ON MAGNETISM. 



SECTION I. 



PHYSICAL EXTENSION OF MAGNETISM, AND LIMITA- 

 TION OF ITS TREATMENT IN THE PRESENT WORK. 



1. Dissemination of magnetism through many com- 

 ponents of the earth, and probable cosmical extension of 

 magnetism. 



In ordinary observation, magnetism is scarcely 

 known except as existing in iron and especially in 

 steel, and as related in some obscure manner to the 

 earth. But there is reason to believe that it is one 

 of the most extensively diffused agents in nature. It 

 can be traced not only in iron but also in every sub- 

 stance into which iron (one of the most widely spread 

 substances in nature) enters into composition. It is 

 found in nickel and other substances, and even in some 

 gases. Wherever a galvanic current exists in nature, 

 whether produced by chemical action or appearing in 

 the thermo-electric form as originating from the effects 



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