242 A. W. Wright — Cathode Bays and their Effects, 



linear, or nearly so, but at a distance of a centimeter, or a little 

 more, from it, they show an outward curvature, which increases 

 with the distance, and their edges become blurred and diffuse, 

 like the rays shown in Lenard's first paper, already quoted, but 

 in a much less degree. Traces of curvature produced by the 

 magnet, appear to be faintly indicated, but if real are very 

 slight. Mutual repulsion of the two streams produced simul- 

 taneously appears to be shown, but the effect is very little. To 

 the eye the three pairs of streams appear to be nearly alike, 

 and even a careful measurement of the angular dimensions of 

 the trails shows but a minute difference, too small to be made 

 the basis for any positive conclusion. 



Within the tube the cathode rays are accompanied by 

 metallic matter derived from the substance of the electrode, 

 and the minute portions of the metal, whether in the form of 

 vapor or fine dust, have been shown by various investigators 

 to be negatively electrified. The electrostatic repulsion of 

 these would be a cause for the mutual repulsion of two cathode 

 streams, as shown in a well-known form of Crookes' tube, 

 while the motion of the electrified masses, causing them to act 

 like an electrical current, as was proved by Eowland,* would 

 render them susceptible to magnetic attractions or repulsions. 

 This also is a familiar observation in respect to cathode streams. 

 Now the glass walls of the tube do not suffer the metallic mat- 

 ter to pass through them, and the metal is deposited upon 

 them, in the form of a sooty coating, or under proper condi- 

 tion, of a mirror-like film of brilliant luster. f Naturally, then, 

 the rays outside of the tube being freed from the metallic 

 matter would* show the effect of mutual repulsion and mag- 

 netic deviation in a less degree, or not at all. If, however, it 

 were possible to make them pass through a metal which would 

 be volatilized by them to some extent, the effects might be 

 expected to reappear. 



To test this point the previous experiment was repeated with 

 this modification : The slits were covered with two layers of 

 ordinary gold leaf, thin enough to transmit light readily, two 

 being used to lessen the chance of small rifts permitting the 

 rays to pass unimpeded and to interfere with the result. To 

 compensate for the lessened effect of the rays, caused by the 

 gold leaf, the vacuum-tube was brought a little nearer the slit- 

 plate, to a distance of 97 mm . Otherwise the arrangement and 

 adjustment were exactly as before, and the exposures were 

 made in the same manner, but were slightly longer, 40 minutes 

 each. Gold was selected for this experiment for the reason 

 that it had been found, in earlier experiments by the writer,:); 



* This Journal, III, xii, p. 390, 1876; xv, p. 30, 1878. 



\ This Journal, III, vol. xiii, Jan.. 1876, p. 49 ; vol. xiv, Sept. 1877, p. 169. 



X This Journal, loc. cit. 



