CHARGE BY CASCADE. 73 



Adding all these equations, we get 



Hence the charge of the first jar, which is the only one that 

 receives electricity directly, is 



v,-v, 



I I I 



c + c + c 7/ 



We have thus, for the capacity Cj of the battery, 



If the jars are identical, the capacity of the battery has become 

 / times less than that of each of the jars. 



This arrangement may appear unfavourable, since its effect is to 

 diminish greatly the capacity of the battery; yet it presents great 

 advantages for certain experiments. Leyden jars can only sustain a 

 limited difference of potential, beyond which their coatings discharge 

 themselves along the surface of the glass, and even sometimes 

 through the mass of the glass itself, which is then traversed by a 

 spark. By means of a battery in cascade, the total difference of 

 potential may be distributed in stages on the successive jars. 



This, for instance, is the arrangement adopted in the ordinary 

 Holtz machines, where the capacity of the conductors is increased 

 by connecting each of them with the inner coating of a Leyden jar ; 

 care however is taken to join these in cascade, so as to maintain the 

 maximum difference of potential, and therefore the greatest striking 

 distance which the play of the machine allows. 



When a large number of jars are available, they may be joined 

 together for quantity so as to form several batteries, which in turn 

 are arranged in cascade. In this way the whole of the potential 

 which a machine can yield may be utilised, and the maximum of 

 effect obtained with the least expenditure of electricity. 



