DOVE ON THE ELECTRICITY OF INDUCTION. 1/3 



like connexion in which the secondary current does not compen- 

 sate itself. It follows, from the united results detailed at 72) and 

 75), that the incipient extra current is increased by the same 

 means in its negative action, as is the final extra current in its 

 positive action, and that in both cases bundles of wire exert a 

 more powerful physiological action than solid iron. 



76. In the fourth section the remarkable phcenomenon has 

 been discussed, that the physiological action of the secondary 

 current of the Leyden jar is weakened by the insertion of 

 solid iron into the connecting spiral, and increased on the con- 

 trary by the insertion of bundles of iron wire. This was ex- 

 plained in the following manner:— The phaenomena produced 

 simultaneously in iron by the action of the connecting wix*e, 

 namely, magnetic polarity and electric currents, act here in 

 such a manner that the retai'ding influence of the electric cur- 

 rents overpowers the increasing action of the magnetic pola- 

 rity, and hence the final result with solid iron has a weakening 

 tendency, whilst with more lasting currents, e. g. the galvanic 

 current, in which the magnetism has time to develope itself, its 

 action overpowers that of the electric currents, and hence an 

 augmenting action also results from solid iron. This view, 

 that the secondary current of the Leyden jar is only different 

 from other induced currents in consequence of the shortness of 

 the primary current producing it, which want of duration is 

 without effect upon the electric currents induced in iron, but 

 prevents the complete development of its magnetism, gains in 

 probability, if it can be shown that the same phaenomenon may 

 be produced by other means than frictional electricity ; now this 

 can be done in the following manner : 



77' If the extra spiral is surrounded with a secondary spiral, 

 its physiological action will be diminished, as we have seen at 73). 

 The surface of a solid iron cylinder exerts the same influence 

 as a secondary spiral. An increase in the length of wire of the 

 extra spiral weakens the primary current. If the number of 

 inserted extra spirals is augmented, and a solid iron cylinder 

 placed within each, then the primary current weakened by the 

 lengthening of the wii-e will only be capable of exciting a slight 

 degree of magnetism in these iron cylinders. If the intensity of 

 the electric currents excited by the coils of the extra spiral on 

 the surface of the iron cylinder does not diminish in the same but 

 in a less degree than the magnetism simultaneously excited in the 



