168 M. Henrici on the Theory and Application of Electricity, 



is diffused over the two conductors lying in contact. This 

 latter portion however may be further carried away by con- 

 duction, and it is evident that by contact compensation must 

 ensue for that which is thus carried away (perhaps absorbed 

 by a condenser, or in some other way). 



If the conduction be now completed in a manner requiring 

 no further action by contact, an electric current is produced, 

 the power of which must evidently be proportional to the per- 

 fection of the whole conduction, because in any given time a 

 certain quantity only of electricity can escape at the point of 

 contact. This quantity of electricity however always amounts 

 to a very small portion only of that originally produced by the 

 contact, as even the best conduction presents a remarkably 

 greater resistance than the point of contact itself. 



Thus the internal condition of an open galvanic series* 

 cannot be compared with a charged electrical jar, because in 

 this the electricities conveyed to it from without are artificially 

 separated from one another by an intervening non-conductor 

 and prevented from neutralizing each other. But even here 

 a certain amount of electricity, although it is but small, and 

 proportional to the conducting power of the separating non- 

 conductor, must evidently pass through this to produce neu- 

 tralization. The discharge of the jar ensues when any better 

 conduction than by means of the non-conductor is presented 

 to the electricities, as for instance, by the air, or still more the 

 earth (which affords in the case of Volta's pile very imper- 

 fect conduction). Consequently, an electric jar, if no dis- 

 charge occurred through the air, would almost entirely part 

 with the electricity communicated to it by rapid discharge 

 through the completed circuit, whilst of the electricity pro- 

 duced by contact a small quantity only can ever be collected 

 and made effective at one time. 



From these considerations, it cannot be allowed that the 

 electricity from contact in the experiments we have investi- 

 gated is capable of being rendered perceptible to the electro- 

 scope without condensation, because, as we have stated, even 

 between unvarnished and very small metallic surfaces conden- 

 satory effects occur. I have succeeded, by the following method 

 of proceeding, in making the electricity of contact unequivo- 

 cally perceptible without condensation. A strip of silver was 

 fastened to one end of a strip of zinc, the whole was then bent 

 into the form of a U ; between the two arms a narrow strip of 

 gold leaf was suspended, so that it could be moved without 



* By an open but complete series, as is well known, we understand one 

 in which, if we adopt the contact theory, the series is complete, as ex- 

 pressed l)y the formula, " Copper— zinc — liquid — copper." 



