    Sentence 1: What were X-rays known as at the time?    Sentence 2: In March 1896, after hearing of Wilhelm  Réntgen's discovery of X-ray and X-ray imaging  (radiography), Tesla proceeded to do his own  experiments in X-ray imaging, developing a high  energy single terminal vacuum tube of his own design  that had no target electrode and that worked from the  output of the Tesla Coil (the modem term for the  phenomenon produced by this device is  bremsstrahlung or braking radiation).