60 ELECTRICITY AND GALVANISM. 



The former they called positive electricity, the latter 

 negative. If a glass tube or ruler be excited by friction, 

 it will attract light bodies, as pith or feathers ; also if a 

 stick of sealing-wax be similarly excited, it will attract in 

 a similar manner. Here different causes conspire to 

 produce the like effects. According to the former theory, 

 which is known by the name of the theory of Du Fay, 

 although the two fluids exist in bodies in a state of inti- 

 mate union, yet, when separated, they become repulsive 

 with regard to themselves, and attractive of each other. 

 Thus the friction of the glass tube will separate the fluids, 

 and the vitreous electricity will attach itself to the glass, 

 which becomes attractive in order to restore the equili- 

 brium j or rather the vitreous electricity of the glass attracts 

 the resinous of the body, and at the same time carries the 

 body with it. According to the latter, which is called 

 the Franklinian theory, and which assumes that there 

 is but one kind of fluid, and that all bodies continue in 

 an electrified state as long as they retain a natural share 

 of it ; but, when the equilibrium is disturbed, as when 

 the electric is excited by friction, the electricity becomes 

 conveyed either from the rubber to the electric, or from 

 the electric to the rubber, according to the peculiar na- 

 ture of the electric employed. In the former case, the 

 electric is said to have a positive excitement, and will 

 attract light bodies in order to throw off its superabund- 

 ance of electricity ; in the latter it is said to have a negative 

 excitement, and will attract for the purpose of obtaining 

 its natural share. Philosophers of the present day still 

 continue divided as to the nature of electricity, and its 

 mode of action, some following the theory of Du Fay, 

 and some that of Franklin. 



Although writers on this subject generally state that 

 there are two kinds of electricity, yet it appears that 

 either kind may in some instances be produced from the 

 same body, by varying the nature of the rubber. Thus 

 sealing-wax excited by fur becomes negatively electrified ; 

 but excited by tinfoil, it will be positively electrified. 



To exhibit the most striking and important phenomena 

 of electricity, it is necessary to have an extensive appa- 

 ratus, which, in a work like the present, it is impossible 



