Cavendish Laboratory : Pollard and Constable counting particles in 1929-30

Cavendish Laboratory

<p style='text-align: justify;'>In 1929, the scintillation method of counting particles was replaced by an ionization chamber connected through a valve amplifier to an Einthoven galvanometer. The deflections were recorded on a photographic film. In preliminary investigations and in cases where no permanent record of the protons was required, the galvanometer was replaced by headphones. The output was sufficient to operate several sets of headphones in parallel, so that two or more observers could count the clicks simultaneously (https://doi.org/10.1098/rspa.1931.0017).</p>