78 ELEMENTS OF STATIC ELECTRICITY. 



B, and C be well insulated on cakes of paraffin or some 

 equally good insulator. 



A positive charge given to the inner coating of A 

 will induce negative on its outer coating, by repelling 

 the same amount of electricity; and this repelled 

 charge must go to the inside of B, since it has no other 

 outlet. Hence the inner coating of B will be positively 

 charged, and electricit}^ will, in like manner, be repelled 

 from its outer coating to the inner of C. Hence the 

 charge of each jar in the series will be similar to that 

 of A ; electricity from the outer coating of D being 

 repelled to the earth. 



Fig. 21 Jars in Cascade. 



As the energy expended is distributed among four jars, 

 it is evident that the charge of each must be much less 

 than if the same amount had been expended in charging 

 one jar : since the energy accumulated cannot exceed 

 the energy expended. But, as the charge is in the 

 inverse ratio of the thickness of the glass, the resist- 

 ance from this source must increase from A to 7>, in 

 proportion to the number of thicknesses interposed : 

 and the charge must vary in the same ratio ; the neg- 

 ative being greatest on the outer coating of A, where 

 only one thickness is interposed, and least on the outer 

 coating of D, where four thicknesses are interposed ; 



