226 GREAT MEN OF SCIENCE 



whereby their well-known opposite effects were neutralised 

 by their union, the electric current must have appeared as 

 something fairly complicated and indefinite. The idea of it 

 in any case became indefinite, from the fact that the simul- 

 taneous 'current' of two electricities, obviously had no de- 

 fined direction. In accordance with this, Oersted did not 

 speak of an electric current at all, but used the expression 

 'electric conflict'^ for the process in the wire, and this in- 

 definite terminology also corresponds to the confusion 

 shown in the then rapidly accumulating publications relat- 

 ing to continuations of Oersted's experiment. 



As opposed to this. Ampere decides in the same year, 

 1820, that he will call the whole process in the discharge wire 

 an electric current, whereby no regard will be paid to details 

 (which, by the way, are not too well understood even 

 to-day), and that the direction of the current is to be defined 

 as the direction in which we imagine the positive electricity to 

 move. This made the electric current something definite: 

 a special natural process, the observable peculiarities of which 

 are offered as a subject for investigation undisturbed by 

 difficulties in thought, which could not for the moment be 

 overcome. A new and well-defined concept had been 

 formed, and clear concepts, correctly adapted to nature, 

 have ever been the guiding stars of progress in knowledge. 

 In Volta's pile or cup apparatus, this current circulates in a 

 definite direction along the closed conducting circuit, as, by 

 the way, Volta himself also expressly states. 



Ampere also distinguished sharply for the first time be- 

 tween the phenomena of electric tension and those of electric 

 current. Phenomena of tension had long been known from 

 static electricity; they appeared in the pile before the con- 

 ducting circuit was closed, and they could be followed by 



1 The title of Oersted's Latin publication of his discovery in the year 

 1820 read Experimenta circa effeclum conflictus electrici in acum 

 magneticam. 



