Prof. E. Bouty's Studies on Magnetism. 



95 



Therefore, conformably to the observations we have previously 

 given, the extra current proceeding from P is sensible in Q, that 

 from Q in P, but the magnetic effect of each is nil in the coil 

 from which it emanates. 



If the coils P and Q are placed as derivations with respect to 

 one another, the direct extra current of each coil traverses the 

 other in a direction contrary to the current from the pile. In 

 this case experiment shows that the interruptions occasion a di- 

 minution of the magnetic moment, and the establishments an 

 augmentation, as might have been foreseen from what precedes. 



III. The circuit comprises a coil and a condenser. 



This case is realized with a Ruhmkorff coil in the following 

 manner : the condenser C (fig. 4) is fixed in a derivation desti- 

 tute of resistance, on which the interruptions are practised. 

 The coil B may also be placed in the derivation, and the inter- 

 ruption be produced in a point of the principal circuit (fig. 5). 



Fig. 4. 



Fig. 5. 



In each of these arrangements the condenser forms with the 

 coil a closed circuit apart from the interruption, either directly 

 or by the intermediation of the pile. It would not be the same 

 if the interruption were made in the principal circuit with the 

 arrangement of fig. 4, or in the derivation in the case of fig. 5 : 

 these last two arrangements are useless, as experiment has 

 shown ; but if one of the former be employed, the rupture of 

 the circuit is observed to produce a diminution of the magnetic 

 moment of the needles magnetized by being passed to the coil. 

 The effect observed cannot be attributed to the extra currents 

 of the condenser ; for these act in a direction contrary to the 

 result obtained. The condenser employed * behaves, with respect 

 to the production of extra currents, like a coil of negligible 

 power. 



* That of a Ruhmkorff coil, of which the explosion-distance is 3 centims. 



