ELEMENTARY LESSONS ON [CHAP. i. 



end of a glass rod as a handle. The reason of this 

 precaution will be explained toward the close of this 

 lesson, and more fully in Lesson IV. 



A large number of substances, including iron, gold, 

 brass, and all the metals, when held in the hand and 

 rubbed, exhibit no sign of electrification, that is to say, 

 do not attract light bodies as rubbed amber and rubbed 

 glass do. Gilbert mentions also pearls, marble, agate, 

 and the lodestone, as substances not excited electrically 

 by rubbing them. Such bodies were, on that account, 

 formerly termed non - electrics ; but the term is erro- 

 neous, for if they are fastened to glass handles and then 

 rubbed with silk or fur, they behave as electrics. 



3. Electrical Repulsion. When experimenting, 

 as in Fig. i, with a rubbed glass rod and bits of chopped 

 paper, or straw, or bran, it will be noticed that these 



little bits are first attracted 

 and fly up towards the ex- 

 cited rod, but that, having 

 touched it, they are 

 speedily repelled and fly 

 back to the table. To 

 show this repulsion better, 

 let a small piece of feather 

 or down be hung by a silk 

 thread to a support, and 

 let an electrified glass rod 

 be held near it. It will 

 dart towards the rod and 

 stick to it, and a moment 

 later will dart away from 

 it, repelled by an invisible 

 force (Fig. 4), nor will it 

 again dart towards the rod. If the experiment be 

 repeated with another feather and a stick of sealing-wax 

 rubbed on flannel the same effects will occur. But, if 

 now the hand be held towards the feather, it will rush 





Fig. 4. 



