38 ELEMENTS OF STATIC ELECTRICITY. 



COMPARATIVE CONDUCTIVITY OF DIFFERENT SUB- 

 STANCES FOR HEAT AND ELECTRICITY, AS GIVEN BY 

 WlEDMANN AND FRANZ : 



Electric Conductivity. 



100 

 73 

 59 

 22 

 23 

 13 

 11 

 10 

 6 

 2 



Other observers place the electric conductivity of 

 some of these substances much higher, making the con- 

 ductivity of copper nearly equal to that of silver. 



If the electric wave has its own peculiar structure, it 

 is evident that a substance whose structure is adapted 

 to it, or whose molecules easily adapt themselves to it, 

 would be a conductor; while a substance whose struct- 

 ure is not so adapted, or whose molecules resist such 

 adaptation, would be a non-conductor. 



An attempt to insert a No. 36 screw into a No. 30 

 screw hole will fail, because the threads of the screws 

 are not adapted to each other. But let the same screw 

 be inserted into some yielding substance, as soft wood, 

 and the substance adapts itself to the structure of the 

 screw ; or, as we say, it cuts its own thread ; while a 

 rigid substance like iron resists such adaptation. 



Something analogous to this may constitute the 

 difference between conductors and non-conductors, 

 and may also be the cause of other electric phenomena 

 of equal importance. 



