CHAPTEE XIII. 



WEATHER PREDICTIONS. 



To predict with any great accuracy what 

 the weather will be from day to day is a some- 

 what complicated problem, and, as all of us 

 have reason to know, weather predictions 

 made by those who have the matter in charge 

 and are supposed to know all about it often 

 fail to come to pass. The real trouble is that 

 they do not know all about it. There are so 

 many conditions existing that are outside of 

 the range of barometers, thermometers, ane- 

 mometers, and telegraphs that no one can tell 

 just when some of these unknown factors will 

 step in to spoil our predictions. 



In very many cases, perhaps in a large ma- 

 jority of them, the predictions made by the 

 weather bureau substantially come to pass. 

 It has been stated in former chapters that the 

 changes of weather accompany the movements 

 of what are called cyclones and anti-cyclones, 

 the cyclone being accompanied by low baro- 

 metric pressure and the anti-cyclone by a 

 higher one. The winds of the cyclone move 



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