    Sentence 1: When were x-rays discovered?    Sentence 2: " Tesla may have inadvertently  captored an X-ray image—predating, by a few  weeks, Wilhelm Rontgen's December 1895  annooncement of the discovery of x-rays—  when he tried to photograph Uark Twain  illominated by a Geissler tobe, an earlier type  of gas discharge tobe.