In England in 1947, Cecil Powell and Giuseppe Occhialini used the same method as Chowdhuri, but with better emulsions, to demonstrate the existence of the pion. A few years earlier, in fact, from 1939 to 1942, in Kolkata, India, scientist Bibha Chowdhuri, together with director Debendra Mohan Bose of the Bose Institute, had experimentally observed and published reports on showers of mesotrons, later called mesons. They had studied batches of Ilford halftone plates exposed to cosmic rays at two different altitudes, one in Darjeeling and a higher one in Sandakphu. The particles had decreased in mass at lower altitudes, suggesting that they had decayed over time. They had also noted that the decays were curved, likely due to multiple scattering of the particles. They had been unable to continue their investigation because more sensitive emulsion plates were not available.
