110 HISTORY OF GALVANISM. 



motion is stopped ; and at that instant, an impulse 

 is produced in the direction of the motion. Now 

 this description applies alike to mechanical impact, 

 and to electrodynamical induction. 



I should, therefore, conceive that no more gene- 

 ral or appropriate term can be found to describe 

 the phenomena here spoken of, than electrodynamic 

 reaction. Our conception of the mechanical pro- 

 perties of the electric fluid is necessarily, as yet, 

 somewhat obscure; and we know very imperfectly 

 the manner in which an electric current sets a 

 neighbouring one in motion. Yet I think it cannot 

 be doubted that the same beautiful theory of Am- 

 pere, which explains so well all the laws of electro- 

 dynamical action, not only admits, but requires, 

 that, if induction in such cases do exist, it shall be 

 accompanied with a reaction, following laws like 

 those which Mr. Faraday has unravelled with such 

 exquisite skill. But Mr. Faraday himself does not 

 appear to admit this view. " The first thought that 

 arises in the mind is," he says 14 , "that the electricity 

 circulates with something like momentum or inertia 

 in the wire, and that thus a long wire produces 

 effects at the instant the current is stopped, which 

 a short wire cannot produce. Such an explanation 

 is, however, at once set aside by the fact, that the 

 same length of wire produces the effects in very dif- 

 ferent degrees, according as it is simply extended, 

 or made into a helix, or forms the circuit of an 



" Art, 1077- 



