Action of a Galvanic Coil on an external small Magnet, 433 



pressure. In an analogous manner the stress necessary for the 

 maintenance of the motion in any element of a galvanic current 

 is capable of operating in all directions, but produces no motion 

 unless the means of circulating be provided. Such provision is 

 made when another complete current is placed in the neigh- 

 bourhood of the first; and on this principle mutual action, 

 depending on the coexistence of the motions, may take place 

 between each element of one rheophore and all the elements of 

 the others. These views being adopted, the motions of either 

 of two rheophores resulting from this composite action of their 

 currents may be determined by the following considerations. 

 [I take occasion to remark that in ' The Principles of Physics/ 

 p. 601, galvanic induction is attributed to the sudden action of 

 a state of stress like that supposed above.] 



59. First, as was remarked in art. 58, the above-mentioned 

 stress admits, for the same reason as hydrostatic pressure, of 

 being resolved in rectangular directions ; but inasmuch as it is 

 so intimately related to a galvanic current that the one does not 

 exist without the other, the resolution must take place within 

 the compass of each element of the rheophore, and so as to give 

 rise to elementary galvanic currents of the ascertained type. 

 It is next to be considered that, according to the reasoning 

 contained in arts. 55 and 56, the action of one rheophore 

 tends to produce motion of translation of the other only when 

 a current pertaining to the former flows within the superficial 

 boundary of the other in a direction parallel to its axis, and 

 varies from point to point in the directions perpendicular to the 

 axis in such manner that the resulting accelerative force acts in 

 the same directions. Reserving at present a more general 

 application of these principles, I propose now to apply them in 

 the solution of the problem of the action of a sinuous current. 



60. Taking the experiment, at first, as made by Ampere, the 

 sinuous rheophore and the straight return one in the mean 

 direction of the other will be supposed to be rigidly connected 

 and fixed, and to act upon a movable one parallel to the latter. 

 If, in conformity with the principles above laid down, each 

 element of the sinuous current be resolved in directions parallel 

 and transverse to the mean direction, the sum of the latter re- 

 solved parts will have no translatory effect on the movable 

 rheophore, because they are wholly in directions transverse to its 

 axis. The other resolved parts will tend to move the rheophore 

 in the manner described in arts. 55 and 56 ; and as their sum 

 is just equal to the return current but opposite in direction, 

 they will have the effect of neutralizing the translatory action 

 of that current, so that no motion of the movable rheophore 

 will ensue. 



Phil. Mag. S. 4. Vol. 48. No. 320, Dec, 1874. 2 F 



