ELEMENTARY LESSONS ON [CHAP. i. 



amber and jet, but a very large number of substances, 

 such as diamond, sapphire, rock-crystal, glass, sulphur, 

 sealing-wax, resin, etc., which he styled electrics?- 

 possess the same property. Ever since his time the 

 name electricity has been employed to denote the 

 agency at work in producing these phenomena. Gilbert 

 also remarked that these experiments are spoiled by the 

 presence of moisture. 



Fig. i. 



2. A better way of observing the attracting force is 

 to employ a small ball of elder pith, or of cork, hung by 

 a fine thread from a support, as shown in Fig. 2. A 

 dry warm glass tube, excited by rubbing it briskly with 

 a silk handkerchief, will attract the pith ball 'strongly, 

 showing that it is highly electrified. The most suitable 

 rubber, if a stick of sealing-wax is used, will be found to 



1 " Electrica ; quae attrahunt eadem ratione ut electrum." (Gilbert). 



