Editing Cathode ray (section)

===Negative electric charge===
[[Jean-Baptiste Perrin]] wanted to determine whether the cathode rays actually carried negative [[Electric charge|charge]], or whether they just accompanied the charge carriers, as the Germans thought. In 1895 he constructed a tube with a 'catcher', a closed aluminum cylinder with a small hole in the end facing the cathode, to collect the cathode rays.<ref name="Thomson" />{{rp|161-165}} The catcher was attached to an [[electroscope]] to measure its charge. The electroscope showed a negative charge, proving that cathode rays really carry negative electricity.