124. FLUORESCENT LAMP. In an English patent of ’82, granted to Rankin Kennedy, there is described a vacuum bulb in which the electrodes are covered with fluorescent or phosphorescent substances, intended for the purpose of obtaining greater candle power by impact of cathode rays upon anode of platinum, covered with alumina or magnesia. Edison coated the inner wall of the discharge tube, for generating X-rays, with calcic tungstate in the crystalline form. The luminosity, when measured, amounted to about 2-1/2 C. P. As to the efficiency, he stated that this was accomplished “with an extremely small amount of energy.” Such a coating was found to weaken the X-rays radiated therefrom, which, of course, was natural, because they had been converted into phosphorescent light. The spectrum showed strongly at the red line, thereby suggesting the reason why the light was of a pleasant character. 124_a_. PILTCHIKOFF’S EXPERIMENT. Greater emission of X-rays by a tube containing an easily fluorescent substance. _Comptes Rendus_, Feb., 24, ’96. From trans. by Mr. Louis M. Pignolet. As the X-rays emanate from the fluorescent spots on the glass of the discharge tube, he reasoned that more powerful effects would be obtained by replacing the glass by a more fluorescent material. He therefore tried a Puluj tube and found that it shortened the time necessary for taking a photograph in a “singular” degree. Experiments of others have certainly shown that as phosphorescence decreases with increase of vacuum, the X-rays increase to a certain maximum, § 105. Let it be noticed however, that this does not prove that with the same vacuum, an increase of phosphorescence by a superior phosphorescent material of equal thickness would not increase the power of the X-rays. The best way to determine such points, is to go to extremes. Edison applied so much easily phosphorescent material (calcic tungstate) to the inside of the discharge tube, that much light was radiated, but only feeble X-rays. On the other hand, without any of the tungstate, the rays were strong, § 124. Experiments generally tend to prove that it depends upon the chemical nature of the material rather than its phosphorescing power, in other words upon the permeability. § 119, near end. 125. ELECTRODES OF SILICON CARBIDE. (Carborundum.) Edison called attention to Tesla’s discovery that this substance is a good conductor for high tension currents. Its advantages for electrodes in the discharge tube are its high conductivity, no absorbed nor released gas bubbles, and its infusibility and non-blackening power of glass even when the voltage was increased to a point where the glass melted. [Illustration: EDISON (AT RIGHT) AND T. COMMERFORD MARTIN USING THE SCIASCOPE. § 97, p. 84. Cut also shows Sprengel vacuum-pump. Discharge-tube is in the box. ]