THE NEW SCIENCE OF METEOROLOGY 







on the " hypsometrical configuration of the conti- 

 nents"; and he urges that "great meteorological phe- 

 nomena cannot be comprehended when considered in- 

 dependently of geognostic relations" a truth which, 

 like most other general principles, seems simple enough 

 once it is pointed out. 



With that broad sweep of imagination which charac- 

 terized him, Humboldt speaks of the atmosphere as the 

 " aerial ocean, in the lower strata and on the shoals of 

 which we live," and he studies the atmospheric phe- 

 nomena always in relation to those of that other ocean 

 of water. In each of these oceans there are vast per- 

 manent currents, flowing always in determinate direc- 

 tions, which enormously modify the climatic conditions 

 of every zone. The ocean of air is a vast maelstrom, 

 boiling up always under the influence of the sun's heat 

 at the equator, and flowing as an upper current tow- 

 ards either pole, while an undercurrent from the poles, 

 which becomes the trade- winds, flows towards the 

 equator to supply its place. 



But the superheated equatorial air, becoming chilled, 

 descends to the surface in temperate latitudes, and con- 

 tinues its poleward journey as the anti-trade-winds. 

 The trade-winds are deflected towards the west, be- 

 cause in approaching the equator they constantly pass 

 surfaces of the earth having a greater and greater 

 velocity of rotation, and so, as it were, tend to lag be- 

 hind an explanation which Hadley pointed out in 

 1735, but which was not accepted until Dalton inde- 

 pendently worked it out and promulgated it in 1793. 

 lu opposite reason, the anti-trades are deflected 

 towards the east ; hence it is that the western borders 



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