YIELD OF MACHINES. 185 



from this is deduced 



m V nc 



7 <C~<! ; j 



nc V m 

 or 



nn'cc >mm'. 



If this latter condition is realised at the outset (and it evidently 

 does not depend on the original electrification), the charge of 

 the machine will go on increasing. If the inequality is kept up 

 notwithstanding the increase of the coefficients m and m', the charge 

 will have no other limit than that which is determined by the pro- 

 duction of sparks. If the preceding inequality were in the contrary 

 direction, the charge would go on diminishing, and would rapidly 

 become null. 



When the apparatus is symmetrical, the condition for the increase 

 of the charge is simply 



nc>m. 



The preceding calculation applies particularly to the arrangement 

 in which the collector of one machine is in metallic connection with 

 the inductor of the other ; but the same method of reasoning, slightly 

 modified in details, would also apply to all multipliers of electricity 

 which act by reciprocal induction. 



197. YIELD OF MACHINES. Whatever, moreover, may be the 

 external cause limiting the charge, it will be seen that all these 

 machines act like true sources that is to say, as systems which by 

 the play of their own organs can maintain a conductor at a constant 

 potential, or maintain a certain difference of potential between two 

 conductors. 



This result is obtained when the quantity of electricity brought 

 to the conductor is at every instant equal to that taken away from 

 it, either by loss from contact with air, or by discharges between the 

 collector and the earth. The yield of the machine is the quantity 

 of electricity put in motion in each unit of time. It is clear that for 

 addition machines, the yield, other things being equal, is proportional 

 to the capacity of the carrier and to the number of operations 

 performed in each unit of time. If, as with plate machines, the 

 carrier acts continuously, the yield is proportional to the velocity. 



The phenomena in multiplication machines are not quite so 

 simple ; but experiment shows that the yield is sensibly proportional 

 to the velocity, although as a general rule it increases a little more 

 rapidly. 



