Cloud Chamber Photograph Positron Lead plate Larger curvature Carl Anderson of particle 1905-1991 above plate MARC1H15,1923 PHYSICAL REVIEW VOLUME 43 means it's moving slower (lost energy as it The Positive Electron CARL D.ANDERSON,Californie Institule of Tecknology,Pasudend,California passed through) (Received February 28,1933) Out of a group of 1300 photographs of cosmic-ray tracks curvatures and ionizations produced require the mass to be in a vertical Wilson chamber 15 tracks were of positive less than twenty times the electron mass.These particles particles which could not have a mass as great as that of will be called positrons.Because they occur in groups the proton.From an examination of the energy-loes and associated with other tracks it is concluded that they must ionization produced it is coneluded that the charge is less be secondary particles ejected from atomie nuclei. than twice,and is probably exactly equal to,that of the Editor proton.If these particles carry unit positive charge the N Auguot名1932，during the coureof eleetrons happened to produce two tracko co photographing cosmic-ray tracks produced placed as to give the impression of a single in a vertical Wilson chamber (magnetic field of particle shooting through the lead plate.This