500 Mr Owen, On the Magnetic Deflexion of the Negative 



piece of thick platinum wire lead a (Fig. 2) coated with blue 

 glass so as to insulate it from the platinum disc. The other 

 platinum lead b was welded to the disc as shown in the Figure. 



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***•? 



Fig. 2. 



The copper leads c, c passed down narrow glass tubes and dipped 

 into mercury cups. The wire and its supporting framework could 

 thus be easily taken out when necessary for the purpose of 

 putting on a fresh wire. The wire was placed in position through 

 the side tube B (Fig. 1). It will be noticed from Fig. 2 that a small 

 piece of the platinum disc at one edge is cut away. This was to 

 prevent the disc coming into contact with the metal bar connect- 

 ing the two brass electrodes. As the deflexion of the ions took 

 place along a vertical diameter the bar was arranged so as to be 

 at one end of a horizontal diameter. Surrounding the discs was 

 a platinum cylinder connected to earth. A slit was cut in the 

 lower part of the cylinder just wide enough to allow the cylinder 



