DOVE ON THE ELECTRICITY OF INDUCTION. 177 



cent at the moment connexion is broken, the presence of the iron 

 A will augment the action more than E, and the sparks will con- 

 sequently be diminished*. Now this occurs in so remarkable 

 a manner, that on the insertion of iron cylinders into the spiral 

 the brilliant spark which was previously observed at the point of 

 interruption u on the cylinder w^ almost completely vanishes. 

 That this diminution of the spark is caused by an extra current 

 produced by the spiral is evident; for if II and III are connected 

 by metal, the spark on breaking connexion at u reassumes its 

 full splendour, whilst with the connexions I and II and I and 

 III every spark at u is naturally prevented. If, lastly, the extra 

 spiral is inserted into a secondary spiral, the spark at u is very 

 much increased by its connexion. 



81. As it has been shown at (78) that an obvious diminution of 

 the shocks was only perceived with solid iron rods where bun- 

 dles of wires exhibited an indisputable augmentation, so is the 

 diminution of the spark much more considerable when solid 

 iron rods are inserted than when the same mass of iron in the 

 form of insulated bundles of wires is used, and still more marked 

 when the bundle of wires is enclosed in a conducting case (a brass 

 tube) than when unenclosed. Everything that favours an aug- 

 mentation of the extra currents tends to postpone, as regards 

 time, the maxima of their intensity. By the same means also 

 the action of the incipient extra current is increased, that of the 

 final extra current on the contrary diminished. The insertion 



* Many observations render it exceedingly probable that a galvanic cur- 

 rent, by means of which iron is magnetized, attains the maximum of its intensity 

 earlier than the iron attains the maximum of its magnetic polarity. It is there- 

 fore not impossible that, if the electric current is interrupted during the time 

 that the magnetism is on the increase in the iron, the magnetic intensity should 

 continue to increase for a short time after the interruption of the electric cur- 

 rent. If we regard magnetization, in conformity with the theory of Ampere, 

 as an influence directing the electric currents already existing and surrounding 

 the individual molecules, then it would amount to this, that the elementary cur- 

 rents which are actually circulating in a rotatory maimer do not immediately 

 resume their original state the moment the motive power ceases, but continue to 

 move ill the direction which has been given to them for a short space of time. 

 According to the view of Coulomb, elementary magnets would have to be sub- 

 stituted for elementary currents. Now as long as the magnetism increases, A 

 is induced in the connecting wire and not E. 'i'he occurrence of E is therefore 

 still further postponed by the presence of the iron, and consequently the dura- 

 tion of the discharge altogether increased. All these phsenoniena however will 

 not occur when the primary current has already continued for such a length 

 of time, that it itself, as well as the magnetism produced by it, have already at- 

 tained their maxima before the interruption, and have consequently become 

 stationary. 



