Was Benjamin Franklin wrong (about conventional current)?
Electric current, A.K.A, "conventional current", is an abstract current, the flow of electric charge.  From a previous answer I gave here:


  Electric current is an abstract current, the flow of electric charge, not a physical current like, say, electron current, the flow of electrons.
  
  But electric charge is a property of things, not a thing, i.e.,
  electric charge is always "carried" by a thing.  
  
  So, while an electron current is necessarily an electric current (due
  the negative electric charge carried by the electron), an electric
  current is not necessarily an electron current.
  
  For example, in a salt solution, we have two species of electrically
  charged ions present,  the positively charged sodium ion and the
  negatively charged clorine ion.  Imagine that the sodium ions are
  moving to the right and the chlorine ions are moving to the left.
  
  Obviously, we have two ion currents in opposite directions but there
  is just one electric current and it must have a direction.  The
  direction of electric current is, by convention, the direction of the
  flow of positive charge.
  
  So, in this case, both ion currents contribute to an electric current
  to the right.  The first term is due to the positive ions to the
  right.  The second term is due to the negative ions to the left where
  the negative sign numerically "flips" the contribution to the
  electric current.
  
  Think about it this way, if I told you that I was travelling at -60mph
  west, you'd know that I was actually going 60mph east.  Similarly, a
  negative charge current leftward is an electric current rightward.