326 Mr. K. IE. Hall on the new Action of 



manont Change in the equipotential lines after the electromag- 

 net had ceased to act. 



It is perhaps idle to speculate as to the exact manner in 

 which the action between the magnet and the current takes 

 place in any of the preceding experiments ; but it may be 

 worth while to remark a seeming analogy, somewhat strained 

 perhaps, between this action and a familiar mechanical phe- 

 nomenon,, the theory of which has of late attracted consider- 

 able attention. It is well known that a base-ball projected 

 swiftly through the air, and having at the same time a rapid 

 motion of rotation about its vertical axis, does not throughout 

 its course continue in the original vertical plane of its motion, 

 but follows a path curving sensibly to one side. Imagine now 

 an electrical current to consist of particles analogous to the 

 base-ball moving through a metallic conductor, the electrical 

 resistance of which will correspond to the mechanical resist- 

 ance offered by the air. Suppose, further, the particles of 

 electricity, on coming within the influence of the magnet, to 

 acquire a motion of rotation about an axis parallel to the axis 

 of the magnet *. Under all these supposed conditions we might 

 perhaps expect to find the action which is actually detected. 

 To account for the reversal of the action in iron we might 

 suppose the particles of electricity to acquire in this metal a 

 rotation about the same axis as in the other metals, but in the 

 opposite direction. Even after all these generous concessions 

 in favour of our hypothesis, however, it fails to account for the 

 behaviour of nickel as different from that of iron. The ana- 

 logy, such as it is, which has been pointed out, is perhaps 

 curious rather than significant. 



Historical. 



I am not aware that investigators during the first part of 

 the century made any attempt to discover the phenomenon 

 which has been the subject of the observations described in the 

 preceding article. Wiedemann t, however, mentions two in- 

 vestigators who have at different times given the subject their 

 attention. The first of these in point of time was Feilitzsch J. 

 He made use of two flat spirals of wire, through each of which 

 an electric current was made to pass. These currents, passing 



* Maxwell (' Electricity and Magnetism,' vol. ii. p. 416) says : — "I think 

 we have good evidence for the opinion that some phenomenon of rotation 

 i3 going on in the magnetic field, that this rotation is performed by a 

 great number of very small portions of matter, each rotating on its own 

 axis, this axis being parallel to the direction of the magnetic force," &c. 



t Galvarrismus, vol. ii, p. 174. 



X Berichte der Naturforscher in Karlsruhe, 1858, p. 151 &c. 



