THE CATHODE RAY OSCILLOGRAPH 7 



mined that cathode rays have mass as well as charge. Thomson's 

 tube ^ is shown in Fig. 7. 



The Braun tube immediately found many applications. One of the 

 most fruitful fields for it was its use by Professor Zenneck in studying 

 radio circuits and the transmission of radio waves. From Professor 

 Zenneck and his school there are still papers coming out on work done 

 by means of the Braun tube. The tube was introduced in this country 



Fig. 8— Ebert and Hoffmann, 1898— tube by Geissler.^ 



very early. Professor H. J. Ryan, then at Cornell, in 1903 described 

 measurements on high voltage power circuits, and similar work has 

 appeared occasionally ever since from Professor Ryan's hand. 



After the invention of the tube there were a number of improve- 

 ments that made it more convenient and its operation more reliable. 

 Figures 8-12 show some of the many designs of tubes of this time. 



* Thomson, J. J., Phil. Mag., 44, p. 293, 1897. 

 6 Ebert and Hoffmann, E. T. Z., 19. p. 405, 1898. 



