SCIENCE OF COMMON THINGS. 275 



What is electricity ? Means of exciting electricity. 



PART VIII. 



ELECTRICITY, GALVANISM, MAGNETISM, AND 

 ELECTRO-MAGNETISM, 



CHAPTEE I. 



ELECTRICITY. 

 1793 What is electricity t 



Electricity is one of those imponderable agents that 

 appear to be diffused through all nature, existing in all 

 substances without affecting their volume or their tem- 

 perature, or giving any indication of its presence when 

 in a latent state. When, however, it is liberated from 

 this repose, it is capable of producing the most sudden 

 and destructive effects, or of exerting powerful influences 

 by a quiet and long-continued action. 



1*793 How may electricity be called into activity f 



By mechanical power, by chemical action, by heat, 

 and by magnetic influence. 



17*94 What is the most ordinary way of exciting electricity f 



By friction. 



17*95 Do we know any reason why the means above enumerated should 

 develope electricity from its latent condition? 



We are entirely ignorant upon this 'subject. 



17*96 When you rub apiece of paper with India-rubber, why does it 

 adhere to the table f 



Because tlie friction of the India-rubber against the 

 surface of the paper developes electricity, to which this 

 adhesiveness is mainly to be attributed. 



17*97* Does electricity present any appearance by which it can be "known f 



No ; electricity, like heat, is in itself invisible, though 

 often accompanied by both light and heat. 



