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ELEMENTARY LESSONS 



ON 



ELECTRICITY & MAGNETISM. 



CHAPTER I. 



FRICTIONAL ELECTRICITY. 



LESSON I. Electrical Attraction and Repulsion. 



1. Electrical Attraction. If you take a piece of 

 sealing-wax, or of resin, or a glass rod, and rub it upon 

 a piece of flannel or silk, it will be found to have ac- 

 quired a property which it did not previously possess : 

 namely, the power of attracting to itself such light 

 bodies as chaff, or dust, or bits of paper (Fig. i). This 

 curious power was originally discovered to be a property 

 of amber, or, as the Greeks called it, vjXtKrpoVy which is 

 mentioned by Thales of Miletus (B.C. 600), and by 

 Theophrastus in his treatise on Gems, as attracting light 

 bodies when rubbed. Although an enormous number of 

 substances possess this property, amber and jet were the 

 only two in which its existence had been recognised by 

 the ancients, or even down to so late a date as the time 

 of Queen Elizabeth. About the year 1600, Dr. Gilbert 

 of Colchester discovered by experiment that not only 



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