116. ROWLAND, CARMICHAEL AND BRIGGS’ EXPERIMENT. AREA STRUCK BY CATHODE RAYS ONLY AN EFFICIENT SOURCE WHEN POSITIVELY ELECTRIFIED. _Electricity_, N.Y., Apr. 22, ’96, p. 219.—Experiments carried on at the Johns Hopkins University led the above named investigators to think at first that the source of the X-rays was at the anode. _Amer. Jour. Sci._, March, ’96. Prof. Elihu Thomson was led to give the same opinion during his first experiments. _Elect. Rev._, N.Y., Mar. 25, ’96. See also § 112_a_. Many other experiments certify to the allegation that X-rays are certainly generated at the phosphorescent spot on the glass. § 79, 105, 107, 108, 111, 112, 113. From the experiments of Prof. Rowland, _et al._, the confusion is accounted for by the fact that they overlooked the electrical condition of the spot struck by the cathode rays. Prof. Rowland, _et al._, constructed a tube having a platinum sheet located at the focus of the concave electrode, and _not_ connected to the anode. Although the platinum became red hot, it emitted no X-rays, but when the platinum was made the anode, there was profuse radiation of X-rays in all directions from that side of the platinum struck by the cathode rays, and no radiation from the other side. § 91. (See also Roentgen and Tesla, concerning 1/2 platinum and 1/2 aluminum and radiation therefrom.) They inferred as a final conclusion in connection with this point, “That the necessary condition for the production of X-rays is an anode bombardment by the cathode discharge.” § 113. They recognized apparently that it had been conclusively proved that X-rays radiated from the phosphorescent spot on the glass. They held that such a spot is “The induced anode formed on the glass.” § 49, at end. They did not prove this by an experiment according to the article referred to, but based it upon “The fact that the bombarding cathode rays coming in periodical electrified showers alternately raise and lower the potential of the glass, thus making it alternately an anode and a cathode. In the case of the platinum, this could not occur to the same extent.”