20 OCEANIC CIRCULATION OF WATER. 



of congelation. De Haven invariably found the temper- 

 ature of sea water under the ice 28 Fahr." in the 

 arctic regions. * 



The close analogy between many of the conditions 

 of the atmospheric and aquatic oceans has been already 

 referred to. And in no respect is it more striking 

 than in the wonderful system of circulation, caused by 

 variations of temperature: which in the atmosphere 

 creates the winds, and in the water the great ocean 

 currents; for it is now a matter of ascertained fact 

 that to the heat of the sun, as its originating source, 

 may be traced almost every movement, and every 

 meteorological change, which takes place throughout 

 the world, whether in the ocean or upon the terrestrial 

 surface of the earth, or in the atmosphere above it. f 



Among the many wonderful and important effects 

 produced by heat upon the ocean, is the turning of 

 immense masses of sea water into invisible aqueous 

 vapour, which is conveyed all over the world by the 

 winds, and thus, becoming purified from its saline 

 particles, is made at length to fall in the form of rain 

 to fertilize the soil, and by its vivifying influence caus- 

 ing every form of animal and vegetable life to live 

 and flourish. Also portions of its surplus, after con- 

 ferring all these numerous blessings upon the inhabitants 

 of the land, sink into the ground at the higher eleva- 

 tions, and so produce the watersprings which issue 

 forth from the living rock at the lower levels, for the 

 sustenance of man and animals; and finally, having 



* The Physical Geography of the Sea, by Lietenant Maury, U.S.N., 

 1877, i6th edit., p. 282. 



j See Heat a Mode of Motion, by Professor Tyndall, ;th edit.,. 

 P- 478. 



