Polarized light, he reminded them, produced similar results upon selenium. Although the domain of this book is necessarily limited to the consideration of phenomena connected with the internal and external energy of a discharge tube, yet if any other one subject is of special interest and utility in connection with the consideration of X-rays, it is that concerning the relation between the electric discharge and light, which has been thoroughly studied only during the past few years, and the accounts of the researches recorded in various periodicals and academy papers. Those readers, however, who desire to study this exceedingly interesting and novel branch of science, which in connection with the action of the internal cathode rays and X-rays upon electrified bodies, tends to uphold Maxwell’s theory as developed by mathematics and based upon early known facts and predicted discoveries, may find volumes upon this subject by referring to the citations below, named by Mr. N. D. C. Hodges and obtained by him by a search in the archives of the Astor Library. Of especial interest are those of Branly, § 99_I_, 99_J_, 99_Q_, 99_S_, 99_T_. Some notion as to the contents of the citations are given here and there. 99_A_. KOCH’S EXPERIMENT. THE LOSS OF ELECTRICITY FROM A GLOWING ELECTRIFIED BODY. _Wied. Ann._, XXXIII., p. 454, ’88. 99_B_. SCHUSTER AND ANPENIUS’ EXPERIMENT. THE INFLUENCE OF LIGHT ON ELECTROSTATICALLY CHARGED BODIES. _Proc. R. So._, Lon., LXII., p. 371, ’87; _Proc. Swedish Acad._, LXIV., p. 405, ’87.—Many recent periodicals have set forth that ultra-violet light will discharge only negatively charged bodies. While this is practically or sometimes the case, yet these experimenters found that a positive charge was dissipated very slowly. They confirmed the results that the ultra-violet rays played the principle part in the removal of a negative charge. Polishing the surface accelerated the action. § 99, near beginning. 99_C_. RIGHI’S EXPERIMENT. SOME NEW ELECTRIC PHENOMENA PRODUCED BY LIGHT. Note 2-4, _Rend. R. Acad. die Lincei_, May 6, 20, and June 3, ’88. 99_D_. RIGHI’S EXPERIMENT. SOME NEW ELECTRIC PHENOMENA PRODUCED BY ILLUMINATION. _Rend. R. Acad. die Lincei._ VI., p. 135, 187, ’88.—Confirmation of the results of other physicists, and a quantitative measurement determining that the E. M. F. between copper and selenium was increased 25 per cent. by illumination by an arc light. The selenium was in the form of crystals mounted upon a metal plate. 99_E_. STOLSTOW’S EXPERIMENT. ACTINO-CURRENT THROUGH AIR. _C. R._, CVI., pp. 1593 to 95, ’88.—Liquids tested. Greatest absorbents of active rays most quickly discharged. 99_F_. RIGHI AND STOLSTOW’S EXPERIMENTS. KIND OF ELECTRIC CURRENT PRODUCED BY ULTRA-VIOLET RAYS. _C. R._, CVI, pp. 1149 to 52, ’88.—The discharge was accelerated by using a chemically clean surface. The burning of metals, for example, aluminum, zinc or lead in the arc light increased the discharging power.