1884.] on Volta-Electric and Magneto-Electric Induction. 



being absolutely correct, the 

 experiments having been 

 somewhat hurriedly made, 

 and merely given with the 

 view of enabling you to 

 understand the results of 

 carefully-made experiments 

 with various metals. These 

 results are graphically 

 shown on the large sheet 

 suspended before you, 

 marked 2 ; and, as the 

 measurements are to scale, 

 they can be compared 

 directly with each other. 

 The large circles represent 

 the revolving discs, the 

 small ones show the position 

 of the poles of the electro- 

 magnet, and the arrows the 

 direction of rotation. The 

 coloured portions show the 

 electro - motive force at 

 every point round the re- 

 volving disc ; thus in every 

 case the strongest point is, 

 as might be expected, 

 directly in front of the 

 poles of the exciting mag- 

 net, the strength gradually 

 fading from thence on either 

 side. The blue portions 

 show the excess of inductive 

 effect there produced, rela- 

 tively to a point equidistant 

 from the magnetic poles, but 

 on the opposite side. If the 

 current set up in the metal 

 simply depended upon the 

 intensity of that part of 

 the magnetic field through 

 which the metal was passing, 

 then equidistant points on 

 either side of the magnetic 

 poles should produce equal 

 deflections, because the 

 magnetic intensity is equal ; 

 on inspecting the diagrams, 



127 



