16mm Camera for Recording Movement of Electroscope Fibers (1930s)
These unusual looking devices are 16mm movie cameras designed and built by Hugh Carmichael at the Cavendish Laboratory, ca. 1934.
The lens of the camera was focused on the fiber of an electroscope connected to a large ionization chamber. Cosmic ray interactions in the chamber would cause a sudden deflection of the fiber and this deflection was recorded on the slowly advancing (0.1 mm/sec) film. The filming not only facilitated investigation of these relatively infrequent events, it also permitted a mathematical analysis that would give the size of an off-scale deflection.