ON THE VARIABLE STATE OF ELECTRIC CURRENTS. By Professor 

 BLASERNA, of the Royal University, Rome. 



Gentlemen, 



I regret much not being able to address you in English, and 

 I must therefore ask your indulgence for speaking to you in a language 

 which is neither yours nor mine. 



The question of the Variable State of Currents was originated and 

 has been treated by Ohm. 



By following up the ideas which lead him to the discovery of one of 

 the most important laws of physical science, he arrived at the con- 

 clusion, with regard to the origin of the current, that the fixed normal 

 state, from which the current derives its permanent intensity, is pre- 

 ceded by a variable state, in which, from the moment of interruption, 

 begins at zero, and reaches, in a very short space of time, its permanent 

 intensity. 



Ohm endeavoured also to establish the law of this movement, which 

 may be represented by a curve, at first convex, and then concave 

 towards the axel of the abscisses, and which has consequently a point 

 of inflexion. 



We can understand that the variable state should exist. There are 

 no phenomena in Nature which do not require a certain time for their 

 formation and development, and the question is merely to find out 

 whether this time is sufficiently long to be indicated or measured by 

 instruments of the most delicate make, and the most perfectly adapted 

 for the object to which they are to be applied. 



Faraday's great discoveries of inducted currents and extra currents 

 gave to this question a new and wider aspect. The question may be 

 asked, What are the nature and duration of the extra current ? either of 

 cessation or interruption ; and as the extra current is nothing but the 

 current inducted on itself, the general laws of inducted currents may 

 be looked for in wires and in fixed helices. 



These different questions have been discussed by a great number Of 

 scientific men. I will mention, among others, M. Helmholtz, who, by 

 calculations and by experiments, has succeeded in representing the 



