LONDON. Rontgen Society, January 1.—Capt. G. W. C. Kaye, president, in the chair.—Dr. W. D. Coolidge: A “radiator” type of X-ray tube. The anticathode consists of a block of copper faced with a small button of tungsten. This is fixed to a thick stem of copper which passes. out through the glass neck of the tube and terminates in a fin radiator. The anticathode is thus kept cool and does not in consequence emit electrons, as in the case of the earlier type of Coolidge tube in which the whole of the anode speedily becomes red-hot. The new tube, therefore, so completely rectifies current that when an alternating potential is applied the current will only pass in one direction.—Dr. W. D. Coolidge and C. N. Moore: The field X-ray outfit of the United States Army. A petrol-electric unit supplies alternating current at no volts to a transformer arranged to give both high-tension and heating currents for the new radiator type of Coolidge tube. For simplicity of control the tube is worked at a constant potential of:; in. equivalent spark-gap, and the current is adjusted to 5 milliamperes for continuous running of the tube or to 10 milliamperes for short periods. An electrically actuated control on the throttle of the engine maintains constant output. The small size of the bulb, 35 in. in diameter, enables a close-fitting lead-glass shield to be employed. This is made in two parts, and completely surrounds the tube, a suitable aperture permitting egress of the useful rays.