292 Researches in the Theory and Calculus of Operations. 



of the currents of elective force. At each extremity A and 

 A' a resisting medium is encountered, and reaction takes 

 place towards the centre 0, constituting the return dis- 

 charge. If instead of actual contact of the bodies holding 

 the interfering forces, a dielectric be placed between them 

 at 0, the effect is electrization by influence (Faraday). 



If now the series A' be turned into the reverse position 

 (fig. 26), and then connected with A by the dielectric C 

 (which may even be a moderately thin stratum of common 

 air), while the current in A is from right to left, that in A' 

 is from left to right as it ought to be. If the current in A is 

 infinite in A and finite in A', the atomic forces in the latter 

 will be held in their present position by the continuous 

 pressure of A ; but if the pressing current in A be stopped, 

 or the dielectric withdrawn, reaction occurs from A' to C, 

 restoring the former state of equilibrium (phenomena of 

 induction, Henry). 



28. Let AA X (fig. 27) represent an axial section of a cylin- 

 der, made of non-conducting material (glass, wood, or card- 

 paper), around which is coiled a copper wire wound with 

 silk or insulated with resin, etc., and ready to be charged 

 with electricity from the galvanic jar P. CCj is a core of 

 soft iron, placed and retained in the centre of the cylinder. 

 As in all cases and in all situations, emanation of force is 

 constantly going on from the centre of any body whatever, 

 reaching the surface and there encountering a resisting 

 medium; so in the case of the present core of iron rods CC^, 

 the largest amount of spherically emanating force will ap- 

 pear at the extremities and b'b^ where, while the 

 cylindrical coil AA X remains uncharged, a portion of each 

 is destroyed by the forces of the resisting medium, consist- 

 ing say of the atmosphere surrounding the core and the 

 cylinder; and although there is a constant transmission of 

 remaining force from the core tor the wire, this is equili- 

 brated by the reacting emanation from the wire. But when 



