560 CONDUCTORS AND jS'OX-COXDUCTORS. 



is only necessary to bring it in contact with the elec- 

 trified wire ; if the body is a conductor, it withdraws all 

 electricity from the wire, and the pendulum drops; if 

 an insulator, the pendulum is not affected by the con- 

 tact of wire and body. If a number of bodies are tried 

 in this manner, it will be found that all metals, char- 

 coal, wood, paper, vegetable fibre, are conductors, while 

 all those bodies which may be electrified by rubbing 

 when held in the hand are insulators. When the elec- 

 trified wire is touched with a splinter of wood or a strip 

 of paper, which have been first rendered perfectly dry 

 by warming them for some time, the pendulum will 

 not drop instantly, but will do so slowly; the reason is,- 

 that these bodies are bad conductors and withdraw the 

 electricity from the wire only gradually ; they would, in 

 fact, be insulators were it not for their tendency to ab- 

 sorb moisture from the air, and the more moisture they 

 absorb the better they conduct. That water is a con- 

 ductor is easily shown by moistening a n on conductor, 

 for example a stick of sealing-wax, all over with water; 

 if the electrified wire be now touched with it the pen- 

 dulum drops immediately. Glass rods which are 

 serviceable for electrical experiments are not easily 

 moistened all over; the water runs into single drops, 

 unconnected with one another, and therefore incapable 

 of conducting electricity : some kinds of glass, again, are 

 conductors as long as the coating of moisture which 

 they condense on their surface is not removed by 

 warming them. 



* Not all liquids are conductors. Fatty oils, for 

 example, are non-conductors, as may be shown by 

 covering a stick of sealing-wax with oil. Jn contact 



