306 



ILLINOIS STATE ACADEMY OF SCIENCE 



PRELIMINARY NOTE ON THE ELECTROMAGNETIC 



INDUCTIVE PROPERTIES OF A CATHODE 



RAY SOLENOID 



Prof. Chas. T. Knipp and C. S. Palmer 

 University of Illinois 



That a cathode ray solenoid should possess electromag- 

 netic inductive properties of a magnitude that can be meas- 

 ured (or rather detected) by a suitably high sensitivity 

 galvanometer has been more or less apparent to one of the 

 writers for a number of years. It was suggested by Row- 

 land's classical experiments on the equivalence of a moving 

 charge to a current of electricity. However, it was not until 

 recently that it was decided to put the experiment to a 

 test. That the electron composing the cathode ray beam 

 is deflected by either an electrostatic or a magnetic field is 

 well known, and, in itself, is evidence enough of its equiv- 

 alence. If now the cathode ray beam be used to induce a 

 current in a neighboring wire through its purely electro- 

 magnetic action, then such an induced current should be re- 

 garded as additional evidence of the equivalence of a moving 

 charge to a current of electricity. 



The arrangement of the apparatus, Fig. 1, proposed to 

 test this point, is to form within a suitably designed cathode 

 ray discharge tube, by means of a powerful external mag- 

 netic field (in which H is of the order 50 gausses), a cathode 

 ray solenoid having the approximate dimensions: length, 



Po^frfi^ MogngfiTin^ Fte/d 



3tQ Oarrr 



C lectrom aqnetic Inductive Cath ode Raij Solenoid 



FIGURE 1. 



40 cm. ; diameter, 2 cm. ; and pitch, 1 cm. This solenoidal 

 beam is made to pass through a glass tube, which is an 



