a New Form of Earth Inductor. 



581 



ballistic deflexion, S z , on the galvanometer noted. The 

 actual distance moved through was 15*1 cm. The de- 

 flexion was proportional to the flux cut, which was equal to 

 Z, the vertical component of the Earth's field, multiplied by 

 the area, A, described by the slider. 



Fisr. 2. 



=i s. 



To determine to what change of flux this deflexion of the 

 galvanometer corresponded, the slider SiS 2 was removed, the 

 tube circuit closed at a, and the ballistic deflexion Bi of the 

 galvanometer observed when a current of two amperes was 

 made or broken in the wire circuit. The value of the current 

 in the wire circuit was given by the ammeter A], which had 

 been previously calibrated, and by means of which its value 

 could be determined to within one per cent. If the self- 

 inductance, L, of the square of brass tubing is known, the 



