Rays of Positive Electricity. 765 



there was a well-marked spot which was visible on both the 

 positive and negative side (this is the spot / in fig. 8). 

 When the conditions were most favourable to accurate 

 measurements, it was found that increasing the potential 

 difference between the plates from 100 to 200 volts increased 

 the horizontal deflexion of the spot by 3 millimetres when 

 the second system of plates was used. While an increase of 

 3 millimetres in the vertical deflexion was produced by 

 increasing the current through the electromagnet by 

 1 ampere. The measurements of the magnetic induction 

 by the flnxmeter showed that this increase in the current 

 corresponded to an increase of 5'05 x 10 l in the value of 





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ence we have 







•3=- x5-05xl0 3 , 

 mv 





Q e v 1010 *9 



•3= — , x — =- x 62 

 mv* 6 



iving 



^=2-1 x 10 s , 





e/m = 1-24 X 10 4 . 



It was found that the values of e/m for this spot always 

 came out a little greater than 10 4 , and as the spot was not 

 quite at the extreme end of the straight band of phosphor- 

 escence due to the secondary rays, the value of e/m for the 

 rays at the tip of this band would be still greater; for the tip 

 the values of e\m ranged up to 1*5 X 10 4 , but as the tip is 

 somewhat ill-defined the values of e/m for it could not be 

 measured with the same accuracy as when there was a spot. 

 The larger values of e/m were more frequent for the negative 

 secondary rays than for the positive ones ; these larger values 

 would be accounted for if some of the particles had acquired 

 a double charge for part of their course. 



For the spot e the magnetic deflexion for a currant 'of 

 2 amperes through the electromagnet 



(value of ( (l-x)Hdx=Vl x 10 4 ) 



Jo 



was 4*4 millimetres, and for 200 volts an electrostatic 



