CHT237259 Bunsen-Kirchoff Spectroscope invented by Robert Bunsen (1811-99) and Gustav Kirchoff (1824-87) in 1859 (engraving) (b/w photo) by German School, (19th century); Bibliotheque Nationale, Paris, France; (add.info.: discovered two alkali metals, cesium and rubidium using spectroscope in 1860;); 穢 Archives Charmet; German, out of copyright.