 having, consequently, a tendency to ascend towards the upper beds. After 

 this, the equatorial current, meeting in its progress towards the Poles 

 the cold water, would itself be cooled down ; and when its temperature 

 had reached four degrees below zero, being now heavier than the polar 

 current, would change places with it, descending until it reached water 

 equally dense, while the polar current would ascend. Hence would 

 arise a sort of confusion of currents which would give to a fresh-water 

 ocean the strangest results, disarranging every instant the regular 

 circulation of its waters. It could not be so, however, in an ocean of 

 salt water, which attains its maximum specific gravity at four degrees 

 eight seconds F. below zero. By evaporation at the surface it is con- 

 centrated and precipitated, and thus rendered denser than that imme- 

 diately below the surface. It consequently sinks, while the lower beds 

 come up to replace, in order to modify it, and in turn to be precipitated 

 in the same manner. " In this manner we find established a continually 

 ascending and descending movement, which carries down into the depths 

 of ocean the water wanned at the surface by the solar rays of the Torrid 



