Alan Cox and Emily Barber talk about their roles in “Cornelius,” a forgotten masterpiece from one of Britain's greatest dramatists, J. B. Priestley. As bankruptcy looms, the ever-optimistic Jim Cornelius, partner at import firm Briggs and Murrison, is fighting to keep his creditors happy and his spirits up. Tensions rise with the arrival of Judy, the beautiful, young typist who shows Cornelius the life he could have led. “Cornelius” is playing at 59E59 theater.