404 Dr. Faraday on the Physical Character of 



the conditions of the two former cases. The power (and its lines) 

 here requires the presenceoi two or more acting particles or masses, 

 as in the case of gravity ; and cannot exist with one only, as in 

 the case of light. But though two particles are requisite, they 

 must be in an antithetical condition in respect of each other, and 

 not, as in the case of gravity, alike in relation to the force. The 

 power is now dual ; there it was simple. Requiring two or more 

 particles like gravity, it is unlike gravity in that the power is 

 limited. One electro-particle cannot affect a second, third and 

 fourth, as much as it does the first ; to act upon the latter its 

 power must be proportionately removed from the former, and 

 this limitation appears to exist as a necessity in the dual cha- 

 racter of the force ; for the two states, or places, or direction of 

 force must be equal to each other. 



3249. With the electric force we have both the static and 

 dynamic state. I use these words merely as names, without 

 pretending to have a clear notion of the physical condition which 

 they seem meaningly to imply. Whether there are two fluids or 

 one, or any fluid of electricity, or such a thing as may be rightly 

 called a current, I do not know ; still there are well established 

 electric conditions and effects which the words static, dynamic, 

 and current are generally employed to express ; and with this 

 reservation they express them as well as any other. The lines 

 of force of the static condition of electricity are present in all 

 cases of induction. They terminate at the surfaces of the con- 

 ductors under induction, or at the particles of non-conductors, 

 which, being electrified, are in that condition. They are subject 

 to inflection in their course (1215. 1230.), and may be compressed 

 or rarefied by bodies of different inductive capacities (1252. 

 1277.) ; but they are in those cases affected by the intervening 

 matter ; and it is not certain how the line of electric force would 

 exist in relation to a perfect vacuum, i. e. whether it would be a 

 straight line, as that of gravity is assumed to be, or curved in 

 such a manner as to show something like physical existence se- 

 parate from the mere distant actions of the surfaces or particles 

 bounding or terminating the induction. No condition of quality 

 or polarity has as yet been discovered in the line of static electric 

 force ; nor has any relation oitime been established in respect of it. 



3250. The lines of force of dynamic electricity are either 

 limited in their extent, as in the lowering by discharge, or other- 

 wise of the inductive condition of static electricity, or endless 

 and continuous, as closed curves in the case of a voltaic circuit. 

 Being definite in their amount for a given source, they can still 

 be expanded, contracted, and deflected almost to any extent, 

 according to the nature and size of the media through which 

 they pass, and to which they have a direct relation. It is pro- 



