1898.] on Some New Studies in Cathode and Rontgen Radiations. 501 



In any ca^e tlie photographs that I have shown you prove very 

 conclusively that those negative atoms which are least deflected by a 

 magnet are tliose which produce the most active Rontgen rays, and 

 therefore it follows that the quality of the Rontgen rays is very 

 largely dependent upon the velocity with which the negative atoms 

 strike upon the anti-cathode. Quite in harmony with this theory is 

 an exj^eriment which I will now show you. I have here a Rontgen 

 ray tube with two cathodes, as shown in Fig. 11. The cathodes are 

 both in the same tube, and therefore the conditions as regards vacuum 

 nuist be the same for both. They both focus upon opposite sides of 

 the same platinum anti-cathode, and they only differ in the fact that 



Fig. 11. 

 Focus tube with two cathodes of differeut diameters. 



one is considerably larger than the other. I will now put the tube 

 into operation, using the larger cathode, and as you see, scarcely any 

 Rontgen rays are pi'oduced, while what there are do not jienetrate 

 my hand. I will now alter the connections and use the smaller cathode 

 instead of the larger one. Now very penetrative Rontgen rays are 

 generated in abundance, and you can clearly see the shadow of the 

 bones in my hand on the fluorescent screen. 



Here is another tube which is furnished uith four cathod s all of 

 different sizes and all arranged to focus upon the same anti-cathode, 

 which can be rotated so as to face the particular cathode in use. This 

 tube behaves just like the other, and for any given degree of exhau^-tion 

 gives more penetrative Rontgen rays the smaller the cathode employed, 



