30 STATIC ELECTRICITY 



with another, then sharing one of the half units with another, 

 and so on, we may suppose sub-multiples prepared on the scale 



i,J,i,&c. 



Imagined method of measuring any charge in 

 terms of the unit; We may now use these quantities some- 

 what as we use the weights of a balance. Suppose that we wish 

 to measure the quantity of electricity on a given body, let us 

 place it insulated within an insulated can connected to an electro- 

 scope. Then let us place within the can and also insulated from 

 it quantities of the opposite kind of electricity until the leaves of 

 the electroscope fall together. Then the two kinds are equal in 

 amount. It is evident that we may keep the can to earth while 

 we are inserting the charged body and the opposite quantities and 

 then test their equality by lifting them all out at the same time. 

 If the opposite charges are unequal the electroscope will at once 

 show a charge. 



