and have had a large impact on the development of many instruments and devices which depend on electric discharge through gases. One of the most significant consequences of Geissler tube technology was the discovery of the electron and the invention of electronic vacuum tubes. By the 1870s better vacuum pumps enabled scientists to evacuate Geissler tubes to a higher vacuum; these were called Crookes tubes after William Crookes. When current was applied, it was found that the glass envelope of these tubes would glow at the end opposite to the cathode. Observing that sharp-edged shadows were cast on the glowing tube wall by obstructions in the tube in front of the cathode, Johann Hittorf realized that the glow was caused by some type of ray travelling in straight lines through the tube from the cathode. These were named cathode rays. In 1897 J. J. Thomson showed that cathode rays consisted of a previously unknown particle, which was named the electron. The technology of controlling electron beams resulted in the invention of the amplifying vacuum tube in 1907, which created the field of electronics and dominated it for 50 years, and the cathode ray tube which was used in radar and television displays. Some of the devices which evolved from Geissler tube technology: Vacuum tubes Xenon flash lamps (for flash photography) Xenon arc lamps (for movie and IMAX projectors) X-ray tubes Sodium vapor lamps used in streetlights "Neon" signs, which use both visible light discharge from neon and other gases and phosphor excitation from ultraviolet light Mercury vapor lamps Mass spectrometers Cathode ray tubes, employed in the oscilloscope and later in television sets, radar, and computer display devices Electrotachyscope (an early moving picture display device) Fluorescent lamps Plasma globes See also William Crookes Cathode ray tube Crookes tube Induction coil Neon sign Plasma globe X-ray tube German inventions and discoveries References External links Sparkmuseum: Crookes and Geissler Tubes Instruments for Natural Philosophy: Geissler Tubes Mike's Electric Stuff: Geissler Tubes The Cathode Ray Tube site Geissler and Crookes tubes shown working How to Make an Experimental Geissler Tube, Popular Science monthly, February 1919, Unnumbered page, Scanned by Google Books. Vacuum tube displays Gas discharge lamps German inventions