1883.] Theory of Magnetism based on New Researches. 183 



The exterior diameter of the coil D is 5 J centims., and that of the 

 interior vacant aperture 3-J centims., the width is 2 centims. Upon 

 this coil is wound 200 metres of No. 28 silk-covered copper wire. A 

 compensating coil E, whose wires are (when at zero) perpendicular to 

 the coil D, can be rotated upon its axle F by means of its index lever 

 arm Gr, moving over a graduated circle not shown in the diagram 

 The two coils D and E are affixed to the same piece of board, but 

 independent of the board upon which rest the abutments A' A", so 



