228 Prof. Dove's Outlines of a general Theory of the Winds. 



1. In the northern hemisphere, winds which begin as north 

 winds, in gradually advancing pass through NE., and become 

 more and more easterly. 



Supposing places, A A y A /; A //; 

 B B, B„ B„. 

 C C, C„ C lu 



so situated, that of A, B, C, D, being under the same meridian, 

 the place A is the most northern and D the most southern ; 

 of A A / A,i A,„ situated under the same parallel, A is the most 

 western, A //; the most eastern ; and that the whole bulk of air 

 contained between A A,„ and D D //y from any cause is put in 

 motion from north to south; then, if the air which had proceeded 

 from C C /; arrives nearly as a north wind in the parallel DD ///5 

 that coming from B B /// will arrive quite as a north-east wind, 

 while that arriving from A A u/ will appear still more as an 

 easterly wind. To an observer who is in D D t/I the vane will 

 thus have gradually turned from north through north-east to 

 east. 



2. In the southern hemisphere, winds that begin as south 

 winds, in gradually advancing pass through south-east and 

 become more and more easterly. 



If, therefore, ^ ^ ^ ^ 



° °\ *", £ 



b b b b 

 a a a a 



designate places of which those being under the parallel a a /t/ 

 are the most southerly, and those in the parallel d d M are the 

 most northerly, an observer being in d d jn will see the vane turn 

 gradually from S. through SE. to E. 



If in this manner an easterly wind shall have arisen in the 

 northern or southern hemisphere, it will pass through the 

 parallels D D w and d d /f/ without being at all modified by the 

 rotation of the earth. 



If the cause which drove the air to the equator continues, 

 the east wind, which is the consequence, will check the current. 

 The current being thus checked, the air will soon acquire 

 the velocity of rotation of the place beneath ; it will join it in 

 a state of relative rest. With a continual tendency to stream 

 towards the equator, exactly the same phenomena will be re- 

 peated which we have just examined. 



Let us now suppose that the equatorial currents appear after 

 the polar currents have prevailed for a while. In the northern 

 hemisphere a rising south wind will take the place of the 

 polar current, grown more or less easterly by shifting from 



