174 Velocity of the Electric Current. 



If the celerity of the motion of the armature, is propor- 

 tional to magnitude of the force acting on it, then, our ap- 

 parent velocities ought to be directly proportional to the 

 magnetic force of the current. If this is found to be the case 

 our results can only be regarded as mechanical effects, en- 

 tirely distinct from the real velocity of the electric wave. 



Ohm's celebrated law enables us to compute the mag- 

 netic forces for circuits of all kinds, and from these, to 

 deduce the relative ratios of the velocities. 



The general formula? is 



er 



— Magnetic force of the current. 



J = n R + r J = 



e = Electro-motive force. 

 n = Number of battery elements. 

 11= Resistance of one battery element. 

 r = All the other resistances in the cir- 

 cuit. 



This formulas will be somewhat modified by the escape, 

 but as the amount was not measured, the computation will 

 be made without taking it into account. 



If we make the resistance of the relays equal to 200 

 miles of line wire (which cannot be more than tV in error,) 

 and will not materially aftect the computation, we will 

 have the following equations, for the expression of the 

 magnetic force, for the four experiments of May -Tth. 



73= s 



70 e 70 e 



