134 Photographic Action inside Discharge Tubes, 



set the two cylinders surrounded by black paper, the one in 

 the first compartment the other in the second respectively* 

 The two compartments were meanwhile exhausted by the 

 same pump. The results were the same as in the preceding 

 experiments. But to place beyond any doubt that the photo- 

 graphic action was due to the paper struck by the kathodic 

 rays, I fixed on the paper surrounding the cylinders some 

 glass threads of various thickness and quality. 



As glass is known to emit the ^-rays as well as paper 

 when it is struck by the kathode-rays, it follows that the said 

 threads should appear as lines of greater impression on the 

 photographic plate. 



On the contrary, in all the experiments I have conducted 

 I always obtained on the film well-marked shadows of the 

 glass threads. They are little less perceptible than those of 

 iron or copper wires. 



Thin glass plates also, about 1/10 of a millimetre thick, cast 

 their shadow on the photographic film. 



There remains still a remarkable difference observed by 

 Rontgen between the ^-rays and the kathodic rays, namely, 

 that the A'-rays are not deflected by the magnet, while the 

 kathodic rays are. 



Also on this point I have had recourse to experiment. 



1 constructed a tube of a spherical form in which the 

 kathode and anode were placed within two tubes situated along 

 the same diameter of the sphere. A cylinder surrounded by 

 a photographic film, protected by black paper, was introduced 

 into the sphere through the stem and suspended there within 

 the upper hemisphere. A strong electromagnet was fixed on 

 the sides before the lower hemisphere, so that the kathodic 

 rays were strongly deflected. From what the eye could per- 

 ceive they touched slightly the inferior brim of the sensitive 

 cylinder. 



The different experiments conducted all gave a strong 

 action on the film on the face turned towards the kathode, and 

 a less strong one on the face turned to the fluorescent disk 

 struck by the kathodic rays, and no action at all on the rest 

 of the surface. 



We must then conclude that the rays which inside the tube 

 are capable of photographic action are not (at least a part of 

 them) deflected by the magnet. 



Then I introduced into the spherical tube a sensitive 

 cylinder which occupied the whole height of the sphere, and 

 applied the magnet to the same place as before. The films 

 when developed showed that the photographic action was 

 much more intense in the region to which the kathodic rays 



