Following the 1896 discovery of radioactivity by Henri Becquerel using photographic emulsion, Ernest Rutherford, working first at McGill University in Canada, then at the University of Manchester in England, was one of the first physicists to use that method to study in detail the radiation emitted by radioactive materials. In 1905 he was using commercially available photographic plates to continue his research into the properties of the recently discovered alpha rays produced in the radioactive decay of some atomic nuclei. This involved analysing the darkening of photographic plates caused by irradiation with the alpha rays. This darkening was enabled by the interaction of the many charged alpha particles, making up the rays, with silver halide grains in the photographic emulsion that were made visible by photographic development. Rutherford encouraged his research colleague at Manchester, Kinoshita Suekiti, to investigate in more detail the photographic action of the alpha-particles.