1896.] 



on Electric Shadows and Luminescence. 



203 



means of vacuum-tight cement. 



its form being that shown in Fig. 5. The kathode was a flat disk on 

 the end of a ghxss-covered wire stem. The anode was a cylindrical 

 tube of brass surrounding the kathode. Upon the farther end of 

 the tube a brass cap was fixed by 

 Over a small orifice in this 

 brass cap was set the alumin- 

 ium window of foil only ^i^ 

 millimetre thick. By this 

 means he was able to do what 

 had previously been supposed 

 impossible, bring the kathode 

 rays out into the open air. Or, 

 at least, that is what he ap- 

 pears to have considered that 



he was doing. Certainly he succeeded in bringing out from the 

 vacuum tube rays that, if not actual prolongations of the kathode 

 rays, were closely identified with them. He examined their proper- 

 ties both in the open air and in gases contained in a second chamber 

 beyond the window, and 

 found them to be capable of 

 producing photographic im- 

 pressions on sensitive i)lates. 

 He further examined the ques- 

 tion whether they can be de- 

 flected by a magnet. Fig. 6, 

 which is copied from Lenard's 

 paper, shows the results. The 

 row of spots on the left side 

 shows the photograj^hic effect 

 under various different condi- 

 tions of experiment when there 

 was no magnet present. The 

 spots in the right-hand row 

 show the effects obtained when 

 a magnet was present. For 

 example, in the third row from 

 the top it is seen that the 

 bundle of rays when subjected 

 to the influence of the magnet 

 is partially dispersed, the spot 

 being enlarged sideways and 

 having a kind of nebulous tail. 

 This proves that through the 

 aluminium window there came 

 some rays which were deflected by a magnet, and some rays also 

 which were not deflected by a magnet. The question naturally arises 

 whether the rays which Lenard had thus succeeded in bringing out 

 into the open air are the same thing as the rays with which Crookes 



Fig. 6. 



