184 DOVE ox THE ELECTRICITY OF INDUCTION. 



and I. The current proceeded from I to III, in the figure 

 therefore from s to a. 



2. Galvanometer between 8) and 4). First it forms a se- 

 condary, then a chief connexion. The keeper as well as the ex- 

 tra spiral remain in the connexion. The current is from I to II, 

 in the figure therefore also from s to a. 



3. Galvanometer between 4) and 15). At the break the 

 keeper leaves the connexion, whilst the voltameter with the extra 

 spiral come into the connexion. The current proceeds from 13) 

 to 4). This corresponds in the drawing Avith III to II. Here 

 too therefore the current is in the direction from s to a. 



It was further ascertained, that with forked springs the con- 

 stant direction of the current, determined by the galvanome- 

 ter immediately included in the circuit, is the same with an in- 

 serted spiral as without it, therefore /) is in a like direction with 

 p-A + E. 



5. Experiments with the empty wire keeper. 



90. Although it is probable a priori that primary currents, 

 which are excited by the magnetization of soft iron, are identical 

 in their action with currents which are induced by a magnet in 

 motion, it appeared nevertheless desirable to prove this empiri- 

 cally. Instead of the iron keeper surrounded with wire, the 

 empty keeper described at § 40 was employed. The insertion 

 of the spiral, even without a nucleus of iron, produced with this 

 hollow wire keeper exactly the same modifications in the phy- 

 siological action as those described with the iron keeper at § 72. 

 The result is important, because it upsets the opinion that the 

 presence of iron is essential in causing A to overpower E, and 

 because it will now be seen that we were justified in having 

 neglected in the foregoing researches the reaction of the extra 

 current upon the magnetism of the rotating keeper. Nor has 

 the form of the iron exerting the inducing action any influence, 

 for the same phaenomena are obtained when the keeper of the 

 machine is composed of bundles of iron wires. 



6. Immediate production of sparks on interrupting conduction. 



91. Lastly, a phsenomenon observed during the researches 

 with Saxton's machine deserves a short notice, because it affords 

 means for answering the question, whether the spark observed 



