THE WEATHER 35 



is the same, regardless of whether the air is moving east, 

 west, north, south, or in some intermediate direction, the air 

 about a " low " will all circle about it before reaching the 

 center. Each mass of air will travel in a spiral direction, 

 and the whole body of air about the " low " will rotate. The 

 action of the air is like that of water when it is running 

 through a hole in the bottom of the vessel containing it. We 

 must therefore think of a " low " as a great whirlpool of air 

 sometimes as much as a thousand miles in diameter and 

 moving slowly eastward. Such a great spiral whirl is called 

 a cyclone. The cyclone must not be confused with a very 

 destructive storm that sometimes occurs in our country 

 and is often called a cyclone, although the proper name 

 is tornado (see sect. 40). 



The air about a " high" will be deflected to the right and thus 

 will circulate spirally outward. This is called an anti-cyclone. 



33. Temperature in a cyclone. When warm winds blow to 

 a cooler part of the country, they cause it to become warmer, 

 as when a south wind blows over the northern states and pro- 

 duces higher temperature. Likewise a wind from the cold 

 plains of the northwest in winter may carry a freezing tem- 

 perature all the way to the gulf coast. Since, as we have seen, 

 the winds come into a cyclone from all directions, it follows 

 that there must be parts of it in which cool air is going south- 

 ward and cooling warmer places, and other parts of the storm 

 in which warm air from the south is carrying warm weather 

 northward. Let us take for the moment the case of the warm 

 air from the south and its effects on tempeiatures in the 

 cyclone. If we refer to any of our diagrams of cyclones or 

 to the weather maps, we see that the spiral course of the air 

 which comes into the " low " from the south carries it a little 

 to the east of the center of the " low." This means, of course, 

 that the eastern part of the storm will have southerly and 

 warm winds. The western part, on the contrary, will con- 

 sist of air which is coming from the north or northwest and 



