INDUCTIVE EFFECT AT THE COMMENCEMENT OF A CURRENT. 53 



electricity, and could have it highly increased, as we know by the former experi- 

 ments (1060.) by the opposite inductive action brought into activity at the moment 

 contact at Z or C was broken. 



1103. A galvanometer was then introduced at a?, and the deflection of the needle 

 noted whilst contact was continued at G and E : the needle was then blocked as 

 before in one direction (1087.)? so that it should not return when the current ceased, 

 but remain in the position in which the current could retain it. Contact at G or E 

 was broken, producing of course no visible effect ; it was then renewed, and the nee- 

 dle was instantly deflected, passing from the blocking-pins to a position still further 

 from its natural place than that which the constant current could give, and thus 

 showing by the temporary excess of current in this cross communication, the tempo- 

 rary retardation in the circuit A B D. 



1104. On adjusting a platina wire at x (1081.) so that it should not be ignited by 

 the current passing through it whilst contact at G and E was continued, and yet be- 

 come red hot by a current somewhat more powerful, I was readily able to produce 

 its ignition upon making contact, and again upon breaking contact. Thus the momen- 

 tary retardation in A B D on making contact was again shown by this result, as well 

 also as the opposite result upon breaking contact. The two ignitions of the wire at x 

 were of course produced by electric currents moving in opposite directions. 



1105. Using the helix only, I could not obtain distinct deflections at x, due to the 

 extra effect on making contact, for the reasons already mentioned (1088.). By using 

 a very fine platina wire there (1083.), I did succeed in obtaining the igniting effect 

 for making contact in the same manner, though by no means to the same degree, as 

 with the electro-magnet (1104.). 



1106. We may also consider and estimate the efffect on making contact, by trans- 

 ferring the force of induction from the wire carrying the original current to a lateral 

 wire, as in the cases described (1090.) ; and we then are sure, both by the chemi- 

 cal and galvanometrical results (1091.), that the forces upon making and breaking 

 contact, like action and reaction, are equal in their strength but contrary in their 

 direction. If, therefore, the effect on making contact resolves itself into a mere re- 

 tardation of the current at the first moment of its existence, it must be, in its degree, 

 equivalent to the high exaltation of that same current at the moment contact is broken. 



1107. Thus the case, under the circumstances, is, that the intensity and quantity 

 of electricity moving in a current are smaller when the current commences or is 

 increased, and greater when it diminishes or ceases, than they would be if the in- 

 ductive action occurring at these moments did not take place; or than they are in the 

 original current wire if the inductive action be transferred from that wire to a colla- 

 teral one (1090.). 



1108. From the facility of transference to neighbouring wires, and from the effbcts 

 generally, the inductive forces appear to be lateral, i. e. exerted in a direction per- 

 pendicular to the direction of the originating and produced currents : and they also 



