University of Maryland Baltimore Dental School - Mirror Yearbook (Baltimore, MD)

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1650 Otto Von Guericke invented the first air pump, later used to produce a vacuum in a Crookes ' Tube. 1831 Michael Faraday discovered the process of electromagnetic induction by the relative motion of a magnet and a conducting wire. Without the application of this profoundly important principle to the induction coil and high-voltage electric currents, the present use of X-rays would be impossible. 1831-1856 Period of transition in early design of static machines, induction coils and transformers for producing high voltage. 1837 Michael Faraday experimented with rarefied gases producing luminous effects created by electric discharges through these media. 18 51 Ruhmkorff produced the first induction coil, later used for energizing the X-ray tube. 18 57 Heinrich Geissler, a German scientist of the City of Bonn, constructed the first vacuum tube and noticed that an electrical discharge passed through a vacuum tube produced a glowing. This was termed fluorescence. 1865 Herman Sprengel invented the mercury air pump the use of which resulted in the production of high rarefactions with comparative rapidity. 1874 Original Crookes ' Tube demonstrated by Sir William Crookes. 187 5 Sir William Crookes, an eminent English scientist, exhausted tubes to approximately one-millionth of an atmosphere pressure, the degree of vacuum necessary for the production of the X-ray. 1873 Sir William Crookes discovered that high voltage electric current, in its passage through a highly evacuated tube, was being carried by a stream of radiant particles, originating at the negative terminal. These were later called cathode rays. 1888 Professor Heinrich Hertz succeeded in proving a mathematical proposition stated by Maxwell in 1866: that an electrical disturbance should develop waves in the ether. Lenard, a pupil of Hertz, demonstrated the effect of the cathode rays on crystals of barium platinocyanide and sensitive photographic plate. 1895 November 8. Roentgen ' s observation was made on a Friday evening, while he was working alone in his laboratory. When the room was darkened and the current turned on. Roentgen noted a fluorescence emitting from a barium platinocyanide screen on the wall some distance from the Crookes ' Tube. While walking toward the screen, Roentgen crossed the path of the rays and noticed the shadow of his hand appearing on the coated side of the screen. The fluorescence on the s;reen was not of prime importance — it was the fluores- cence of the screen in the shadow which attracted Roentgen ' s attention, and his following up this first observation yielded the discovery of the X-ray. First demonstrated roentgenogram: weights in closed wooden box. 1896 January. Dr. Otto Walkhoff, a dentist of Braunschweig, Germany, made the first dental radiograph; exposure time was 2 5 minutes. February. The first X-ray picture of the teeth was exhibited by Professor Koenig to the Society of Physics at Frankfurt, Germany. April. Dr. William James Morton, of New York, made the first dental radiograph in the United States, and was followed soon by Drs. Van Woert, Ottolengui, and C. Edmund Kells. June. X-rays first mentioned in American dental literature. Kirk, Edward C; Editorial {Dental Cosmos) and Morton, William J.; X-ray and Its Application to Dentistry. (Dental Cosmos). August. Dr. C. Edmund Kells, of New Orleans, gave the first dental X-ray Clinic ever held in the United States, at Asheville, N. C. After a period of constant devotion to the development of radiodontia Dr. Kells died a martyr to the cause. Professor Jackson of Kings College, London, invented the first single-focus tube for X-ray work. 1896-1898 Caustic potash bulb used to regulate amount of current. Concave aluminum cathode used in some of the first tubes. 1896-1913 Period of transition in the design and manufacture of gas X-ray tubes, rectifiers, rotary converters and spark gaps, advancing from the Telsa transformer, high-frequency type of machine, and induction coil type to the more modern oil immersed transformer type which became more popular with the advent of the Coolidge Tube. 1897 June. Dr. Van Woert was the first person in America to use a filin intraorally. ' 1899 Ruhmkorff Coil built especially for Roentgen-ray work. Thomson and Tesla experimented with the high-frequency alternating current and found that with a very high oscillation the current would excite the single-focus tube and not produce the undesirable heating effects. Ramney-Wimshurt-Holtz Static Electric Machine: current source for excitation of Crookes ' Tube. Double-focus vacuum tubes replaced the single-focus type to compensate for the change of current, i.e., D.C. to A.C. (Continued on next page)