5^ 



JOURNAL ()¥ THE 



Suppose A B (in the fig.) to be the line of the southern edge of 

 the cloud formation and the line along which the wind S, S, S, &c., 



from the southwest meet 



QJ 



A 



from 



the wind N, N, &c. 

 the north and west. 



Let S O and N Q repre- 

 sent these winds in mag- 

 nitude and direction. &• 

 Q is necessarily greater 

 than N Q. 



The effect of these 

 winds upon the air at the 

 place of meeting will be 

 best determined by resolv- 

 ing them in directions 

 perpendicular and paral- 

 lel to A B. NX and S Y 

 will be the components 

 perpendicular to A B, and 

 (^^ X Q and Y O those paral- 

 ' lei. If N X is equal to S 

 Y the air at (O Q) will not 

 be urged out of the line 

 A B, and also Y O will be 

 greater than X Q ; hence 

 the air at (O Q) will be 

 made to rotate opposite 

 the hands of a watch. A 

 rotating mass of air may 

 be regarded as an isolated 

 mass and capable of be- 

 ing acted on by the pres- 

 sure of wind, especially 

 as these forces tend to 

 ^ preserve and accelerate 

 this motion. 



Hence the components 

 N X and S Y being equal 

 and opposite neutralize 

 "^ each other, leaving X Q 



and Y O as the effective components, which because they are unequal 

 in magnitude produce rotation and because they act in same "direc- 

 tion A B produce translation. 



