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XIX. Researches on Photographic Action inside Discharge 

 Tubes. By Angelo Battelli*. 



THE great similarity that exists between the action of the 

 a?-rays and the action that Herr Lenard, of Hungary, 

 obtained with tubes having one end closed with aluminium, 

 induces us to suppose that the kathodic rays may directly pro- 

 duce within the tube both photographic action and electric 

 dispersion. 



To demonstrate the photographic action a cylindrical tube 

 was used, having sealed to it near the middle a wide glass 

 stem (C). Through the said glass stem was introduced into 

 the tube a photographic film, surrounded by black paper, and 

 placed on a metallic cylinder. Four different designs of wire 

 were fixed longitudinally on the roll of black paper, upon 

 four lines placed at a distance of 90° the one from the other, 

 so that one design faced the kathode or negative pole, another 

 the anode or positive pole, and the other two designs the 

 lateral walls of the tube. 



In all the experiments made a very strong impression 

 occurred on the face turned to the kathode, and a very slight 

 one on the other faces of the film. 



We might, however, explain the fact by assuming that the 

 kathodic rays striking on the sheet of black paper made it 

 apt to emit the #-rays with greater efficiency than the end of 

 the tube, which is more distant from the kathode and the 

 photographic film than the black paper. 



To meet this objection I tried, first of all, placing two 

 similar sensitive cylinders the one inside the tube, the other 

 outside it, in order to have the two anterior faces of the films 

 in very nearly the same condition, the first in relation to the 

 end of the tube, the second in relation to the black paper ; 

 that is, I placed two of the cylinders before-mentioned in 

 connexion with the end of the tube exposed to the kathodic 

 rays, but the one inside it and the other outside. 



It resulted that the face of the film turned to the kathode 

 remained strongly acted on after a very short exposure, while 

 the exterior film showed a very feeble impression. 



To render the condition of the inner film still more similar 

 to that of the exterior one, I constructed a double tube 

 divided by the means of a glass partition into two longitudinal 

 compartments. The first compartment contained the anode 

 and kathode, and on the two faces of the glass partition were 



* Communicated by the Author 



