180 DOVE ON THE ELECTRICITY OF INDUCTION. 



arm of the spring is in metallic connexion with one cylinder, and 

 each stand consequently only in metallic connexion with one cy- 

 linder. If, on the contrary, the voltameter is inserted between 

 the wires I and III, the connexion then proceeds from the 

 stand D through the extra spiral to the stand E, and from this 

 to the voltameter. In the first case the resistance to conduction 

 would consist of the resistance offered by the wire surrounding 

 the keeper, and that of the fluid between the electrodes of the 

 voltameter. By the addition of the usual exti-a spiral the first 

 part of this resistance is increased about five times. Neverthe- 

 less the whole amount of gas thus obtained was only about one- 

 fifth of that obtained without the extra spiral, and the quantity 

 was very much more lessened by the insertion of iron in the form 

 of rods or bundles of wires. If the quantity of gas obtained is 

 taken as the measure of the quantity of electricity which has 

 passed through the wire in a certain time, then this is actually 

 diminished by the action of the revolutions of the extra spiral 

 upon each other, and by the magnetism of the iron which it 

 encloses. 



When the usual springs 3), 5), 9) are used instead of the 

 forked springs y y, but in such a manner that 3) also is in con- 

 stant metallic contact with the cylinder w^.j, and the voltameter is 

 interposed in the first instance without this spiral, and immedi- 

 ately in its stead between 1) and 6), afterwards in conjunction with 

 this spiral so that it may be supposed to occupy a position in 

 the middle of the inducing wire S, then with alternating cun'ents 

 analogous phaenomena are obtained to those which have been 

 observed with currents in a like direction. 



85. If however the voltameter is to form a secondary con- 

 nexion with uninterrupted currents, at one time to the keeper, 

 at another to the extra spiral, then it must be interposed, the 

 springs 3), 5), and 9) preserving a like position, at one time 

 between I and III and then between II and III. In both cases 

 the insertion of iron considerably accelerates the decomposition 

 of water. The current therefore which divides itself between 

 the primary and secondary connexion, experiences, when iron is 

 present in the extra spiral, as well in the coils of this spiral as 

 also in the coils of the wire surrounding the keeper, a greater 

 amount of resistance than when the extra spiral contains no 

 iron. If, on the contrary, the voltameter form a secondary 

 connexion to the straight portion of the principal connexion. 



