L.M.P.11. (old departmental catalogue number in aluminium paint, removed). DES after THOMSON,Joseph,John,Sir. 1897 [Cavedish Laboratories, Trinity College, Cambridge] [England] MANU Unsigned. [first quarter 20th century] DES after PERRIN,Jean,Baptiste,Professor. 1895 Ecole Normale Superieur, Paris, France This apparatus is an adaptation of a design originally by Jean Baptiste Perrin. It is now more commonly known as a Thomson tube. It was adapted by J.J. Thomson for an experiment to calculate the charge on the particles making up cathode rays, which were called corpusles by Thomson. He discovered that the charge was equal to the charge of an hydrogen ion in electrolysis and hence that there was a particle smaller than the hydrogen atom. We know Thomson's corpucles as electrons. This version has a Braun fluorescent screen added to enhance the spot of light created by the electrons in order that students could observe the phenomenon.
The glass fluoresces lime green under ultra violet light.