Eugen Goldstein was a German physicist at the turn of the century. It could be argued that he was the first person to discover the proton. The discovery of the proton is officially credited to Ernest Rutherford in 1920. But Goldstein had discovered anode rays (he called them canal rays) which are like cathode rays but of the opposite charge (positive instead of negative). These are emissions of nuclear subatomic particles emitted from gasses exposed to an electric charge. Depending on the gas being used, the particles can be composed of any number of protons. But when he worked with hydrogen, because its nucleus only contains one proton, he was the first person to isolate a proton though he did not know that he had isolated a single subatomic particle at the time.