"In 1923 ... was investigating s... using a . ...The ...rays would knock electrons out of atoms... whose trails he could see... [I]n addition to knocking electrons out of the gas, they were ejecting them out of the walls of the chamber ...which interfered with the measurements... He... came up with the... idea of sweeping away the unwanted electrons by putting the chamber between the poles of a large magnet. ...[T]he clearer view revealed ...the magnetic forces seemed to make some of the 'electrons' curve 'the wrong way'. Today we know he was seeing s, but... [the] anomalous trails were a distraction from what he was trying to do. ...News about these images spread ...and five years later Skobeltsyn decided to show them at an international conference in Cambridge. ...[N]o one could offer an explanation. It was ironic that [this was]... the same year and... place that Dirac came up with his theoretical prediction of positrons... [A]s no one at the time had any reason to expect... positrons existed, he missed the big prize."