DOVE ON THE ELECTRICITY OF INDUCTION. 137 



condenser*, and also a physiological test, to which I was led in 

 the course of the experiments. The following are the results. 



1. Physiological mid electroscopical effects of the induced current. 



44. The physiological action of the current induced in the 

 secondary wire by the connecting wire of the battery is dimi- 

 nished by all unmagnetic metals, and so much the more the bet- 

 ter the metal conducts. This decrease of power is therefore 

 much less with antimony, bismuth and lead, than with copper 

 and brass. With previously compensated spirals, the shock ob- 

 tained is therefore so much the more powerful the better the 

 metal conducts which is placed in one of them. The current 

 tested by the condenser and by the resinous figures proceeds 

 from the empty spiral ; the resulting shock is therefore caused 

 by the weakening influence of the metal upon the spiral in which 

 it is inserted. 



45. If, instead of a solid metallic cylinder or a metallic 

 tube, a cardboard tube surrounded with a spiral wire made of 

 copper and covered with silk is inserted into one of the connecting 

 spirals, the equilibrium of the current remains unimpaired in the 

 secondary spirals when their ends are not joined, but it is de- 

 stroyed when their ends are connected. A spiral formed of a 

 once doubled wire, which may be considered to consist of two 

 like spirals united in an opposing direction, does not destroy, 

 when the ends are joined, the equilibrium of the current in the 

 secondary spirals : the effect of the first wire must therefore be 

 attributed to an electrical current excited in it, the inactivity 

 of the second to the mutual neutralization of the destructive influ- 

 ence by two equal electrical currents. 



46. Such electrical currents must also exist in solid cvlin- 

 ders and entire tubes; for the effect of the former is diminished by 

 a longitudinal division, i. e. by the conversion of the brass cyhn- 

 der into a bundle of well-insulated brass wires : the effect of the 

 latter is also weakened by a longitudinal section. Bundles of 

 brass wires exert a less obstructive action than an entire tube of 



* These and a few otlicrs of the following experiments I instituted in com- 

 mon with M. Riess, who permitted me to make use of his apparatus for that 

 purpose. The mudus of proceeding proposed by Pacinotti and Joule by means 

 of a perforated card, and tlic passing of a spariv with the wire ends projecting 

 over each other, were made known at a later period. 



