Self-induction of Wires. 79 



have one word for two ; next, to avoid confusion with 

 mechanical elasticity ; and thirdly, to harmonize with the 

 nomenclature I have used for some time past. Thus : — 



Flux. Force. 



n ' j x- '" n i f Resistivity. Resistance. 1 -™, , . 



(Jonduction-Uurrent. < n 3 ,./., n , , VHiiectric. 



I Conductivity, Conductance. J 



Induction .... Inductivity. Inductance. Magnetic. 



-r,. t , f Elastivity, Elastance. ) ™ , . 



Displacement . . < -r> .... •, t> -l± VJidectric. 



r ( r ermittivity. Permittance. J 



The elastance of a condenser is the reciprocal of its capacity, 

 and elastivity is the elastance per unit volume, as resistivity 

 is the resistance per unit volume, and conductivity the con- 

 ductance per unit volume. As for " permittivity " and " per- 

 mittance," there are not wanting reasons for their use instead 

 of u specific inductive capacity }> (electric), and u electrostatic 

 capacity/'' The word capacity alone is too general ; it must 

 be capacity for something, as electrostatic capacity. It is an 

 essential part of my scheme to always use single and unmis- 

 takable words, because people will abbreviate. Again, capa- 

 city is an unadaptable word, and is altogether out of harmony 

 with the rest of the scheme. Now the flux concerned is the 

 electric displacement, involving elastic resistance to yielding 

 from one point of view, and a capacity for permitting the 

 yielding from the inverse ; h^nce elastance and permittance, 

 the latter being the electrostatic capacity of a condenser. 

 There are now only two gaps left, viz. for the reciprocals of 

 inductivity and inductance. " Resistance to lines of force " 

 and " magnetic resistance " will obviously not do for per- 

 manent use.] 



If this restriction be removed, we have self- and mutual 

 induction concerned, and interferences ; or, even if there be 

 no external conductors, we have still the electric current of 

 elastic displacement, and with it electric and magnetic energy 

 outside the double tube. But, ignoring these, we have the 

 following striking peculiarities : — Rutting on one side the 

 question of the propagation of disturbances into the conductors, 

 which is so interesting a one in itself, we find that the elec- 

 trical constants are three in number — the resistance, capacity, 

 and inductance of the double-tube per unit of its length ; 

 whilst the .electrical variables are two — the current in each 

 conductor, and their difference of potential. The effective 

 resistance per unit length is the sum of their resistances, 

 which may be divided between the two conductors in any 

 ratio ; the capacity is that of the dielectric between them ; 



