CHAP, i.] ELECTRICITY AND MAGNETISM. 



5 



toward the hand, as the rubbed body in Fig. 3 did. 

 This proves that the feather, though it has not itself 

 been rubbed, possesses the property originally imparted to 

 the rod by rubbing it. In fact, it has become electrified, 

 by having touched an electrified body which has given 

 part of its electricity to it. It would appear then that 

 two bodies electrified with the same electricity repel one 

 another. This may be confirmed by a further experi- 

 ment. A rubbed glass rod, hung up as in Fig. 3, is 

 repelled by a similar rubbed glass rod ; while a rubbed 

 stick of sealing-wax is repelled by a second rubbed stick 

 of sealing-wax. Another way of showing the repulsion 

 between two simi- 

 larly electrified bodies 

 is to hang a couple 

 of small pith- balls, 

 by thin linen threads 

 to a glass support, 

 as in Fig. 5, and 

 then touch them both 

 with a rubbed glass 

 rod. They repel one 

 another and fly apart, 

 instead of hanging 

 down side by side, 

 while the near pre- 

 sence of the glass rod will make them open out still 

 wider, for now it repels them both. The self-repulsion 

 of the parts of an electrified body is beautifully illustrated 

 by the experiment of electrifying a soap-bubble, which 

 expands when electrified. 



4. Two kinds of Electrification. Electrified 

 bodies do not, however, always repel one another. The 

 feather which (see Fig. 4) has been touched by a rubbed 

 glass rod, and which in consequence is repelled from 

 the rubbed glass, will be attracted if a stick of rubbed 

 sealing-wax be presented to it ; and conversely, if the 



Fig. 5- 



