OF ELECTRO-DYNAMIC FORCES. 499 



react upon each other, upon the relative position and distance 

 of these \vires. 



For this purpose the arrangement Avas effected in such a 

 manner, that one conducting wire, i. e. the multiplier, could be 

 placed in any position as regards the other, i. e. as regards the 

 bifilarly-suspended coil, the latter forming the larger coil, which 

 inclosed the former smaller one. 



Both coils were always placed in such a position that their 

 axes Avere in the same horizontal plane, and formed a right 

 angle with each other. 



The distance of the two coils was determined by the distance 

 of their centres from each other, and was thus assumed as = 

 Avhen the centres of the two coils coincided. 



When the latter was not the case, in addition to the magnitude 

 of the distance of the two centres, it was also requisite to measure 

 the angle which the line uniting the two central points formed 

 with the axis of the bifilarly-suspended coil, whereby the direc- 

 tion in which the centre of the multiplier was removed from 

 the centre of the bifilarly-suspended coil was defined. For this 

 purpose the four cardinal directions were selected at which the 

 former angle had the value 0°, 90°, 180° and 27U°, i. e. when the 

 axis of the bifilarly-suspended coil, like the axis of the needle 

 of a magnet, was arranged in the magnetic meridian, the centre 

 of the multiplier was removed from the centre of the above coil, 

 sometimes in the direction of the meridian, north or south, and 

 sometimes in the direction at right angles to the magnetic meri- 

 dian, east or west. In each of these different directions the mul- 

 tiplier was placed successively at different distances from the 

 suspended coil. 



This arrangement of different positions and distances of the 

 two conducting wires of the dynamometer accurately corre- 

 sponds, as is seen at a glance, to the arrangement of differ- 

 ent positions and distances of the two magnets, upon which 

 Gauss based his measurements, in demonstrating the funda- 

 mentil principle of magnetism. The bifilarly-suspended coil 

 here occupied the place of Gauss's magnetic needle and the 

 multiplier the place of Gauss's deflection-rod. The only im- 

 portant difference is, that the mutual action of the magnets 

 could only be observed from a distance; consequently in the 

 magnetic observations that case was excluded in which the cen- 

 tres of the two magnets coincided ; whilst in the electro-dynamic 

 measurements of which we arc now speaking, the system could 



