At the end of 1857, Orsini briefly visited England, where he contacted gunsmith Joseph Taylor and asked him to make six copies of a bomb of Orsini's own design; it would explode on impact and used fulminate of mercury as an explosive. The bomb was tested in Sheffield and Devon with the aid of French radical Simon Bernard. Satisfied, Orsini returned to Paris with the bombs and contacted other conspirators, Giuseppe Pieri, Antonio Gomez and Carlo di Rudio (later changed to Charles DeRudio).