The London, Edinburgh and Dublin philosophical magazine and journal of science . was noted when theinduction-coil was not working, so that this measured thespontaneous ionization of the air. When the bulb was workedthe leaf fell much more rapidly. The aperture A (fig. 2) in the box was then covered withlead, and the effect on the electroscope was again normal,showing that the rapid fall was not due to direct radiationthrough the lead covering of the box inclosing the bulb andinduction-coil and through the second opening B to the paperface of the electroscope. The effect was therefore causedby
The London, Edinburgh and Dublin philosophical magazine and journal of science . was noted when theinduction-coil was not working, so that this measured thespontaneous ionization of the air. When the bulb was workedthe leaf fell much more rapidly. The aperture A (fig. 2) in the box was then covered withlead, and the effect on the electroscope was again normal,showing that the rapid fall was not due to direct radiationthrough the lead covering of the box inclosing the bulb andinduction-coil and through the second opening B to the paperface of the electroscope. The effect was therefore causedby radiation proceeding through A. When B was covered with lead the motion of the gold-leaf was again normal,, so that the fall was not due to directradiation from A through the lead of the screen. The electroscope being out of the direct beam, the leak wasdue indirectly to radiation passing through A and B. Radiation from Gases subject to 689 When the length of the aperture B was kept constant andthe width altered, the rate of motion of the gold-leaf was Fig. 2. Ea/?th. £a*7H approximately proportional to the width of the slit and there-fore to the breadth of the beam. This proved that the effectwas not due to secondary radiation from the edges of thelead round B, for when the slit was very narrow, doublingits width added little to the length of the edge, while themotion of the gold-leaf was twice as rapid. The same thing was also proved by screening the paperface of the electroscope from direct radiation from B by asheet of lead, which was so arranged as to intercept verylittle radiation proceeding from the air through which theprimary beam passed. When the paper face was covered with a sheet of lead, theelectroscope was perfectly screened. It was at first (when very thin paper was used for the faceof the electroscope) doubtful whether some of the ions formedin the air by the primary radiation were not pulled throughpores in the paper into the electroscope. The paper w
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Keywords: ., bookcentury1800, bookdecade1840, bookidlondon, booksubjectscience
