Stine’s Experiment. Fig. 5,§ 108, p.103.
Stine’s Experiment. Fig. 5,§ 108, p.103.
Stine’s Experiment. Fig. 5,§ 108, p.103.
Stine’s Experiment. Fig. 6,§ 108, p.103.
Stine’s Experiment. Fig. 6,§ 108, p.103.
Stine’s Experiment. Fig. 6,§ 108, p.103.
115.Lodge’s Experiment. X-rays Equally Strong during Fatigue of Glass by Phosphorescence.The Elect., Lon., Apr. 10, ’96.—In order to explain in what way the rays were propagated, he says that it is not as if the glass surface were a wave front from every point of which rays proceed normally, but that the glass radiates X-rays just as a red-hot surface radiates light, namely, a cone of rays starts from each point, and all the rays of each cone start in a different direction. Every point of the glass radiates the rays independently of all other points. Crookes’ Experiment (§ 58) may now be called to mind in reference to the fatiguing of the glass after phosphorescing for a while. Lodge tested the fatiguing as to the power to emit X-rays, but found that there was no such property whatever. The glass which became fatigued as to luminous phosphorescence (§ 105) was not fatigued as to the power ofX-rays. He noticed that the phosphorescent spot became less and less bright, and yet the X-rays remained of the same power.
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§ 112a. 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, andnotconnected 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.”
117.Salvioni’s Experiment. Transposition of Phosphorescent Spot.Elect. Rev., Lon., Apr. 24, ’96, p. 550;Med. Sur. Acad., of Perugia, Italy, Feb. 22, ’96. Personal interview with Prof. Salvioni inElect. Rev., N.Y., Apr. 8, ’96, p. 181.—In order to change the location of the phosphorescent spot when desired, without a magnet, and at the same time to concentrate or intensify the source of X-rays, he placed near the same, on the outside of the tube, the hand or a metal mass connected to earth.The spot immediately jumped to the other side of the tube,§ 49, near centre, and to all appearances was smaller and brighter. Elster and Geitel had performed similar experiments at an earlier date. (SeeWied. Ann., LVI., 12, p. 733, alsoElect. Eng., about April, ’96.) They carried on the most minute investigations as to the deflection of the cathode rays by an outside conductor. Tesla had also noticed a similar deviation. See Martin’sTesla’s Researches. He used alternating currents as described in his system in§ 51. Elster and Geitel used the Tuma Alternating system. (SeeWied. Ann., Ber. 102, part 2A, p. 1352, ’94.) The source from which Salvioni’s description was taken had no sketch, therefore the diagram made by Elster and Geitel is reproduced. See Fig.1. The cathode was aluminum and was connected to one terminal of the transformer. The anode was connected to earth, and also was the other terminal. Upon bringing the hand or other conductor connected to earth to the phosphorescent spot, the cathode rays deviated and the spot jumped over to the other side.§ 50. The anode was a ring surrounding the leading-in wires of the cathode, and the two leading-in wires were surrounded by glass. It may be asked why the cathode rays bent downward in the first place? Elster and Geitel found that they were thrown thus in view of the nearness of some neighboring object connected to earth. To overcome the action of surrounding objects, the tube was surrounded by a ring as shown in Fig.2. However, the rays were still sensitive to objects well connected to earth, and when brought quite close to the tube.
Figs. 1 and 2.
Figs. 1 and 2.
Figs. 1 and 2.
117a.Hammer and Fleming’s Molecular Sciagraph, within a Vacuum Tube.(Citations below.)—In view of the overwhelming evidence concerning the generation of X-rays by the impact of cathode rays, within a high vacuum upon the glass or material which preferably forms the anode, it becomes appropriate, it is thought, to review the state of this department of science, in order to arrive a little more closely at the relations which exist between phenomena of low and high vacua. With the former, in that condition in which striae are formed, permanentblack bands or deposits are produced upon the surface of the glass; the motion of the particles, therefore, appearing to be in planes at right angles to the line joining the anode and cathode.§ 40. That the striae should touch the walls of the tube seems to be necessary for the production of the deposit.§ 44. With a high vacuum, the direction of the cathode rays may be any that one desires, it being only necessary to shape the cathode properly, on the principle that the rays radiate normally from the surface. It is known that the radiation is normal as much from the position of the deposit as from that of the phosphorescent spot. It is certain that they are rectilinear.§ § 57and58. The phosphorescent spot becomes always, sooner or later, when occurring upon the same part of the glass, the location of a deposit from the cathode (§ 123), even when the cathode is aluminum.§ 123. The deposit is not the cause of the fatigue of the glass.§ 58. Puluj verified this. A wheel was made to rotate by the radiations from the cathode, and therefore it is highly probable that the motion of the molecules, which caused the deposit, is the force that made the wheel rotate.§ 58a. Why does it not follow that with increase ofE. M. F.the particles are thrown with such rapidity that upon striking the proper surface (§ 80), X-rays are generated, but that they are not generated when the velocity of the molecules is insufficient.§ 61b, p.46. Attention is now invited to a phenomenon which illustrates that a permanent sciagraph of objects may be impressed upon the inner surface of a vacuum tube, by the deposit of molecules of one of the electrodes. Refer, therefore, to the figure on page30, “Hammer and Fleming’s Molecular Sciagraph.” As will be seen from further explanation and from the picture itself, the sciagrapha bis made because of the projection, in rectilinear lines, of molecules of carbon or metal, from one of the electrodes, or at least from one more than the other. One leg of the carbon, being in the way of the other, causes a less deposit to be produced upon the glass at the intersection of the plane of the horse-shoe filament and the wall of the vacuum tube. Electrodes exist because the filament is of such a high resistance as to produce a difference of potential between the two straight lower portions of the filament. Mr. William J. Hammer possesses a remarkable faculty for observing phenomena often overlooked by others. He first observed a molecular shadow in 1880 and made records of his observations in the Edison Laboratory note book. Since that time he has examined over 600 lamps, which were made at various periods during thirteenor fourteen years, by twelve different manufacturers. (Trans. Amer. Inst. Electrical Eng., Mar. 21, p. 161.) Every one, more or less, exhibited the molecular shadow. It is a principle, therefore, that if the carbon filament has both legs in the same plane, a sciagraph of one of them will be produced. As the shadow is on one side of the bulb only, the molecules fly off from only one electrode, viz., the cathode. By means of photography, the effect is increased because of certain well-known principles. The figure heretofore referred to is taken from a photograph, but, of course, does not represent the sciagraph as well as the original photograph, in view of the loss of effect by re-production by the half-tone process. For further theoretical considerations, see the Institute paper referred to, where the matter was discussed by Profs. Elihu Thomson, Anthony and others. Independently of Mr. Hammer’s discovery, Prof. J. A. Fleming, professor of electrical engineering in the University College, London, England, discovered and studied the matter, and presented it before thePhys. Soc.of London, appearing about 1885 (from memory). The name “molecular sciagraph” is given by the author because it is an accepted explanation that the deposit is due to either molecules or atoms of the electrode, given off by evaporation (page46, lines 5 to 10), or electrical repulsion (§ 61a, lines 22 to 25), or, as some hold, by mere volatilization by the intense heat of incandescence, or one or more combined; but electrical repulsion certainly has something to do with the rectilinear propagation, for the molecules are charged according to§ 4.