THE NEW SCIENCE OF METEOROLOGY 



diacal light, it is true, but this is of little aid, for the 

 zodiacal light, though thought by some astronomers to 

 be due to meteor swarms about the sun, is held to be, 

 on the whole, as mysterious as the aurora itself. 



Whatever the exact nature of the aurora, it has long 

 been known to be intimately associated with the phe- 

 nomena of terrestrial magnetism. Whenever a brill- 

 iant aurora is visible, the world is sure to be visited 

 with what Humboldt called a magnetic storm a 

 " storm" which manifests itself to human senses in no 

 way whatsoever except by deflecting the magnetic 

 needle and conjuring with the electric wire. Such 

 magnetic storms are curiously associated also with 

 spots on the sun just how no one has explained, 

 though the fact itself is unquestioned. Sun-spots, too, 

 seem directly linked with auroras, each of these phe- 

 nomena passing through periods of greatest and least 

 frequency in corresponding cycles of about eleven 

 years' duration. 



It was suspected a full century ago by Herschel that 

 the variations in the number of sun-spots had a direct 

 effect upon terrestrial weather, and he attempted to 

 demonstrate it by using the price of wheat as a criterion 

 of climatic conditions, meantime making careful obser- 

 vation of the sun-spots. Nothing very definite came 

 of his efforts in this direction, the subject being far too 

 complex to be determined without long periods of ob- 

 servation. Latterly, however, meteorologists, particu- 

 larly in the tropics, are disposed to think they find 

 evidence of some such connection between sun-spots 

 and the weather as Herschel suspected. Indeed, Mr. 

 Meldrum declares that there is a positive coincidence 



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