114 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XII.) 



the point so near that sonorous brushes passed, then the current of air instantly 

 ceased, and the surface of the water became level. 



1441. The discharge by a brush is not to all the particles of air that are near the 

 electrified conductor from which the brush issues ; only those parts where the rami- 

 fications pass are electrified : the air in the central dark parts l?etween them re- 

 ceives no charge, and, in fact, at the time of discharge, has its electric and induc- 

 tive tension considerably lowered. For consider fig. 14. to represent a single positive 

 brush ; — the induction before the discharge is from the end of the rod outwards, in 

 diverging lines towards the distant conductors, as the walls of the room, &c., and a 

 particle at a has polarity of a certain degree of tension, and tends with a certain 

 force to become charged ; but at the moment of discharge, the air in the ramifica- 

 tions h and d, acquiring also a positive state, opposes its influence to that of the po- 

 sitive conductor on «, and the tension of the particle at a is therefore diminished 

 rather than increased. The charged particles at h and d are now inductive bodies, 

 but their lines of inductive action are still outwards towards the walls of the room ; 

 the direction of the polarity and the tendency of other particles to charge from these, 

 being governed by, or in conformity with, these lines of force. 



1442. The particles that are charged are probably very highly charged, but, the 

 medium being a non-conductor, they cannot communicate that state to their neigh- 

 bours. They travel, therefore, under the influence of the repulsive and attractive 

 forces, from the charged conductor towards the nearest uninsulated conductor, or 

 the nearest body in a diffierent state to themselves, just as charged particles of dust 

 would travel, and are then discharged; each particle acting, in its course, as a centre 

 of inductive force upon any bodies near which it may come. 



1443. The travelling of these charged particles when they are numerous, causes 

 wind and currents, but these will come into consideration under carrying discharge 

 (1319.). When air is said to be electrified, and it frequently assumes this state 

 near electrical machines, it consists, according to my view, of a mixture of electrified 

 and unelectrified particles, the latter being in very large proportion to the former. 

 When we gather electricity from air by a flame or by wires, it is either by the actual 

 discharge of these particles, or by eflfects dependent on their inductive action, a case 

 of either kind being produceable at pleasure. That the law of equality between the 

 two forces or forms of force in inductive action is as strictly preserved in these as 

 in other cases, is fully shown by the fact, formerly stated (1173. 1174.), that, however 

 strongly air in a vessel might be charged positively, there was an exactly equal 

 amount of negative force on the inner surface of the vessel itself, for no residual 

 portion of either the one or the other electricity could be obtained. 



1444. I have nowhere said, nor does it follow, that the air is charged only where 

 the luminous brush appears. The charging may extend beyond those parts which 

 are visible, i. e. particles to the right or left of the lines of light may receive electri- 



