112 IRature'0 /HMractes, 



classes originate on about the same line, a little 

 west, say, north of Montana, moving first in 

 a southeasterly direction, passing over the cen- 

 ter of Lake Michigan and bending northerly 

 through Lake Ontario and finally landing in 

 the Gulf of St. Lawrence. Two other classes 

 start at the same point, one of them going as 

 far south as Cincinnati, and the other as far 

 south as Montgomery, Ala., and both turning 

 at these points northeasterly to the Gulf of St. 

 Lawrence. Two other classes originate in 

 Colorado, one moving in a northeasterly di- 

 rection slightly curved, and the other directly 

 east. Still others have their origin farther 

 south in the Gulf of Mexico, and move in a 

 northeasterly direction. Very rarely they 

 originate in the Atlantic east of Savannah, 

 moving first in a northwesterly direction, but 

 finally bending to the northeast. 



Every day there is a weather map made up 

 showing the locations of the high and low 

 barometers, direction of wind, lines of equal 

 pressure, as well as those of temperature. By 

 study from year to year all of these phe- 

 nomena have become systematized, so that by 

 tracing an area of low barometer from its 

 origin in its progress easterly it is soon seen 

 to fall under one of these classes and we are 

 able to predict about what its course will be. 

 Knowing the speed of its movement as well as 

 the velocity of wind and all the conditions at- 



