'electricity. 371 



the friction of resla, was, etc., it has been inferred that 

 there are two kinds or states of electricity — the one called 

 vitreous, because especially developed on glass, and the 

 other resinous, because first noticed on resinous sub- 

 stances. 



What is the The fundamental law which governs the re- 

 &Tc^trfJai*\^ lation of these two electricities to each other, 

 rep^iasToar*"'* and which constitutes the basis of this depart- 

 ment of physical science, may be expressed as 

 follows : — 



Like electricities repel each other, unlike electricities 

 attract each other. 



Thus, if two substances are charged with vitreous electricity, they repel 

 each otherj two substances charged with resinous electricity also repel each 

 other ; but if one is charged with vitreous, and the other with resinous elec- 

 tricity, they attract each other. 



whenisabody '^^^- Wlicu a body holcls its own natural 

 non-electrified? quantity of elcctrlcity undisturbed, it is said 

 to be non-electrified. 



"When an electrified body touches one that 

 trifled body is non-electrlficd, the electricity contained in 

 non-electrified, the formcr is transferred in part to the latter. 



what occurs ? 



Thus, on touching the end of a suspended silk thread with a 



piece of excited wax or glass, electricity will pass from the wax or glass into 



the silk, and render it electrified; and the silk will exhibit the effects of the 



electricity imparted to it, by moving toward any object that may be placed 



near it. 



736. Two theories, based upon the phenom- 

 ories have been eua of attraction and repulsion, have been 

 count for eiec- formcd to account for the nature and origin of 



electricity. These two theories are known as 

 the theory of two fluids, and the theory of the single fluid ; 

 or the theory of Da Fay, an eminent French electrician, 

 and the theory of Dr. Franklin. 



737. The theory of two fluids, or the theory 

 theory of two of Du Fay, supposcs that all bodies, in their 



natural state, are pervaded by an exceedingly 

 thin subtle fluid, which is composed of two constituents, 



