The Weather 21 



away from the center. Because of this feature the high pressure 

 area is called an anticyclone. 



Over the eastern section of the continent, winds from a high- 

 pressure area in the south move in an easterly direction rather 

 than due north toward a low area in the north. A rule has been 

 formulated which enables one to determine the direction winds 

 actually have. It runs, " Stand with your left hand pointing 

 toward the northern low and your right hand pointing toward 

 the high, and the wind will be blowing on your back." In the 

 southern hemisphere the wind would blow on your face. Why 

 are winds deflected thus from the due northern or southern 

 direction? This question must now be considered. 



Winds starting from a high-pressure region in the south toward 

 a low-pressure area due north are deflected toward the east, as 

 you find indicated on the weather maps. This is due to the 

 rotation of the earth about its axis. How this result is brought 

 about may be suggested in this way: A hunter seeing a duck 

 flying due east plans to shoot it when it is directly north of 

 him. Where must he aim in order to hit the duck : directly at 

 it, or ahead, or behind it? Or, suppose you are on a train 

 that is running due east at a rate of sixty or more miles an 

 hour. A post that will be passed stands several hundred 

 yards north of the track. As you pass it, you are to aim a 

 rifle directly at it. Will the bullet thus aimed hit the post? 

 If not, to which side of the post will it go ? 



Consider now a similar case, but more clearly connected 

 with the central problem. A fixed point on the equator is 

 moving due east through a distance of 1000 miles an hour. 

 Another fixed point due north on the 45th parallel is moving 

 through a distance of about 750 miles per hour; and another 

 fixed point due north on the 60th parallel about 500 miles an 

 hour ; while at the pole the distance traversed would be about 

 zero. Now imagine a very powerful gun located on the equator 

 and aimed at the fixed point due north on tne 45th parallel. 

 The bullet is supposed to keep at a uniform distance from the 



