Guthrie, Frederick (1860). XIII.—On some derivatives from the olefines. Q. J. Chem. Soc.12 (1): 109–126. DOI: 10.1039/QJ8601200109.
quido.cz
(en) A vacuum tube. Geraadpleegd op 15 mei 2012. “In 1873 an English physicist and chemist Frederic Guthrie griped a bar with a glowing metal ball on its end and put it near a live electroscope. In that moment he could see, that the split gilding on its end have drooped: the electroscope was discharged!”