he placed the same in a highly exhausted bulb and found that the discharge was in one case, for example, only 1/70 as rapid as in air and hydrogen at ordinary pressure, thereby serving as another proof that gas was the intermediate agency. Allowance should be made in all experiments in connection with the discharging quality of X-rays. The surrounding gas should be taken into account. 90_a_. APPLICATION OF PRINCIPLE OF DISCHARGE BY X-RAYS.—Professor Robb, of Trinity College, (_Science_, Apr. 10, ’96), proposed and explained and practically tested the principle of the discharge of X-rays to determine the relative transparencies of substances to X-rays. He plotted a curve in which the co-ordinate represented the charge of the condenser in micro-coulombs, and the abscissæ the time between charging and discharging the condenser. The same plan could be adopted, he suggested, for making quantitative measurements of the intensity of X-rays from different tubes or the same discharge tube at different times. J. J. Borgmann, of St. Petersburg, probably was the first to show that X-rays charged as well as discharged bodies. See _The Elect._, Lon., Feb. 14, ’96, p. 501. Soon, a similar announcement was made by Prof. Righi, of Bologna. § 90. 90_A_. BORGMANN AND GERCHUN’S EXPERIMENTS. ACTION OF THE X-RAYS ON ELECTRO-STATIC CHARGES AND (LA DISTANCE EXPLOSIVE.) _Comptes Rendus_, Feb. 17, ’96; from _Trans._, by Louis M. Pignolet.—A positively charged zinc disk connected to an electroscope lost its charge almost instantly and acquired a negative charge. When the charge on the zinc disk was negative, the loss was much slower and was not complete, a certain charge remaining. When the rays fell upon two small platinum balls connected to the terminals of an induction coil but separated beyond its sparking distance, sparking took place between them, showing that X-rays, like ultra-violet rays, increase the sparking distance of static charges. 90_b_. RIGHI’S EXPERIMENTS. BODIES IN THE NEUTRAL OR NEGATIVE STATE, POSITIVELY ELECTRIFIED BY X-RAYS. _Comptes Rendus_, Feb. 17, 1896. From Trans. by Louis M. Pignolet.—The measurements were made by this eminent Italian physicist, with a Mascart electrometer connected with the bodies upon which the X-rays impinged and enclosed in a grounded metallic case (Faraday cylinder) provided with an aluminum window for the entrance of the rays. A metallic disk connected with the electrometer lost its charge rapidly whether positive or negative.